Background of the invention The present invention relates to a heat recovery device incorporated in a drain siphon, said siphon comprising an inlet and an outlet, said heat recovery device is of the liq- uid-liquid heat exchanger type having a primary liquid circuit arranged inside the drain siphon device, said primary liquid circuit being interposed between a water supply source and a water outlet device.

On an everyday basis, households and industry alike discharge huge amounts of warm or hot water into the drains. This add up to an enormous amount of unused energy being discharged into the drainage/sewage systems around the world. Usually, hot water discharge from industrial use, dishwashers, kitchen sinks, showers and the like is led directly into the drains without a substantial drop of temperature in the water.

The accumulated heat in the water is therefore not exploited completely before it is led out into the drains. Water has a very high thermal capacity, which is to say that water is able to accumulate a lot of joules/cm3 in comparison to other materials.

Document EP-A-492031 describes a heat recuperation device for sanitary installa- tions. The device comprises a heat exchanger arranged between a floor drain and a drainage system having an interior liquid circuit connected to a main supply whereby, when the drainage water is led through the heat exchanger, heat will be exchanged from the waste water to the cold use water thus preheating the use water. The ar- rangement of the heat exchanger is complicated in that the warm water from the drain is pumped into the heat exchanger and after going through the heat exchanger is led back into the drains. The use water is pumped in a separate circuit into said heat ex- changer for exchanging of energy with the waste water. This device, although appar- ently being effective, is expensive to install and furthermore requires that substantial constructional changes be made to the surroundings of the drain.

Another heat recovery device is known from US-A-5791401 wherein a heat recovery device is disclosed which consists of a system wherein the cold water supply to a

shower installation is wound around a part of the drain installation. This system is very cheap to install as it only require part of the water supply line being wound around the waste water pipe, i. e. the drain. However, the energy recovery from this kind of device is very low and the effect on preheating the use water for the shower installation is quite minimal.

The object of the present invention is therefore to provide a simple and cheap heat recovery device which can reuse some of the energy accumulated in warm or hot waste water for preheating of fresh water before the waste water is drained out into the draining system.

According to the invention this object is achieved by a device distinguished in that the device comprises a shut-off arrangement comprising a first ball valve which ball valve is connected to a floating device arranged inside the drain siphon. With this system warm or hot waste water led into the siphon is not wasted but the energy accumulated in the water is at least partially recovered before discharging the waste water by the liquid heat recovery device installed inside the system. The preheating of the cold water supply is thereby optimised and the overall energy demand in the system is re- duced.

The device according to the invention works in the following manner: When the si- phon is empty, the floating device with its attached first ball valve will be in the bot- tom most position, whereby the first ball valve will shut off the outlet of the siphon to the drainage system. Hereby is assured that odour will not come up through the drain pipe. As warm or hot waste water is led into the siphon, the water level inside the si- phon will rise. As the water level inside the siphon rises, it will eventually reach the level where the floating device connected to the first ball valve will be caused to float whereby the first ball valve will be dislodged from its valve seat in the bottom of the siphon and thereby letting waste water into the drain. Before the waste water is led out of the siphon, it will have exchanged part of its accumulated heat energy to the pri- mary liquid circuit wherein the cold use water from the mains is circulated inside the siphon before being led to a water outlet device. As the water level in the siphon

drops, the floating device will drop and the first ball valve will settle back in the valve seat and thereby shutting off the outlet from the siphon. The siphon will at this point still be filled with warm water which will exchange its accumulated energy with the primary liquid circuit and thereby preheat the cold water supply. As long as the float- ing device is not elevating the first ball valve from the valve seat at the bottom of the siphon there will be a water lock sealing off the sewage system from the space above the siphon.

In a further advantageous embodiment of the invention a second ball valve is arranged below the first ball valve. This second ball valve is a security device arranged in the drain system such that should over-pressure or flooding occur elsewhere in the sewerage system, for example due to excessive rains or an explosion in the sewage system, the ball valve will effectively shut off access to the siphon, whereby flooding of water stored in the siphon into the space above the siphon device is avoided.

In a further embodiment where the two balls in the first and second ball valves are equipped with magnetic means inside the balls such that when the first ball valve de- vice is in its shut position, i. e. the first ball is in the valve seat, this ball due to its mag- netic characteristics will attract the second ball in the second ball valve means to an upper closed position. Hereby is assured that should over-pressure or excessive flooding in the sewage system suddenly occur, the safety device of the second ball valve is already in place and no flooding or over-pressure will be transferred from the sewage system into the siphon device.

When waste water is led into the siphon device a flow of water will occur through the drain of the siphon whereby the second ball in the second ball valve device will be forced downwards due to the water passing by the ball. In order to avoid that the sec- ond ball valve is closed due to this water pressure, distance keeping means are ar- ranged on the underside of the second ball valve. Hereby is assured that the second ball valve will never block the outlet from the siphon device in a downward direction due to water flowing from above.

It is foreseen that the heat recovery device can be installed below wash basins or in shower drains, but it can also be installed in larger installation where more sources of hot or warm waste water can be led through one common heat exchanging device. In this case the siphon is equipped with more inlet openings and the outlet opening from the siphon device is correspondingly dimensioned to be able to accommodate a larger flow of waste water.

In a further advantageous use of the system it can be built into premanufactured shower bottoms. It is quite normal that when renovating older houses people will re- place bath tubs with shower cubicles. By arranging this heat recovery device in the shower bottom, which anyway will have to be elevated from the normal floor because of the space required by a water lock, it will not require any constructional work to install a heat recovering device according to the invention as it is preinstalled in the shower bottom.

