TECHNICAL FIELD

[001] The present disclosure relates to a method and arrangement for balancing a gas flow system comprising a plurality of gas flow inlets and/or outlets.

BACKGROUND ART

[002] Every time a building is being constructed or renovated the ventilation system needs to be balanced. Balancing a ventilation system is hard, takes a lot of time and expertise to get right. Usually, a ventilation system comprises many outlets and inlets. In each outlet/inlet there is a product (permanent device which works like a valve) which needs to be adjusted correctly to fulfil the ventilation requirements.

[003] Traditionally, balancing of ventilation systems requires an operator to measure and manually adjust each product at every outlet iteratively to reach satisfactory settings of the products controlling the airflow. Such procedure requires intense and laborious manual labour and a lot of experience to be able to carry out the balancing fast and to achieve optimal settings.

[004] In US10671098 is described a method for balancing terminals of an HVAC system using an air flow measuring device, comprising: inputting into a computer processing portion of the air flow measuring device a predetermined target flow for each terminal, and acquiring via the air flow measuring device an initially measured air flow through each terminal, the initially measured air flow through each terminal being provided to the computer processing portion; and adjusting each terminal in the HVAC system to a calculated flow set point according to instructions from the computer processing portion, the computer processing portion being programmed to determine the calculated flow set point for each terminal that results in each terminal being set to its respective predetermined target flow after all terminals in the HVAC system have been adjusted as instructed by the computer processing portion.

[005] When taking a measurement at a time, the balancing method becomes prone to errors due to surrounding conditions. If a confined space becomes unconfined due to a door or window being opened, the change in ambient pressure is difficult to notice and this causes incorrect flows if the gas system is being balanced one valve at a time. One might work around this problem if measuring every point for a long time, but this makes the process laborious. [006] In EP3611437A1 is described a method and system for balancing a ventilation system wirelessly by temporarily replacing the permanent control components with a portable, detachable adjustment component. In this document, a damper setting value is calculated and this is used in order to balance the ventilation system. The system is configured to send the calculated damper settings to all the active adjustment components at the same time and then waits for them to adjust and send new operational data. Based on the new operational data at the calculated damper setting the process iterates over again. This causes operational conditions to change unpredictably and therefore optimal settings will not be reached. Only if the measured operation data fulfils specified conditions within a set number of iterations the system is considered to be in balance, otherwise an operator is requested for new damper settings via a display.

[007] Other methods include using sensors in order to monitor the state of the gas flow system, but still require users to in an iterative way manually balance and re-calculate system parameters after each adjustment.

[008] Other known methods base their adjustment strategies on an index and or reference valve within the system, which makes the balancing process prone to anomalies and outer interference at said index and or reference valve. If the index and or reference valve for example turns out to have been wrongly selected by the user, or has been subject to outer interference during the balancing process, or is badly installed, the entire balancing process may have to be re-done.

[009] Other existing methods have pointed out the large error one might get by using k- factors from the manufacturer for calculating flows over valves. This might be solved by measuring in field a more exact k-factor, which can then be used by sensors to calculate a more accurate flow while balancing the gas flow system. Even though this yields more exact results, it also leads to a more laborious working method for the operator, who must do these re-calculations of k-factors every time a valve is to be adjusted.

[0010] There is, hence, a need to be able to carry out a balancing process in a more robust way. SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide a method and arrangement for balancing a gas flow system in a more robust way than with existing methods and arrangements.

[0012] According to a first aspect there is provided a method for balancing a gas flow system comprising a plurality of gas flow inlets and/or outlets. The method comprises to arrange a balancing unit at a respective of at least two gas flow inlets/outlets of the gas flow system, wherein the balancing unit is arranged as a valve or damper in a gas flow inlet/outlet or arranged at a permanent valve or damper in a gas flow inlet/outlet in the gas flow system, wherein each balancing unit comprises a gas flow measuring unit arranged to measure a gas flow through the respective gas flow inlet/outlet. A system controller is provided and each balancing unit is wirelessly connected with the system controller. For each gas flow inlet/outlet provided with a balancing unit, a desired gas flow through the gas flow inlet/outlet is provided to the system controller. Gas is supplied to the gas flow system, and by means of the gas flow measuring device of each balancing unit, a gas flow is measured through each respective gas flow inlet/outlet when the balancing unit and/or the permanent valve are set in a respective first mode, and the system controller, through said wireless connection, is provided with the measured gas flows. In the system controller, based on the measured gas flows and the desired gas flows, for each gas flow inlet/outlet a condition parameter is calculated, and the calculated condition parameters compared for all gas flow inlets/outlets, and based on the comparison, a reference gas flow inlet/outlet is identified. The gas flow through at least some of the gas flow inlets/outlets is adjusted, one or more at a time, during which adjustment the respective condition parameter and the condition parameter of the reference gas flow inlet/outlet are re-calculated at least once, the adjustment being performed by changing each balancing unit and/or permanent valve from their respective first modes into a respective second, balanced mode, in which balanced mode the re-calculated condition parameter for a gas flow inlet/outlet is substantially the same as a re-calculated condition parameter of the reference gas flow inlet/outlet.

[0013] The gas flow system to be balanced may for example be an air ventilation system, such as in a residential building, in an industrial property, in a warehouse or in any type of building in which a ventilation system comprising a plurality of airflow inlets/outlets, nodes, has been installed. The gas flow system to be balanced may, alternatively, for example be a system for transporting and delivering nitrogen or carbon dioxide at different positions in for example a green house.

[0014] The gas flow system is provided with a plurality of, at least two gas flow inlets and/or outlets. In each outlet/inlet of the gas flow system there is a device, which may work like a valve or damper, which needs to be adjusted correctly to fulfil the gas flow requirements. [0015] The balancing unit used in the method may constitute a permanent part of the gas flow system when arranged as a valve or damper in a gas flow inlet/outlet. Alternatively, the balancing unit may be a temporary device replacing a system valve or damper during the balancing method, or be a temporary device connected to a permanent valve or damper of the gas flow system only during the balancing method.

[0016] The order in which the steps of the method are described above may be different. The step of supplying gas to the gas flow system may for example take place at an earlier point in the method than described above. For example after having arranged the balancing units at respective gas flow inlets/outlets.

[0017] For supplying gas to the gas flow system there may be arranged a fan connected to the gas flow system.

[0018] With this method it is possible, in a simple way and without losing precision, to adjust more complex gas flow systems, such as ventilation systems, where both easily replaced as well as larger devices, which are hard to temporarily replace, are used. If not all points in a gas flow system can be included in the balancing method, the end-result may be affected. There is for example risk of choosing the wrong reference if not all points in the gas flow system is included, which would lead to sub-optimal settings or imbalance, or, the non-included point affecting the rest of the system once one tries to adjust it, in a way that ruins the balance of the rest of the system.

[0019] All balancing units used in the method may comprise a transceiver and receiver and are wirelessly connected with the system controller during the balancing. The wireless transceiver may be used for transmitting condition parameters, e.g. pressure, flow, to a system controller or other balancing units wirelessly. The receiver may be used for receiving data wirelessly. The wireless connection could be of different technologies with different frequencies and protocols for example long range radio (Lora), Bluetooth mesh or Thread. A permanent valve/damper is typically not possible to (wirelessly) connect to the system controller without adding a balancing unit. In some embodiments the permanent valves do have a wireless connection available and comprise a motor and can be adjusted automatically. In this embodiment the permanent valve can be connected wirelessly to the system controller in order to include it in the balancing method. If the permanent valve uses another protocol for wireless communication than the system controller, a balancing unit might be connected to it instead.

[0020] The system controller is provided with a desired gas flow through each gas flow inlet/outlet. This desired gas flow may be provided manually by an operator to the system controller. Alternatively, the balancing unit may be pre-programmed with this information or data related to this information and sends this information to the system controller when connected to the system controller.

