GB1568527A

GB1568527A - Water heater units

Info

Publication number: GB1568527A
Application number: GB1122/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-01-12
Filing date: 1977-01-12
Publication date: 1980-05-29
Also published as: FR2377586A1; DE2801014A1; NL7800347A; FR2377586B1; SE7800299L; DK155296C; DK155296B; JPS53111549A; DK6278A

Description

(54) IMPROVEMENTS IN OR RELATING TO WATER HEATER UNITS (71) I, ERIK MOLBECH, Sindalsvej 35, 8240 Risskov, Denmark, of Danish nationality, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to water heater of the flow-through type and of the kind specified in the introductory clause of claim 1. Normally, in such heaters, the consumption water is passed through a copper tube located inside an externally heat insulated container or cylinder provided with the inlet and outlet for the district heating water.The cold water inlet is connected to the water supply mains and the warm water outlet is connected to one or more warm water taps. In the district heating water connection is mounted a valve which may be a thermostatic valve controlled by a temperature sensor reacting on the cooling of the district heating water which takes place by the consumption of warm water.This regulation takes place with a certain time delay, and in practice, therefore, it is preferred to make the heating water valve controlled by a flow sensor mounted in the consumption water pipe so as to react instantaneously on warm tapping as far as both opening and closing is con cerred. In such a control unit the flow sensor may be adapted to effect either an or-off regulation of the heating water valve or by preference a gradual or proportional regulation correspoading to the actual water consumption at any time.The flow sensor, however, should be adapted to allow for a feeble flow of con sumpdon water without causing the heating water valve to open, as also well known from gas fired water heaters, whereby it is prevented that e.g. a dripping tap causes a constant heating of the heater and thus a waste of heating medium.

In many installations the pressure level of the heating medium such as the district heating water is generally higher than the supply pressure in the consumption water mains, and should an internal leak occur in the heat exchanger there will be a risk, therefore, that the heating medium may intrude into the consumption water pipe and get forced rearwardly into the consumption water mains and thus contaminate the water in the mains generally. To an increasing degree, therefore, it is offidally required that the water heaters are safeguarded against this risk, and it is a normal and close to hand solution to solve the problem by mounting a check valve in the cold water inlet of the heat exchanger.

However, by this solution is introduced another disadvantage, viz. that the amount of consumption water trapped between the tap or taps and the said check valve upon termma- tion of a warm water tapping will be unable to undergo the expansion caused by the latest introduced cold water now being heated by the surplus of heat energy in the latest introduced heating medium. In normal flowthrough heaters such a trapped volume of water will be unable to expand without causing damage to the pipe system, and the problem will arise every time the water tapping is terminated in normal use.

It is found necessary, therefore, to provide the heat exchangers with a security valve which opens each time the pressure in the trapped volume of consumption water exceeds a predetermined maximum, and this measure furthermore necessitates the use of a drain pipe installation between the outlet of the security valve and the drain. Thus, the use of the said check valve in the cold water inlet for safeguarding the water mains against intrusion of district heating water has in practice involved substantial additional installation costs.

It is the purpose of this invention to provide a water heater of the type refereed to, wherein the necessary safeguarding is obtained by simple means.

The invention is based on the simple idea that in case of an internal leak in the heat exchanger it is possible to prevent intrusion if the heating medium into the water mains by preventing access of the heating medium to the heat exchanger and maintaining the cold water inlet open in such a manner, without the use of the said check valve therein, that the water upcm termination of the tapping is not trapped and thus is freely expansible, whereby the said security valve and said drain pipe are made superfluous. The hindrance of intrusion of heating medium is easily obtained with the use of a regulation unit of the said known type comprising a heating medium regulation valve controlled by a flow sensor in the consumption water pipe, such that the heating medium inlet is kept closed whenever no warm water tapping is going on.Normally the heating medium system will be a closed and generally pressurized system, and heating medium may be prevented from entering the heat exchanger from the heating medium outlet or return side by means of either a check valve in the heating medium outlet or a regulation valve mounted in this outlet and controlled by the said flow sensor so as to be opened and closed together with the regulation valve in the heating medium inlet In accordance with these considerations the water heater according to this invention is characterized by the features stated in the characterizing clause of claim 1.As long as warm water is not being tapped from this heater the admission of heating medium is effectively prevented both from the inlet and from the outlet or return side of the heating medium system, and even though the cold water inlet allows for water to be forced outwardly therethrough and thus for said normal consumption water expansion to take place, the cold water inlet will nevertheless be safeguarded against extrusion of heating medium.

As long as warm water is being tapped the heating medium inlet valve will be open, but in case of an internal leakage the heating medium will now be mixed into the warm water being tapped and hereby cause discovery of the faulty situation without penetrating into the cold water mains.

The invention involves the further advantage that an exterior leak in the outer container or cylinder of the heat exchanger will result in extrusion of pressurized heating medium only as long as a warm water tapping is going on, as the supply of heating medium is terminated as soon as the tapping is terminated.

In the following the invention is described in more detail with reference to the accompanying drawing, which is a schematic illustration of a flow-through water heater according to a preferred embodiment of the invention.

The water heater shown is generally designated 2 and comprises an outer container or cylinder 4 having an inlet 6 for district heating water supplied through an inlet pipe 8, and an outlet 10 conected to a return pipe 12 of the district heating system. Inside the container 4 is provided a copper pipe 14 which at one end is connected to a supply pipe 16 for cold consumption water and at its opposite end is connected to a warm water pipe 18 communicating with one or more warm water taps 20.