The principle of the invention is scaleable, which means that it will be able to recover wasted energy from small drains, i. e. from kitchen sinks and wash basins and the like.

In this case the siphon's volume should be 5 to 10 litres. However, for bigger installa- tions, for example when renovating or building new apartment blocks or in industries having a big usage of wann or hot water, the siphon's volume can be increased up to about 100,000 litres.

In a further advantageous embodiment all surfaces of the device is coated with a fric- tion reducing and/or non-stick surface coating, for example a Teflon. By coating all surfaces with this kind of coating, the requirements for maintenance are greatly re- duced in that waste material suspended in the hot or warm waste water will not get stuck in the siphon and thereby isolate the heat exchange process between the waste water and the primary liquid circuit. Furthermore, when they are non-stick or friction reduction treated, the waste material suspended in the water will not get stuck in the siphon and thereby block the valve seats or the drain outlet and thereby render the de- vice not functioning.

The heat recovery device according to the invention can be manufactured from any suitable material. In preferred embodiments the heat recovery device is manufactured from for example stainless steel, ordinary steel, plastics, modified polymers, glass, ceramics, nylons, glass fibres, resin or resin based fibre reinforced materials or copper.

The heat recovery device can advantageously be manufactured by a combination of these materials. The ball valves for example can advantageously be manufactured from plastics, stainless steel or ceramics, where the housing of the siphons is advanta- geously made from plastics or stainless steel. In some applications the primary liquid circuit can advantageously be manufactured from copper as copper tube is easy to bend and furthermore has good heat exchanging capabilities.

The heat recovery device according to the invention can have any shape, but in a pre- ferred embodiment it is of a circular or oval shape and the primary liquid circuit is a wound spiral inside the siphon conforming to the outer shape of the siphon itself.

The magnetic means arranged inside the first and second ball valve means are dimen- sioned so that the magnetic force will be sufficient for the two balls to attract each other through the distance between the first and second ball valve seats. The magnetic means can advantageously be arranged inside the ball valve means in such a way that the distance and thereby the influence of the magnetic forces can be adjusted, for ex- ample by arranging the magnetic means with a thread such that a screw member can be screwed into said magnetic means and by turning the screw one or the other way the distance between the two magnetic means can be adjusted.

In a further advantageous embodiment of the invention a secondary liquid circuit can be arranged inside the siphon and inside the first primary liquid circuit. This secondary liquid circuit can be connected to a heat accumulation device, for example in the shape of a general heating installation for heating of houses or rooms in houses.

Description of the drawing Further advantages and characteristics of the device according to the invention will become clear from the following detailed description provided purely by way of non- limiting example with reference to the appended drawing, in which fig. 1 is a vertical cross section of a device according to the invention.

With reference to the drawing a heat recovering device, generally indicated by 1, is illustrated mounted in a floor drain 10. The heat recovery device 1 is in this example a cylindrical member 3 inside of which is arranged a primary liquid circuit 2. A drain 4 is arranged at the bottom of the heat recovery member as an integral part of the cylin- drical member 3. Inside the cylindrical member is arranged a shut-off device 5 com- prising a floating device 6 and a first ball valve 7. The floating device 6 and the first ball valve 7 are connected by a member 8.

The primary liquid circuit 2 arranged inside the heat recovery member 1 is connected to a fresh water supply 9, in this example at the bottom of the heat recovery device, but the fresh water supply inlet could just as well be arranged elsewhere in the device.

The preheated fresh water outlet 11 is arranged at the opposite end of the primary liq- uid circuit 2, in this example in the shape of a heat exchanging spiral inside the device.

A second ball valve 12 is arranged below the first ball valve 7. The second ball valve seat 13 is arranged at the upper part of the ball valve housing 14. Inside the first ball valve 7 and the second ball valve 12 are arranged magnetic means 15. The magnetic means arranged inside the ball valve means are dimensioned so that the magnetic in- fluences can attract the two balls to each other and overcome the distance between the two valve seats 13 and 17. Below the second ball valve 12 on the side of the ball valve housing 14 are arranged distance keeping means 19.

The heat recovery device functions so that when hot waste water is led into the floor drain 10 and into the heat recovery device 1, the first ball valve 7 is resting on the valve seat 17, whereby access to the drain 4 is closed. As the waste water inside the

heat recovery device rises, the waste water will exchange energy with the fresh water circulating in the primary liquid circuit 2. As the waste water level inside the device keeps rising, it will eventually rise up to a level where the floating device 6 will be activated and will rise together with the increased water level. As the floating device 6 rises the connecting member 8 will cause the ball valve 7 to be elevated from the valve seat 17 whereby the magnetic attraction between the first ball valve 7 and the second ball valve 12 will be broken. As the first ball valve 7 moves upwards the second ball valve 12 will move downwards and both ball valves will thereby leave their valve seats and the drain outlet opening will be opened whereby waste water in the siphon will be free to leave the heat recovery device and run into the drain 4.

In order not to block the drain when the waste water is allowed to flow out of the heat recovery device, the second ball valve housing 14 is equipped with distance keeping means 19 whereby the second ball valve 12 is kept at a distance from a lower outlet of the ball valve housing 14. Hereby is assured that the waste water will have an unob- structed flow into the drain installation 4.

As the siphon 1 is filled with warm or hot waste water through the floor drain 10, the fresh water in the primary liquid circuit 2 will exchange energy with the waste water inside the siphon. Hereby is a preheating of the fresh water achieved.

In the figure the siphon 1 is equipped with additional inlets 18 for waste water from other sources.