[0021] When the balancing units and/or the permanent valves or dampers are set in a first mode, this means that they all may be for example in a fully open position, or semi-open position. The first mode and the gas flow through a gas flow inlet/outlet could be different for different balancing units/permanent valves.

[0022] Based on the measured and desired gas flows, a condition parameter is determined/calculated for each gas flow inlet/outlet. The condition parameter may for example be a quotient between the measured gas flow and the desired gas flow.

[0023] A comparison is made of all calculated condition parameters, and a reference gas flow inlet/outlet is chosen among the gas flow inlets/outlets. The gas flow inlet/outlet for which there is a smallest quotient between the calculated and desired gas flow may for example be used as the reference.

[0024] As an example of choosing a reference based on smallest quotient, consider a simple gas flow system that comprises three gas flow inlets and every gas flow inlet has a desired gas flow of 10 litres per second. Once these are set in a first mode, for example fully open position, the gas flows through each inlet are calculated. If for example the calculated gas flow is 5, 10 and 15 litres per second for the first, second and third inlet respectively, the calculated quotient (calculated gas flow divided by desired gas flow) between calculated and desired airflow for the three inlets are 0.5, 1 and 1.5. The reference inlet in this example would then be the first inlet having a calculated quotient of 0.5 between calculated gas flow and desired gas flow, since it has the smallest quotient of the three inlets. [0025] The term reference gas flow inlet/outlet is here used for the gas flow inlet/outlet with which the other gas flow inlets/outlets are compared. In the field of air ventilation, this gas flow inlet/outlet may be known as the index inlet/outlet.

[0026] The gas flow through at least some of the gas flow inlets/outlets are adjusted one or more at a time until all gas flow inlets/outlets have been balanced. Sometimes a majority of or all the gas flow/inlets outlets are adjusted, except for the reference gas flow inlet/outlet, where adjustment of the gas flow is optional. Normally the reference inlet/outlet may be left in the first position, e.g. fully open, in order to minimize total pressure of the gas flow system. There can be occasions when the reference inlet/outlet must be adjusted from the first position, when for example there is a lower limit specified for the gas flow system of allowed pressure drop over each inlet/outlet. Sometimes some gas flow inlets/outlets are already in balance with the reference in its first position, why further adjustment of these is not necessary and these gas flow inlets/outlets not included in the balancing method. An already balanced gas flow inlet/outlet may have a condition parameter deviating for example with at most 20%, at most 15%, at most 10%, at most 5%, or at most 1% from the reference gas flow inlet/outlet condition parameter and is thereby considered balanced and not included in the balancing method.

[0027] The number of gas flow inlets/outlets that are adjusted at the same time may be one, two, three, or more. This may depend on how many inlets/outlets of a gas flow system that are included in the balancing method. More than one gas flow inlet/outlet may be adjusted at the same time but at different adjustment speeds, such that one at a time of the adjusted balancing units/permanent valves or dampers reaches it respective, second, balanced mode. Alternatively, the gas flow inlet/outlet are adjusted in sequence, such that one balancing unit/permanent valve or damper has reached its, second, balanced mode when starting the adjustment of the next gas flow inlet/outlet etc.

[0028] In methods wherein system balancing is based on measurements made at inlets/outlets only once during the balancing, erroneous adjustments of the devices at the inlets/outlets may be the results. This may for example be due to changes in surrounding conditions at the point in time the measurement was made. One might work around this problem if measuring at every inlet/outlet for a long time, but this makes the process laborious. Using the present method on the other hand, where the gas flows through the gas flow inlets/outlets are adjusted, one or more at a time, by re-calculating at least once the respective condition parameters and the condition parameter of the reference gas flow inlet/outlet, the result is a more reliably balanced gas flow system.

[0029] If striving for maximum energy efficiency, the reference should never be closed, but be fully open. It is, therefore, preferably, never closed/changed from its first mode. In some systems, however, there is a minimum requirement regarding pressure drop across the gas flow inlets/outlets, which means that one may need to adjust the reference from its first mode, i.e. adjust the gas flow through the reference gas flow inlet/outlet.

[0030] Furthermore, this method may find leaks in the gas flow system during the analysis of the system and act accordingly, e.g. exclude the affected control device from the balancing. Leakage is not possible to detect using a predictive balancing due to the assumption of conservation of mass, and thereby there is a risk of failing the balancing and that the balancing process needs to start over again. With a predictive balancing method, one tries to, based on acquired data of the system, calculate, or guess, the settings for the gas flow system that results in balance. There are several different predictive methodologies and the upside to using a predictive method is that it traditionally requires few adjustments and measurements, if it works. However, predictive balancing would only work properly if the gas flow system perfectly compares with drawing or ventilation plan and that the system does not leak which is often not the case. Using a predictive method is appealing compared to an iterative method, for example the traditional proportional method, when performing measurements and adjustments of inlets/outlets manually, since it is a laborious task. The traditional proportional method is meant to be completely iterative. Since manual adjustments, measurements and calculations are laborious, the operator must in practice perform some form of predictive balancing. Doing small enough adjustment steps for the method to be completely iterative would take the operator an unreasonable amount of time using traditional means. However, with the invention described, this can be done with minimal labour and using an enhanced iterative method will yield the most consistent and best results.

[0031] If calculating individual adjustment parameters and adjusting the settings of all airflow control devices at the same time, instead of adjusting one or a few at a time, one makes the system prone to errors due to anomalies, as it is difficult to monitor such events when making drastic changes to the entire system.

[0032] When a re-calculated condition parameter for a gas flow inlet/outlet is substantially the same as a re-calculated condition parameter of the reference gas flow inlet/outlet, that gas flow inlet/outlet is in a balanced mode. In this balanced mode the condition parameter of the adjusted gas flow inlet/outlet deviates from the re-calculated condition parameter of the reference gas flow inlet/outlet with no more than 20%, 15%, 10%, 5% or 1%. Once a gas flow inlet/outlet has been adjusted such that it has reached this balanced mode, a next gas flow inlet/outlet is adjusted.

[0033] As the condition parameter of the reference gas flow inlet/outlet is re-calculated this means that it may be (slightly) different when adjusting two subsequent gas flow inlets/outlets.

[0034] When all gas flow inlets/outlets have been adjusted, a condition parameter of any gas flow inlet/outlet may deviate from an average condition parameter of all gas flow inlets/outlets with at most 20%, or at most 15%, or most 10%, or at most 5%. Ideally, in the balanced mode, all condition parameters for any of the gas flow inlet/outlets are the same. In reality, if the system has not changed proportionally during the adjustment, the condition parameter may vary slightly between different gas flow inlets/outlets. A fine-tuning of the gas flow inlets/outlets may be performed to minimize such differences. The condition parameters of the different gas flow inlets/outlets of the final balanced gas flow system may deviate from an average condition parameter of all gas flow inlets/outlets with at most 20%, or at most 15%, or most 10%, or at most 5%, and may deviate more from the condition parameter of the reference gas flow inlet/outlet than during the individual adjustment of the respective gas flow inlet/outlet. This may be due to external disturbances, for example anomalies during the adjustment process, or disproportional behaviour, for example where sub-sets being present in the system which needs to be taken care of by an additional step in the balancing process, has affected the flow condition. By the final balanced gas flow system means a gas flow system where all gas flow inlets/outlets are fitted with valves or dampers according to the drawing or ventilation plan.

[0035] Before removing the balancing units, the gas supply can preferably be tuned to optimal settings via data from the system controller. Since there is not a requirement to have an exact amount of gas supply while performing the balancing, one might have set the gas supply such that it does not supply enough or too much gas, in order to achieve correct total flow in the system, a last adjustment of the gas supply might be needed. The system controller can calculate how the gas supply should be adjusted and instruct the operator to do so. Since the system is in balance the gas flow at each inlet/outlet will change proportionally. In one embodiment, the system controller is connected to the gas supply unit, e.g. a fan, and performs this adjustment automatically.

