The present invention relates to a heating system for buildings, said system comprising a storage tank for a heating medium, preferably water, a heating means connected thereto, a plurality of radiators, and a pipeline system conveying the heating medium and extendin between the storage tank and the radiators.

Present-day heating systems for buildings, in which heated water is conveyed in a pipeline system from a boiler, hot-water heater or heat exchanger to a number of radiators in different parts of the building, in particular an apartment building, and in which use is made of a water storage tank, may be defined as a pressure system because of the static excess pressure developed by a column of water extending from an expan- sion vessel in the highest part of the system to the water storage tank. The construction of the water storage tank therefore is subject to safety regulations.

With the rapid increase in oil prices, so-called "indirect" electric heating, i.e. the heating of water by means of cartridge type heaters, has become an in¬ creasingly common alternative to oil firing. A change-over from oil firing to indirect electric heating implies that the fuel oil tank is scrapped and that an electric heating cartridge is mounted in the oil burner, or a heating cartridge with built-in water storage tank is installed. The fuel oil tank which, in itself, would be an excellent water storage tank, cannot be used as such because it does not satisfy standard speci¬ fications for pressure vessels.

The main object of the present invention is to provide a heating system which does not operate with a static excess pressure in the water storage tank, deriving from the water columns in the pipeline system, but uses a circulation pump to maintain the requisite

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pump pressure in the radiators and pipelines during operation.

A further object of this invention is to provide a heating system in which an existing fuel oil tank or the like can be used for the storage of water.

According to the invention, these objects are achieved by means of a heating system whose charac¬ teristic features will appear from the characterising clauses of the appended claims. The invention will be described in more detail below, reference being had to the accompanying drawings illustrating two embodiments of the invention. In the drawings:

Figs. 1 and 2 illustrate diagrammatically a first and a second embodiment of the heating system according, to the present invention.

A tank 1 (Figs. 1 and 2) of any suitable form can be used for the storage of water because the tank need not satisfy the standard specification for pressure vessels. The tank is connected by two schematically shown connections 14 to a heating means {not shown) , such as an electric heating cartridge, an oil burner, a wood burner, an open fireplace etc. The tank preferably is positioned at the very bottom of the building or in the same plane as the heating means. However, it is also possible to provide the heating means above the tank and vice versa.

The drawings also illustrate schematically a number of radiators 2 located in different parts of the building. Extending between the tank and the radiators are a pipeline 3 which conveys heated water to the radiators, and a pipeline 4 which conveys water from the radiators. Pipelines 5 connect the radiators 2 to the pipelines 3 and 4. Connected in the pipeline 3 are a pressure gage 11, a thermometer 10 and a circulation pump 9, said circulation pump being located below the water level

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in the tank. The function of these components is the same as in prior art heating systems, for which reason these components will not be described in detail.

A shunt line 6 connects the pipeline 4 with a shunt valve 8 which is connected in the pipeline 3 and by means of which it is possible to control, in known manner, the temperature of the water conveyed in the pipeline 3, by controlling the intake of heated water from the tank. A throttle valve 20 is connected in the pipeline

4 and is used upon filling of the heating system according to the invention, as will be described in more detali below.

A hot-water heater 16 is suspended from the roof of the tank or mounted therein in some other suitable manner. A tap line 17 extends from the hot-water heater to different tapping points in the building. The hot-water heater is connected to an incoming cold-water line 22 via a valve pipe 21 comprising non-return, vacuum and safety valves. When hot water is tapped from the hot-water heater, the valve pipe 21 senses the pressure reduction in the heater and gradually replenishes the cold-water volume via the cold-water line 22. A tempera¬ ture limiter 23 in the line 17 is connected, via a line 24, to the valve pipe 21.

A filling line 19 extends between the pipeline 4 and the cold-water line 22, and a filling valve 7 is connected in the filling line for filling water into the tank 1, the pipelines 3, 4 and the radiators 2.

It should be pointed out that the tank also com¬ prises means (not shown) in its lower part for draining the tank.

The essential feature of the invention resides in that the pipeline system is closed and without com¬ munication with the surroundings during operation. The pipeline system comprises a valve which is adapted

to vent the system of air when the system is filled with water. The pipeline system being vented of air and closed, the water in the system, because of the siphon principle, will not produce any static excess pressure within the tank. Consequently, the tank cannot be regarded as a pressure vessel and therefore need not satisfy the standard specifications for such vessels. In Fig. 1, the valve 13 is self-controlled and combined with a balance vessel 12. In this embodiment, the valve is disposed in the uppermost part of the heating system, and the balance vessel is connected to the pipeline 3. The valve acts as a non-return valve and is adapted to vent the radiators 2 and the pipelines 3, 4, 5 of air when the heating system is filled with water, and to prevent air from entering the pipeline 3. The valve is so adjusted that it does not let out any water which, during normal operation, is circulated in the pipelines and the radiators. At excess pressure, the valve 13 acts as a safety valve and lets out water from the balance vessel 12 which is adapted to take up the slight lowering of the water level which occurs when the pipelines and the radiators are filled with water and connected to the tank, as will be described in detail below. A double-bent pipe 15 connects the interior of the tank 1 with the surroundings and acts as a safety valve against excess pressure within the tank. To pre¬ vent evaporation from the tank, the pipe 15 is partly filled with water. The function of the heating system according to the invention and an arrangement where the tank remains unaffected by any static excess pressure from water columns in the pipeline system will appear from the following description of the water-filling operation. in the embodiment shown in Fig. 1, the system is filled with water in the following manner. The valves 7, 8 and 20 are opened, and the tank 1 is filled via

the line 22 up to the level 18. The valve 20 is then closed, and the shunt valve 8 is so adjusted that the ^' water can flow only upwardly in the pipeline 3. The pipelines 3, 4 are now filled in parallel with water, and the water continues upwardly via the radiators 2 and the balance vessel 12 to the valve 13. The air in the pipelines, the radiators and the balance vessel is pressed out through the valve 13, and filling is interrupted by closing the valve 7 when water begins to escape through the valve 13. The valve 20 is opened, and the shunt valve 8 is. so controlled that a free passage is obtained from the pipeline 3 both to the shunt line 6 and directly to the tank 1. The level in the balance vessel is slightly lowered until balance has been established. The pressure gage 11 now indicates that the pressure within the pipeline 3 is zero.

The valve 20 is slightly throttled during operation, The circulation pump 9 then increases the pump pressure in the pipeline 3 and in the radiators, whereby the water is prevented from becoming thinner and forming steam at high temperatures.

Fig. 2 shows another embodiment in which the air-venting valve which in Fig. 2 is designated 13', has been placed in the pipeline 3 adjacent to the tank 1. The valve 13" is opened and closed manually. In all other respects, the embodiments shown in Figs. 1 and 2 are identical.

The system shown in Fig. 2 is filled in the fol¬ lowing manner. The tank 1 is filled up to the level 18 in the manner described in connection with Fig. 1, whereupon the valves 20 and 8 are closed and the venting valve 13* is opened so that the water can flow upwardly within the pipeline 4 and press out the air in the pipelines 3, 4 and the radiators 2 through the valve 13'. When water begins to escape through the valve 13', this valve is closed, and the valve 7, 8 and 20 can now be opened and the circulation pump 9 can be

started.

Considerable advantages are obtained by using a tank which need not satisfy the standard specifica¬ tions for pressure vessels. Thus, the space required for such a tank is less than the space taken up by a pressure vessel, and furthermore the tank can be produced at far lower cost than the pressure vessel.