[0036] The balancing units used as valves/dampers in the gas flow inlets/outlets may comprises an adjustment mechanism arranged to adjust settings, e.g. gas flow, of the balancing unit automatically. If the balancing unit is arranged at a permanent valve adjustment of settings of the permanent valve/damper has to be made by an operator.

[0037] If the balancing unit is a temporary device, the settings of the temporary device may be translated to the permanent device after balancing has been performed and the permanent device replaces the temporary balancing unit in the balanced system.

[0038] The present balancing method utilizes a method similar to the traditional "proportional method" and enhances it with the strength that comes with real time monitoring of an entire gas flow system. With the present method there is a faster and more precise balancing process, than is known in the art.

[0039] With the present method the gas flow system can be balanced without the need of an operator to measure and manually adjust each device at every inlet/outlet several times and iteratively to reach satisfactory settings of the control devices controlling the gas flow. Traditional balancing method requires intense and laborious manual labour and a lot of experience in order to be carried out fast and to achieve optimal settings. In comparison to the traditional method, the balancing method described above is much simpler for the operator and provides much better working conditions.

[0040] An order of adjusting the gas flow through the gas flow inlets/outlets of the gas flow system may be based on how much the condition parameter for a gas flow inlet/outlet deviates from the condition parameter of the reference gas flow inlet/outlet when the balancing unit and/or the permanent valve is in the first mode.

[0041] The one or more gas flow inlets/outlets having a condition parameter deviating least from the condition parameter of the reference gas flow inlet/outlet may be adjusted first and so on. A gas flow inlet/outlet having a condition parameter deviating for example with at most 20%, or at most 15%, or at most 10%, or at most 5%, or at most 1% from the condition parameter of the reference gas flow inlet/outlet is considered balanced and may thereby not be included in the balancing method. [0042] When a balancing unit is arranged as a valve or damper in a gas flow inlet/outlet the system controller may be arranged to send instructions to the balancing unit to adjust a gas flow through the gas flow inlet/outlet until the second, balanced mode is reached.

[0043] The balancing unit may comprise an adjustment mechanism arranged to adjust gas flow through the gas flow inlet/outlet in which it is arranged as a valve/damper upon a signal from the system controller. The balancing unit may work as an automatic/smart valve/damper.

[0044] In this balanced mode, the condition parameter of the adjusted gas flow inlet/outlet deviates from the re-calculated condition parameter of the reference gas flow inlet/outlet with no more than 20%, 15%, 10%, 5% or 1%.

[0045] The method may be an iterative method, wherein while adjusting the gas flow through one or more of the gas flow inlets/outlets, gas flow may be continuously or repeatedly measured at the reference gas flow inlet/outlet and at said one or more of the gas flow inlets/outlets for which the gas flow is being adjusted and condition parameters re-calculated. [0046] Such re-calculation of condition parameters for gas flow inlets/outlets not being adjusted at the moment (and not being the reference inlet/outlet) may take place continuously or at regular intervals, such as every millisecond, every second, every other second etc., or for example be updated every time a gas flow inlet/outlet has been adjusted or adjusted to reach its, second, balanced mode. A reason for re-calculating/updating the condition parameters when in a balancing mode is that adjustment of individual balancing units/permanent valves or dampers may influence the gas flow at another gas flow inlet/outlet. The re-calculation of condition parameters may also change the order in which gas flow inlets/outlets are adjusted due to changes appearing in the system during the balancing method. This results in a so called enhanced proportional method, which is in traditional methodologies and with traditional instruments impractical to use, but is enabled via the method discussed above.

[0047] There are advantages with updating data from gas flow inlets/outlets that are not being adjusted. Most important, however, is that the data for the gas flow inlet/outlet that is being adjusted and the reference are re-calculated at least once, or continuously or at regular intervals, as discussed above.

[0048] The balancing unit arranged as a valve or damper in a gas flow inlet/outlet may be a temporary valve that during the method replaces a system valve or damper at the gas flow inlet/outlet of the gas flow system, and wherein, after adjustment of the balancing unit into a second, balanced mode, the balancing unit may be replaced by the system valve or damper of the gas flow inlet/outlet of the gas flow system, such that the gas flow through the inlet/outlet is substantially the same as when using the adjusted balancing unit.

[0049] That the gas flow through the inlet/outlet is substantially the same as when using the adjusted balancing unit is here meant that the gas flow does not differ with more than 20%, or 15%, or 10%, or 5% when measured according to the manufacturer's instructions. This calibration may involve a translation of settings for the adjusted balancing unit to the permanent valve/damper.

[0050] The balancing unit may be arranged to mimic the valve/damper it replaces during the balancing method. Since the gas flow system is being balanced and inlet/outlets being adjusted one or a few at a time, there is no need for the operator to input or calculate damper setting values to the system device. The balancing unit adjusts itself to optimal settings, balanced mode, which can directly translate to the permanent valve/damper. Thereby, the permanent valve/damper can be inserted without affecting the balance of the gas flow system. This means that the operator never has to re-calculate any k-factors (flow coefficient, often called k-factor) for the valve after adjusting it. Hence, no correction factor is needed to calculate the corresponding settings of the system valve/damper.

[0051] Since the balancing unit knows what permanent valve/damper it mimics, it also contains itself within the boundaries of that product. With mimicking is here meant e.g. measuring the flow in the same way and with the same characteristics as the permanent device being mimicked, resulting in no change in airflow when the translated setting is used and the permanent device is reinstated.

[0052] Contrary to only using information about the permanent valve/damper when calculating settings before one switches it back, the balancing unit or the system controller knows how much it is allowed to be opened or closed depending on the system valve/damper it mimics. If, on the other hand, the system only uses that information to translate the setting once in balance, the resulting setting will be at risk of being outside of the boundaries what the system valve/damper can or should, adjust to. If this error occurs at one inlet/outlet of the gas flow system, it risks ruining the balance of the entire system.

[0053] In an alternative method, the balancing unit is used as a permanent device in the gas flow system after completing the balancing method. [0054] The reference gas flow inlet/outlet may be identified as the gas flow inlet/outlet having the smallest quotient between the measured and desired gas flow or the reference gas flow inlet/outlet is a virtual gas flow inlet/outlet having a condition parameter being an average condition parameter of two or more of the gas flow inlets/outlets.

[0055] The number of gas flow inlets/outlets on which the condition parameter of the virtual reference gas flow inlet/outlet is based may be at least two, three or more, and may in some embodiments comprise all gas flow inlets/outlets included in the method. These would typically be selected from the first one, two, three, etc. in the adjustment order. How many inlets/outlets that are used in the virtual reference can depend on the size of gas flow system and/or the flow conditions near the reference inlets/outlets.

[0056] The reference may be chosen as the inlet/outlet with the smallest quotient between the measured and desired gas flow.

[0057] The method may further comprise a step of checking the reliability of the chosen reference gas flow inlet/outlet, comprising a) stopping or restricting the gas flow through all gas flow inlets/outlets except through the gas flow inlet/outlet being used as the reference; b) stopping or restricting the gas flow through the gas flow inlet/outlet being used as the reference, or c) changing gas supply to the gas flow system while monitoring the gas flow at one or more of the gas flow inlets/outlets, including the reference gas flow inlet/outlet.

[0058] In the method, the gas flow system may be monitored, i.e. gas flow and/or pressure drops may be monitored, to see how a) stopping or restricting the gas flow through all gas flow inlets/outlets except the gas flow inlet/outlet being used as the reference; b) stopping or restricting the gas airflow through the gas flow inlet/outlet being used as the reference, or c) changing gas supply to the gas flow system, affects the rest of the gas flow system, how the gas flow at the gas flow inlet/outlet used as the reference inlet/outlet is affected, and how the rest of the system is affected.

[0059] By changing gas supply to the gas flow system is meant that instead of opening / closing some gas flow inlets/outlets while monitoring the reference, the speed/rate of the fan/gas supply is changed and how it affects the conditions at the reference is monitored to assess whether it is "reliable" or not.

[0060] By such monitoring faulty construction may be identified, e.g. that pipes/ducts do not fit together properly so that there is leakage at a gas flow inlet/outlet, or that a system is incorrectly dimensioned. [0061] The choice of reference gas flow inlet/outlet affects the entire adjustment of every gas flow inlet/outlet, and it is very important that this is chosen correctly. If one choses the reference solely based on the smallest quotient between measured and desired gas flow, without continuous monitoring etc., one may risk choosing a "faulty" reference. For example, the conduit connecting the reference with the rest of the gas flow system might be leaking, which will lead to the flow not increasing properly at the reference when adjusting the rest of the system. This may lead to the system being excessively closed, costing energy and potentially causing other problems such as noise.

[0062] This reliability check may be performed at one or more occasions in the method described above. The reliability check may also be performed at different steps in the method. The reliability check also saves time, increases accuracy and helps the operator to identify faulty designs and constructions within the system. It also leads to more optimal settings, reducing the energy consumption of the system.

[0063] The reliability check may for example take place in the method when identifying a reference or after having identified the reference but before performing adjustment of the gas flow through the inlets/outlets.

[0064] It has not previously been known how to perform such reliability checks in a feasible manner. Due to the connection of all airflow control devices with the system controller in the present method, this reliability check is made possible. Thereby, a better result of the ventilation system balancing in the form of lower system pressure (less noise and lower energy consumption) and higher precision is possible.

[0065] The method may further comprise detecting an anomaly in the gas flow system during the balancing method by registering any change of gas flow through a gas flow inlet/outlet occurring without a) any adjustment of that gas flow inlet/outlet, or b) any adjustment of gas supply to the gas flow system.

[0066] While performing the balancing method anomalies may occur, which could affect the final result of the balancing. The change may be a rapid, unprovoked change etc. Anomalies might be due to for example someone opening a door or a window close to an inlet/outlet of the gas flow system, affecting the flow at that inlet/outlet and, therefore, also disrupting the entire conditions of the gas flow system. If this happens in the middle of the balancing method, it could mean that the final results differ a lot from the optimal settings. These events are very hard to detect by traditional means, since one usually measures at only one or two points in the gas flow system at a time, making the method very prone to such errors. Since one usually measures a short period of time for every adjustment and at only one point at the time in the entire system, it is virtually impossible to account for these events.

[0067] In the present method, since there is a continuous monitoring and analysing of gas flow in the system it can easily be detected when anomalies occur. If there is a rapid change of gas flow in one gas flow inlet/outlet without the others adjusting, the system knows something has changed, which should not have. The balancing method can then be stopped until the conditions go back to normal, or warn the operator that an anomaly has been detected, thus achieving better results and saving the operator additional time.

[0068] Due to the automatic detection and handling of anomalies, the balancing procedure will get much better results compared to the manual traditional method.

[0069] When the gas flow system has been balanced, the balanced balancing units may be used to simulate different conditions in the building in which the balanced gas flow system is installed.

[0070] Once the balancing units have been used to balance the system according to the design requirements, they can be easily used to simulate different conditions. For example, they could simulate, mimic, and help validate fire settings, making sure the system works as intended during a fire. They could also quickly simulate different forced conditions, e.g. when someone cooks food and starts their extra kitchen fan and validate that the system works as intended. Traditionally this is a very hard and laborious task. It may, for example, be that the central fan increases considerably in speed in order to achieve a high system pressure, which should lead to flue gas not being able to travel from one apartment to another via the ventilation. The speed the fan should reach is theoretically calculated, but it is very difficult to verify that the pressure you want is actually reached at all points in the ventilation system. With the help of the balancing units, this becomes much easier to verify.

[0071] The method may comprise an additional step, after having compared all calculated condition parameters and identified a reference gas flow inlet/outlet, of comparing a total gas flow through all gas flow inlets/outlets with a total desired gas flow through all the gas flow inlets/outlets, wherein if the total gas flow differs more than a predetermined value from the total desired gas flow, gas flow supplied to the gas flow system is adjusted until the total gas flow differs from the desired total gas flow with less than said predetermined value. [0072] A fan provides the gas flow to the gas flow system. The fan may be connected to the system controller, such that the system controller controls the gas flow supplied from the fan to the gas flow system.

[0073] The gas flow supply may be adjusted if the total gas flow through all gas flow inlets/outlets is determined to deviate by more than a predetermined value from a total desired gas flow. Alternatively, the system controller instructs an operator to change the gas supply from the fan to the gas flow system. This predetermined value is typically a difference in gas flow of 30% or more, or 20% or more, or 10% or more.

[0074] A total gas flow is here the sum of all measured gas flows or desired gas flows, respectively, through the gas flow inlets/outlets used in the method.

[0075] The method may further comprise an additional step, after having compared all calculated condition parameters and identified a reference gas flow inlet/outlet, of identifying any outlier gas flow inlet/outlet, wherein the condition parameter of an outlier gas flow inlet/outlet differs from the condition parameter of the reference gas flow inlet/outlet with more than a predetermined value, wherein for any identified outlier gas flow inlet/outlet, the gas flow there through is adjusted by changing the balancing unit and/or permanent valve from the first mode into an adjusted first mode, in which the condition parameter of the gas flow inlet/outlet differs from the condition parameter of the reference gas flow inlet/outlet with less than said predetermined value.

[0076] In this method an imbalance between different gas flow inlets/outlets may be identified and a pre-balancing takes place before the adjustment of the gas flow inlets/outlets according to the main method described above starts.

[0077] In the system controller, outlier gas flow inlets/outlets are identified.

[0078] A predetermined value could be a difference in condition parameter of more than a set value, for example 0.6 or more if the condition parameter is a quotient between the measured and desired gas flow, between the outlier gas flow inlet/outlet and reference gas flow inlet/outlet.

[0079] An operator may be asked by the system controller to adjust gas flow through the gas flow inlets/outlets (such as a permanent valve). Alternatively, the system controller sends instructions to the balancing unit to adjust the gas flow through a gas flow inlet/outlet.

[0080] With this method any large imbalances between the gas flow inlets/outlets may be identified and remedied through a first "rough" adjustment of the gas flows through the gas flow inlets/outlets or by adjusting the gas flow of the gas supplied to the gas flow system. This will result in a more controlled gas flow system, which is more likely to change in a proportional manner during the adjustment. Thereafter, the basic method as described earlier can be continued, i.e. to adjust the gas flow through all gas flow inlets/outlets while recalculating condition parameters.

[0081] The method may further comprise to identify among the gas flow inlets/outlets of the gas flow system arranged with a respective balancing unit, a sub-set of adjusted gas flow inlets/outlets, which sub-set of adjusted gas flow inlets/outlets after adjustment, while adjusting other non-adjusted gas flow inlets/outlets, no longer have a condition parameter substantially the same as the condition parameter of the reference gas flow inlet/outlet, and to a) re-adjust the gas flow inlets/outlets of each of the gas flow inlets/outlets of the identified sub-set of gas flow inlets/outlets, until each condition parameter is substantially the same as the condition parameter of the reference gas flow inlet/outlet, or b) identify a local reference among the sub-set of gas flow inlets/outlets and re-adjust each gas flow inlet/outlet of the identified sub-set of gas flow inlets/outlets, until each condition parameter is substantially the same as the condition parameter of the local reference gas flow inlet/outlet, and thereafter adjust the sub-set of gas flow inlets/outlets to the reference gas flow inlet/outlet.

[0082] Sub-sets of gas flow inlets/outlets that do not behave proportional during the balancing procedure may be due to the presence of branches in the gas flow system. In a branch, the gas flow inlets/outlets mostly influence each other (and not other parts of the gas flow system).

[0083] In some gas flow systems, these sub-sets are inherent to a permanent "master" valve. In such case, the entire sub-set can be balanced separately without taking into account the rest of the gas flow system. In the above described method there is, however, no such master valve or the master valve is provided with a balancing unit and included in the balancing system. The local reference may be identified in the same way as a reference is identified in the base method described above.

[0084] The last step in b) of adjusting the sub-set of gas flow inlets/outlets to the reference gas flow inlet/outlet (of the base method) is here meant that the inlets/outlets in the sub-set are adjusted until the condition parameters of the inlet/outlet of the sub-set are substantially the same as the condition parameter of the reference inlet/outlet, i.e. deviates from the condition parameter of the reference gas flow inlet/outlet with no more than 20%, 15%, 10%, 5% or 1%.

[0085] When a balancing unit is arranged at a permanent valve/damper in a gas flow inlet/outlet, the system controller may be arranged to send instructions to an operator, requesting manual adjustment of the gas flow through the permanent valve/damper until the second, balanced mode is reached.

[0086] The balancing units used connected to permanent valves/dampers of the system may be the same type of balancing unit as used as valve/damper in a gas flow inlet/outlet. Alternatively, the balancing unit connected to a permanent valve/damper may only comprise the gas flow measuring device and no adjustment mechanism, as the adjustment mechanism is not usable here. All the benefits of balancing unit is achieved (e.g. re-calculation of condition parameters, anomalies detection, automatic decision of order of adjustment, identification of reference etc.) except for the automatic adjustment, which has to be carried out by the operator.

[0087] According to a second aspect there is provided a balancing arrangement for balancing a gas system comprising a plurality of gas flow inlets and/or outlets, wherein the balancing arrangement comprises: a plurality of balancing units configured to be arranged as a valve or damper at a respective gas flow inlet/outlet and/or at a permanent valve or damper in a gas flow inlet/outlet of the gas flow system, wherein each balancing unit comprises a gas flow measuring unit for measuring a gas flow through a respective gas flow inlet/outlet. A system controller is wirelessly connectable to each balancing unit, wherein the system controller is arranged to receive a desired gas flow for each gas flow inlet/outlet and a measured gas flow through each gas flow inlet/outlet, the system controller further being arranged to, for each gas flow inlet/outlet, calculate a condition parameter based on the measured gas flows and desired gas flows, and to compare the calculated condition parameters for all gas flow inlets/outlets and based on the comparison, identifying a reference gas flow inlet/outlet; the system controller further being arranged to, based on calculated condition parameters send instructions to a balancing unit arranged as a valve or damper at a gas flow inlet/outlet to adjust a gas flow through the gas flow inlet/outlet or send instructions to an operator to manually adjust a gas flow through a permanent valve or damper. [0088] The balancing unit configured to be arranged as a valve or damper at a gas flow inlet/outlet may comprise an adjustment mechanism arranged to (automatically) adjust a gas flow through the gas flow inlet/outlet.

[0089] The balancing unit comprises an adjustment mechanism arranged to adjust gas flow through the gas flow inlet/outlet in which it is arranged as a valve/damper upon a signal from the system controller. The balancing unit works as an automatic/smart valve/damper.

[0090] The balancing unit may comprise a housing, a fixation mechanism for fixing the balancing unit as a valve or damper in a gas flow inlet/outlet. The balancing unit comprising an opening in the housing through which gas in the gas flow system is allowed to flow into/out from the gas flow inlet/outlet, an adjustment mechanism arranged to adjust a diameter of the opening in the housing such that the opening is adjustable between a fully open stage and a fully closed stage, and a gas flow measuring unit arranged to measure a gas flow through the opening. The gas flow measuring unit may comprise a pressure sensor arranged to measure an average differential gas pressure at the balancing unit opening.

[0091] The pressure sensor may be arranged along at least a portion of a perimeter of the opening in the housing of the balancing unit, the pressure sensor comprises at least two openings wherein a normal of an opening area is orthogonal to the flow direction through the opening in the housing.

[0092] The pressure sensor may comprise a hose arranged along the perimeter of the opening in the housing. The pressure sensor may be integrated in the wall of the perimeter of the housing. The at least two holes may have any shape and size. The at least two holes may be arranged substantially diametrically from each other across the opening in the housing.

[0093] The balancing unit may comprise a transceiver/receiver for wireless communication with the system controller.

[0094] The fixation mechanism may comprise two or more springs arranged on the housing with a direction of extension essentially radial to a direction of gas flow through the opening in the housing.

[0095] The system described above may comprise the balancing unit discussed here. The balancing unit and the fixation mechanism is constructed in such a way that it can be fixated in multiple different types and sizes of gas flow inlets/outlets. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Fig. 1 shows schematically a method for balancing a gas flow system.

[0097] Fig. 2 shows schematically a balancing arrangement for balancing a gas flow system. [0098] Figs 3a-3c show a balancing unit, isometric view, front view and side view, respectively, for use in the method illustrated in Fig. 1 and the arrangement shown in Fig. 2. Fig. 3d shows a gas flow measuring unit of the balancing unit.

DETAILED DESCRIPTION

[0099] Every time a building is being constructed or renovated the ventilation system may need to be balanced. Usually, a ventilation system comprises many gas flow outlets and inlets. In each outlet/inlet there is a product (device which works like a valve) which needs to be adjusted correctly to fulfil the ventilation requirements.

[00100] Below is described a method and arrangement for balancing a gas flow system in a more robust way than with existing methods and arrangements. Below is also described a balancing unit for use in the balancing arrangement and balancing method. The gas flow system to be balanced is not limited to ventilation systems, but the method and arrangement may also be useful for example for balancing systems for transporting and delivering nitrogen or carbon dioxide at different positions in for example a green house.

[00101] Fig. 2 shows schematically a balancing arrangement 1 for balancing a gas flow system comprising a plurality of gas flow inlets and/or outlets 2 (arrows indicating direction of flow). In Fig. 1 is schematically illustrated a method for balancing such a gas flow system. [00102] In each outlet/inlet 2 of the gas flow system there is a device, which may work like a valve or damper, which needs to be adjusted correctly to fulfil the gas flow requirements. The balancing arrangement 1 comprises a plurality of balancing units 10. The balancing units 10 are arranged 100 at a respective of the gas flow inlets/outlets of the gas flow system. When balancing the gas flow system, not all of the gas flow inlets and/or outlets may be included in the balancing. In some balancing procedures, only a sub-set of gas flow inlets/outlets may be included. Thereby, in some balancing procedures only gas flow inlets are included, in other balancing procedures only gas flow outlets are included, and in some balancing procedures both gas flow inlets and outlets are included in the balancing procedure. [00103] The balancing unit 10 used in the method/arrangement may constitute a permanent part of the gas flow system when arranged as a valve or damper in a gas flow inlet/outlet. Alternatively, the balancing unit 10 may be a temporary device replacing a system valve or damper during the balancing method. Thereafter, the temporary device is switched for the system valve/damper, wherein the system valve/damper is adjusted to have the same characteristics as the corresponding temporary device when put back in the gas flow system, such that the balanced gas flow at the gas flow inlet/outlet is kept. In yet an alternative, the balancing unit may be a temporary device connected to a permanent valve or damper of the gas flow system only during the balancing method. Thereafter, the balancing unit is disconnected from the permanent valve/damper and removed. The permanent valve/damper, could be a non-replaceable, usually large valve/damper of the gas flow system, which may not easily be temporary exchanged with a balancing unit. The balancing unit is then connected to the permanent valve or damper and used to measure a gas flow through the permanent valve/damper.

[00104] In Fig. 2, a gas flow system with six gas flow inlets/outlets 2 are illustrated. Each inlet/outlet provided with a balancing unit 10.

[00105] Each balancing unit 10 comprises a gas flow measuring unit 11 for measuring a gas flow through a respective gas flow inlet/outlet.

[00106] A system controller 20 is provided 101, to which each balancing unit 10 is wirelessly connected 102. For each gas flow inlet/outlet 2 provided with a balancing unit 10, a desired gas flow through said gas flow inlet/outlet is provided 103 to the system controller. This desired gas flow may be provided manually by an operator to the system controller 20. Alternatively, the balancing unit 10 may be pre-programmed with this information and sends this information to the system controller when connected to the system controller. The operator or balancing unit may possibly also send other information to the system controller, such as type of balancing unit or permeant valve/damper used at a specific inlet/outlet, location of the balancing unit/permanent valve or damper in the ventilation system, as well as boundary conditions, e.g. minimum allowed pressure drop over a device. The desired gas flow through each gas flow inlet/outlet for a specific building or part of a building may be determined by the building regulations.

[00107] Gas may be supplied 104 to the gas flow system 1 by means of a fan 40 connected to the gas flow system. Supplying gas to the gas flow system when performing the balancing method, lower than normal, normal gas flow conditions or maximal gas flow conditions for the system can be used. Only an approximately correct flow through the system is required for running the balancing method, as the balance is achieved by setting all balancing units proportionally. A higher flow than what is expected to be consumed at balance can be used, as well as a lower flow.

[00108] By means of the gas flow measuring device 11 of each balancing unit 10, a gas flow through each respective gas flow inlet/outlet is measured 105 when the balancing unit 10 and/or the permanent valve are set in a respective first mode. The system controller 20 is provided 106 through said wireless connection, with the measured gas flows.

[00109] When the balancing units 10 and/or the permanent valves or dampers are set in a first mode, this means that they all may be for example in a fully open position, or semiopen position. The first mode and the gas flow through a gas flow inlet/outlet could be different for different balancing units/permanent valves.

[00110] In the system controller 20, based on the measured gas flows and the desired gas flows, for each gas flow inlet/outlet a condition parameter is calculated 107. The condition parameter may for example be a quotient of the measured gas flow and the desired gas flow.

[00111] Thereafter, the calculated condition parameters for all gas flow inlets/outlets are compared 108 and based on the comparison, a reference gas flow inlet/outlet identified 109. The gas flow inlet/outlet 2 for which there is smallest quotient between the calculated and desired gas flow may for example be used as the reference.

[00112] The gas flow through at least some, a majority of or all gas flow inlets/outlets, except through the reference gas flow inlet/outlet where adjustment of the gas flow is optional, is adjusted 110 one or more at a time until all gas flow inlets/outlets have been balanced.

[00113] The number of gas flow inlets/outlets that are adjusted at the same time may be one, two or three of more. This may depend on how many inlets/outlets of a gas flow system that are included in the balancing method. More than one gas flow inlet/outlet may be adjusted at the same time but at different adjustment speeds, such that one at a time of the adjusted balancing units/permanent valves or dampers reaches it respective, second, balanced mode. Alternatively, the gas flow inlet/outlet are adjusted in sequence, such that one balancing unit/permanent valve or damper has reached its, second, balanced mode when starting the adjustment of the next gas flow inlet/outlet etc In some conditions, the first mode of the balancing unit/permanent valve can be considered to already be in balance and adjusting the valve or damper is unnecessary. This is for example the case if a gas flow inlet/outlet is situated very close to the reference inlet/outlet and the condition parameter is hence substantially the same as the reference. In this case, the first mode and the second balanced mode is the same.

[00114] An order of adjusting the gas flow through the gas flow inlets/outlets may be based on how much the condition parameter for a gas flow inlet/outlet deviates from the condition parameter of the reference gas flow inlet/outlet when the balancing unit and/or the permanent valve are set in the respective first mode. One or more gas flow inlets/outlets having a condition parameter deviating least from the condition parameter of the reference gas flow inlet/outlet may be adjusted first and so on.

[00115] During the adjustment of a gas flow inlet/outlet the condition parameter and the reference condition parameter are re-calculated at least once, such that the adjustment is not based only on the original condition parameters but on updated condition parameters. The condition parameters may be re-calculated, based on updated gas flow measurements, continuously or at regular intervals, such as every millisecond, every second, every other second etc., or for example be updated every time a gas flow inlet/outlet has been adjusted or adjusted to reach its, second, balanced mode. A reason for re-calculating/updating the condition parameters is that adjustment of individual balancing units/permanent valves or dampers may influence the gas flow at another gas flow inlet/outlet. Since the gas flow through one or a few gas flow inlets/outlets is adjusted at a time and re-calculated/updated condition parameters determined, the system behaves predictably and the method does not have to be looped over several times, and thus allowing an enhanced proportional method which is completely iterative and non-predictive.

[00116] During the adjustment 110, the respective condition parameter and the condition parameter of the reference gad flow inlet/outlet are re-calculated at least once. The adjustment 110 is performed by changing each balancing 10 unit and/or permanent valve from their respective first modes into a respective second, balanced mode, in which balanced mode the re-calculated condition parameter for a gas flow inlet/outlet is substantially the same as a re-calculated condition parameter of the reference gas flow inlet/outlet. The system controller 20 may be arranged to, based on the calculated condition parameters send instructions to a balancing unit 10 arranged as a valve or damper at a gas flow inlet/outlet 2 to adjust a gas flow through the gas flow inlet/outlet, or to send instructions to an operator to manually adjust a gas flow through a permanent valve or damper. [00117] In the balanced mode, the re-calculated condition parameter for a gas flow inlet/outlet is substantially the same as a re-calculated condition parameter of the reference gas flow inlet/outlet. This means that the condition parameter of the reference gas flow inlet/outlet may be (slightly) different when adjusting two subsequent gas flow inlets/outlets. [00118] When a re-calculated condition parameter for a gas flow inlet/outlet is substantially the same as a re-calculated condition parameter of the reference gas flow inlet/outlet, that gas flow inlet/outlet is in a balanced mode. In this balanced mode the condition parameter of the adjusted gas flow inlet/outlet deviates from the re-calculated condition parameter of the reference gas flow inlet/outlet with no more than 20%, 15%, 10%, 5% or 1%. Once a gas flow inlet/outlet has been adjusted such that it has reached this balanced mode, a next gas flow inlet/outlet is adjusted.

[00119] As the condition parameter of the reference gas flow inlet/outlet is recalculated this means that it may be (slightly) different when adjusting two subsequent gas flow inlets/outlets.

[00120] When all gas flow inlets/outlets have been adjusted, a condition parameter of a balanced gas flow inlet/outlet may deviate from an average condition parameter of all gas flow inlets/outlets with at most 20%, or at most 15%, or at most 10% or at most 5%. Ideally, in the balanced mode, all condition parameters for any of the gas flow inlet/outlets are the same. In reality, if the system has not changed proportionally during the adjustment, the condition parameter may vary slightly between different gas flow inlets/outlets. A fine-tuning of the gas flow inlets/outlets may be performed to minimize such differences. The condition parameters of the different gas flow inlets/outlets of the final balanced gas flow system may deviate from an average condition parameter of all gas flow inlets/outlets with at most 20%, or at most 15%, or most 10%, or at most 5%, and may deviate more from the condition parameter of the reference gas flow inlet/outlet than during the individual adjustment of the respective gas flow inlet/outlet. By the final balanced gas flow system means a gas flow system where all gas flow inlets/outlets are fitted with valves or dampers according to the drawing or ventilation plan.

[00121] The adjustment of the gas flow inlet/outlet may be performed by changing each balancing unit and/or permanent valve from their respective first modes into a respective second, balanced mode may be a stepwise adjustment or a continuous adjustment. Depending on how much a condition parameter differs from the condition parameter of the reference gas flow inlet/outlet, adjustment steps may be large or small. The method may be an iterative method, wherein, while adjusting 110 the gas flow through one or more of the gas flow inlets/outlets 2, gas flow is continuously or repeatedly measured at the reference gas flow inlet/outlet and at the one or more of the gas flow inlets/outlets for which the gas flow is being adjusted and condition parameters re-calculated.

[00122] The balancing units 10 used as valves/dampers in the gas flow inlets/outlets may comprise an adjustment mechanism 12 arranged to adjust settings of the balancing unit. Upon a signal from the system controller 10, the adjustment mechanism 12 may be arranged to adjust gas flow through the gas flow inlet/outlet in which it is arranged as a valve/damper. The balancing unit may works as an automatic/smart valve/damper.

[00123] The adjustment mechanism may use a motor, motor controller, microprocessor, gearing and an iris diaphragm, to control the gas flow though the gas flow inlet/outlet. The microprocessor may keep track of the current setting and send the appropriate signals to the motor controller to move the motor the desired amount. The motor controller may translate the microprocessor signals to appropriate power, or steps, to the motor. The motor rotates and with it the gearing, which moves the iris diaphragms mechanism, changing the orifice in which the air can flow.

[00124] The balancing units connected to permanent valves/dampers of the system may be the same type of balancing unit. Alternatively, the balancing unit connected to a permanent valve/damper may only comprise the gas flow sensing and a transceiver/receiver. As the adjustment mechanism is not necessary here, it may be removed/detached from the rest of the balancing unit. This may enable the operator to hook up the balancing unit at large permanent devices, which are not easily temporarily replaced. The operator can then tell the control system what product it is hooked up to, and all the benefits of the system is achieved except for the automatic adjustment, which then has to be carried out by the operator. The system controller informs the operator that a permanent valve/damper needs to be adjusted and when the balanced mode has been reached. The permanent valve does not have an adjustment mechanism arranged to automatically adjust settings of the permanent valve/damper, which has to be made by the operator.

[00125] The balancing unit 10 may be a temporary device that during the method replaces a system valve or damper at the gas flow inlet/outlet of the gas flow system. After adjustment of the balancing unit into a second, balanced mode, the balancing unit 10 may be replaced 111 by the system valve or damper of the gas flow inlet/outlet of the gas flow system, such that the gas flow through the inlet/outlet is substantially the same as when using the adjusted balancing unit.

[00126] The system controller 20 and the balancing units 10 may form a portable gas flow balancing arrangement 1, which may be moved between different buildings in which gas flow systems are to be balanced. It is, hence, reusable.

[00127] As an interface between the system controller and the operator, a webserver may be used. The webserver may be hosted by the system controller and may be connected via Wi-Fi on a regular smartphone. When connected to the webserver, the operator can monitor the balancing units and system controller and enter system parameters (e.g. desired flows, permanent valves/dampers, location of balancing unit) directly in the smartphone. The system controller could preferably be left in the building or somewhere close by within wireless range. The system controller could preferably be connected to the internet, which would make the webserver remotely accessible. In another embodiment, the interface between the system controller and the operator may be a remote server, where the system controller sends data via the internet to a regular web server and the user then enters via a website to monitor what happens.

[00128] The system controller 20 may be implemented as a virtual machine on a remote server. The system controller could be implemented on a remote server, which uses the internet to communicate with the balancing units. The remote system controller could host a webserver, which the operator can access via the internet by using for example a smart phone in order to interact with the system. In one embodiment, the physical system controller remains on site and is connected wirelessly to all the balancing units, but sends data to a remote server which hosts a web server, which the operator can access via the internet. The system controller 20 may be configured to communicate with and control the gas supply unit. [00129] Data from/used in the balancing method, such as used settings, balancing modes, gas flows and other data of interest, may be saved to a database in the system controller or in a server. This may later be used to automatically generate required documentation. The data could also be used to analyse the gas flow system.

[00130] The method described above may further comprise a step of checking the reliability 200 of the chosen reference gas flow inlet/outlet, comprising a) stopping or restricting the gas flow through all gas flow inlets/outlets except the gas flow inlet/outlet being used as the reference; b) stopping or restricting the gas flow through the gas flow inlet/outlet being used as the reference, or c) changing gas supply to the gas flow system, while monitoring the gas flow at one or more of the gas flow inlets/outlets, including the reference gas flow inlet/outlet.

[00131] In the method, the gas flow system may be monitored, i.e. gas flow and/or pressure drops may be monitored, to see how a) stopping or restricting the gas flow through all gas flow inlets/outlets except the gas flow inlet/outlet being used as the reference; b) stopping or restricting the gas airflow through the gas flow inlet/outlet being used as the reference, or c) change gas supply to the gas flow system, affects the rest of the gas flow system, how the gas flow at the gas flow inlet/outlet used as the reference inlet/outlet is affected, and how the rest of the system is affected.

[00132] The method may further comprise detecting 300 an anomaly in the gas flow system during the balancing method by registering any change of gas flow through a gas flow inlet/outlet occurring without a) any adjustment of that gas flow inlet/outlet, or b) any adjustment of the gas supply to the gas flow system.

[00133] While performing the balancing method anomalies may occur, which could affect the final result of the balancing. Anomalies might be due to for example someone opening a door or a window close to an inlet/outlet of the gas flow system, affecting the flow at that inlet/outlet and, therefore, also disrupting the entire conditions of the gas flow system. [00134] When the gas flow system has been balanced, the balanced balancing units may be used to simulate 400 different conditions in the building in which the balanced gas flow system is installed. Such conditions may for example be fire and forced airflow conditions.

[00135] The method may comprise an additional step, after having compared 108 all calculated condition parameters and identified 109 a reference gas flow inlet/outlet, of comparing 500 a total gas flow through all gas flow inlets/outlets with a total desired gas flow through all the gas flow inlets/outlets, wherein if the total gas flow differs more than a predetermined value from the total desired gas flow, gas flow supplied to the gas flow system is adjusted until the total gas flow differs from the desired total gas flow with less than said predetermined value. A total gas flow being the sum of all measured gas flows or desired gas flows, respectively, through the gas flow inlets/outlets used in the method. [00136] The method may further comprise an additional step, after having compared 108 all calculated condition parameters and identified 109 a reference gas flow inlet/outlet, of identifying 600 any outlier gas flow inlet/outlet, wherein the condition parameter of an outlier gas flow inlet/outlet differs from the condition parameter of the reference gas flow inlet/outlet with more than a predetermined value, wherein for any identified outlier gas flow inlet/outlet, the gas flow there through is adjusted by changing the balancing unit 10 and/or permanent valve from the first mode into an adjusted first mode, in which the condition parameter of the gas flow inlet/outlet differs from the condition parameter of the reference gas flow inlet/outlet with less than said predetermined value.

[00137] In this method an imbalance between different gas flow inlets/outlets may be identified and a pre-balancing takes place before the adjustment of the gas flow inlets/outlets according to the main method described above starts.

[00138] The method may further comprise to identify 700 among the gas flow inlets/outlets of the gas flow system arranged with a respective balancing unit 10, a sub-set 30 (Fig. 2) of adjusted gas flow inlets/outlets, which sub-set of adjusted gas flow inlets/outlets after adjustment, while adjusting other non-adjusted gas flow inlets/outlets, no longer have a condition parameter substantially the same as the condition parameter of the reference gas flow inlet/outlet, and to a) re-adjust the gas flow inlets/outlets of each of the gas flow inlets/outlets of the identified sub-set of gas flow inlets/outlets, until each condition parameter is substantially the same as the condition parameter of the reference gas flow inlet/outlet, or b) identify a local reference among the sub-set of gas flow inlets/outlets and re-adjust each gas flow inlet/outlet of the identified sub-set of gas flow inlets/outlets, until each condition parameter is substantially the same as the condition parameter of the local reference gas flow inlet/outlet, and thereafter adjust the sub-set of gas flow inlets/outlets to the reference gas flow inlet/outlet. Sub-sets of gas flow inlets/outlets that do not behave proportional during the balancing procedure may be due to the presence of branches in the gas flow system. In a branch, the gas flow inlets/outlets mostly influence each other (and not other parts of the gas flow system).

[00139] Sub-sets 30 of gas flow inlets/outlets that do not behave proportional during the balancing procedure may be due to the presence of branches in the gas flow system. In a branch, the gas flow inlets/outlets mostly influence each other (and not other parts of the gas flow system). [00140] Figs 3a-3c show a balancing unit 10, isometric view, front view and side view, respectively, for use in the method illustrated in Fig. 1 and the arrangement shown in Fig. 2.The balancing unit 10 comprises a housing 9, a fixation mechanism 13 for fixing the balancing unit 10 as a valve or damper in a gas flow inlet/outlet, an opening 14 in the housing 9 through which gas in the gas flow system is allowed to flow into/out from the gas flow inlet/outlet, an adjustment mechanism 12 arranged to adjust a diameter of the opening 14 in the housing 9 such that the opening is adjustable between a fully open stage and a fully closed stage, and a gas flow measuring unit 11 arranged to measure a gas flow through the opening 14.

[00141] The gas flow measuring unit 11 may comprises a pressure sensor arranged to measure an average differential gas pressure at the balancing unit opening 14. The pressure sensor may be arranged along at least a portion of a perimeter of the opening 14 in the housing 9 of the balancing unit 10. The pressure sensor may comprise at least two openings 16 wherein a normal of an opening area is orthogonal to the flow direction through the opening 14 in the housing 9. The gas flow measuring unit 11 may, see Fig. 3d, comprise a pressure sensor comprising a pressure hose 15 arranged along at least a portion of a perimeter of the opening 14 in the balancing unit 10, wherein the pressure hose 15 is provided with at two or more openings 16 for measuring an differential average gas pressure at the balancing unit 10. [00142] The gas flow measuring device 11 may be a pressure sensor, such as a thermal differential pressure sensor, a piezo resistive strain gauge differential pressure sensor, a capacitive differential pressure sensor, an electromagnetic differential pressure sensor etc. (measuring a pressure drop over the gas flow inlet/outlet), gas flow speed sensor using e.g. an ultrasonic sensor, a hot wire anemometer or a mechanical flow meter, or other device for measuring a gas flow.

[00143] The fixation mechanism may comprises two or more springs, see Figs 3a, 3b, arranged on the housing 9 with a direction of extension essentially radial to a direction of gas flow through the opening 14 in the housing.

[00144] The fixation mechanism maintains pressure against the inlets/outlets inner walls using the spring, and the spring is dimensioned in such a way that enough force is maintained in order to fixate the unit in several different sized inlet/outlets. Usually standardized sizes, e.g. 100mm, 125mm, of conduits and inlets/outlets are used in a ventilation system. [00145] The surface of the fixation mechanism that interacts with the inner walls of the inlet/outlet may be provided with a material with a high friction coefficient, e.g. rubber, in order to fixate the balancing unit.

[00146] Preventing leakage between the balancing unit and the duct system in which the balancing unit is installed is important, in order to avoid measurement errors of the gas flow, i.e. all the gas flow should pass through the opening in the housing of the balancing unit, where the measuring and adjusting of flow is performed. This may be achieved by having a gasket, or foam, as a gas seal, which prevents leakage between the mating surfaces of the duct and balancing unit. The gasket has to function with several standardized sizes of inlets/outlets.

[00147] In order to identify in which position the adjustment mechanism is, switches can be used. These switches can for example be placed so that the adjustment mechanism activates a switch when it is fully opened and another switch when it is fully closed. This enables the balancing unit to calibrate the position of the adjustment mechanism.

[00148] The adjustment mechanism may be adjusted by means of a stepping motor.

[00149] The opening in the housing of the balancing unit may comprise an iris diaphragm as the adjustment mechanism.

[00150] The opening where gas is supplied may be a central opening in the balancing unit. In the fully closed stage, there is minimal gas flow through the opening of the balancing unit. In the fully open stage, the diameter of the opening of the balancing unit may be substantially of the same size as the diameter of the gas flow inlet/outlet. Alternatively, the fully open stage may correlate to a diameter smaller than the opening of the gas flow inlet/outlet.

[00151] The adjustment mechanism may comprise an iris diaphragm. The adjustment mechanism may use a motor, motor controller, microprocessor, gearing and an iris diaphragm, to control the gas flow through the gas flow inlet/outlet. The microprocessor may keep track of the current setting and send the appropriate signals to the motor controller to move the motor the desired amount. The motor controller may translate the microprocessor signals to appropriate power, or steps, to the motor. The motor rotates and with it the gearing, which moves the iris diaphragms mechanism, changing the orifice/diameter of the opening in which the gas can flow. [00152] The gas flow measuring unit is arranged to measure a gas flow through the opening, hence, measures a gas flow through the gas flow inlet/outlet, wherein the diameter of the gas flow inlet/outlet is varied by means of the adjustment mechanism of the balancing unit.

[00153] The balancing unit may be used in the system or method described above.

[00154] The balancing unit may further comprise an energy source (such as a battery) and a processor (transmitter, receiver, microcontroller) for sending/receiving data/signals to a system controller. The balancing unit may be arranged to be wirelessly connectable to a system controller. The balancing unit may measure a gas flow and send information about this gas flow to the system controller. The balancing unit may receive a command from the system controller to adjust the diameter of its opening and may receive a command from the system controller as to how much the diameter of the opening should be adjusted. The fixation mechanism is adjustable such that the balancing unit may fit several standardized sizes of gas flow inlets/outlets.

[00155] A common way to measure pressure drop over a gas flow inlet/outlet is to have a single measuring point, consisting of a measuring nipple (basically a hole in the duct), where the measured pressure then is compared with the atmospheric pressure.

[00156] As the balancing unit described above often is connected to bends, T-crosses, etc. in ducts, an uneven, turbulent pressure may be obtained inside the balancing unit. If only measuring the pressure at one point (as traditionally performed), there is a risk of getting a rather misleading value as the pressure may fluctuate a lot along the balancing unit. Thereby, an average gas pressure will give the best/most accurate calculated gas flow.

Using a pressure hose with a number of openings distributed along the hose leads to a more stable pressure reading since it is most likely that a measuring point at e.g. a high-pressure area and a low-pressure area is obtained. This will automatically give an average value into the pressure sensor, as the mixed pressures in the hose will lead to an average value. Based on the measured pressure drop and current settings of the balancing unit, a flow coefficient for the balancing unit can be obtained. The flow coefficient, often called K-factor, may be obtained from a flow-coefficient curve, which gives a specific flow coefficient depending on the settings of the balancing unit. Based on this flow coefficient, gas flow at a balancing unit can be determined. When measuring a pressure drop over the balancing unit, the gas flow may be calculated through the formula q = k * sqrt (dp), where q is the flow, dp is the pressure drop and k is a constant that depends on the valve's position and design. In order to calculate the gas flow with this method, you therefore need to know the k-value of your valve for the current setting, in addition to the pressure drop. The K-values for valves are obtained through laboratory work in a test environment.