In the district heating return pipe 12 is mounted a check valve 22 allowing the heating medium to leave the container 4, but preventing intrusion of heating medium into the container 4 from the retrun side of the district heating system. In the cold water inlet pipe 16 is mounted a flow sensor 24 operable to mechanically or otherwise detect a water flow in the pipe 16 in response to tapping of warm water, without the sensor 24 closing the pipe 16 in either direction when no tapping takes place. The flow sensor 24 is connected, mechanically or otherwise, with a regulation valve 26 in the inlet pipe 8 for heating medium such that this latter valve is opened in response to the sensor 24 detecting a flow of consump tion water and is closed as soon as the tapping of consumption water is terminated.For the invention it is unimportant whether the control of the regulation valve 26 is effected as an on-off-control or a control graduated proportionally to the intensity of the flow past the flow sensor 24, despite the latter control type being preferable in practice.

In normal use the sensor 24 will cause district heating water to be supplied to the heat exchanger 4 as soon as a water tapping is initiated, whereby the water is heated as desired and the district heating water is fed to the return pipe 12 through the check valve 22. When the tapping is terminated the sensor 24 will cause a complete closing of the regulation valve 26, whereafter the district heating water cannot flow into the heat exchanger, neither through the closed valve 26 nor through the check valve 22. As the sensor 24 does not dose the cold water inlet pipe 16 the latest introduced cold water will be able to expand out into the pipe 16 when it is heated by the latest introduced district heating water.

As the heating water correspondingly gets cooled it tends to undergo contraction, and this may cause an underpressure to arise in the container 4 because this is closed for access of new heating water; however, such underpressure is easily resisted by the walls of the container.

Should a leakage occur in the tube 14 inside the container 4 the pressurized district heating water may intrude into the tube only as long as warm water tapping is going on, since in that case the valve 26 is opened, and hereby the leakage will reveal itself by way of the warm consumption water being contaminated by the intruding district heating water. Generally the latter will be unable to build up such a pressure in the tube 14 as would be required for forcing the district heating water rearwardly out into the cold water inlet pipe 16, i.e. general contamination of the water mains is effectively prevented.

The use of the check valve 22 in the heating medium return pipe further involves the advantage that in case of a leak in the exterior wall of the container 4 the pressure inside the container will be rapidly relieved if the valve 26 is in its closed position, i.e.

as long as the water heater is not actually used, and new pressurized heating medium will be admitted only as long as warm water is being tapped. The damage caused by the leal heating water will thus be much less than if there was free access of heating water from the return pipe 12.

It will be understood that the check valve 22 may be substituted by a regulation valve catHrolled by the sensor 24 together with the valve 26, since its task is to ensure that the return pipe 12 is blocked against reverse flow whenever the inlet valve 26 is closed.

WHAT I CLAIM IS: 1. A water heater of the flow-through type comprising a heat exchanger having an inlet for cold conssmption water and an outlet for warm water as well as an inlet and an outlet for a liquid heating medium such as district heating water, and having automatic regulation means for opening and closing the flow of heating medium in response to detection of consumption of warm water, and security means being provided for preventing heating medium under pressure from flowing outwardly through the cold water inlet in case a leak should occur inside the heat exchanger characterized in that the regulation means are of the kind arranged to control the supply of heating medium by means of a flow sensor mounted in the cold water inlet and controlling a regulation valve in the heating medium inlet in such a manner that the latter is opened in direct response to water consumption and is fully closed when the consumption is zero or very low, said flow sensor being arranged so as to keep the cold water inlet at least partially open even during zero water consumption, and that a valve means, preferably a check valve, is mounted in the heating medium outlet so as to prevent heating medium from entering into the heat exchanger through said outlet at least when said regulation valve in the heating medium inlet is closed.

2. A water heater according to claim 1, characterized in that said valve means in the heating medium outlet is a separate regulation valve which is operatively connected with the regulation valve in the heating medium inlet so as to open and close concurrently with this inlet valve.

3. A water heater of the flow-through type substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The use of the check valve 22 in the heating medium return pipe further involves the advantage that in case of a leak in the exterior wall of the container 4 the pressure inside the container will be rapidly relieved if the valve 26 is in its closed position, i.e. as long as the water heater is not actually used, and new pressurized heating medium will be admitted only as long as warm water is being tapped. The damage caused by the leal heating water will thus be much less than if there was free access of heating water from the return pipe 12. It will be understood that the check valve 22 may be substituted by a regulation valve catHrolled by the sensor 24 together with the valve 26, since its task is to ensure that the return pipe 12 is blocked against reverse flow whenever the inlet valve 26 is closed. WHAT I CLAIM IS:

1. A water heater of the flow-through type comprising a heat exchanger having an inlet for cold conssmption water and an outlet for warm water as well as an inlet and an outlet for a liquid heating medium such as district heating water, and having automatic regulation means for opening and closing the flow of heating medium in response to detection of consumption of warm water, and security means being provided for preventing heating medium under pressure from flowing outwardly through the cold water inlet in case a leak should occur inside the heat exchanger characterized in that the regulation means are of the kind arranged to control the supply of heating medium by means of a flow sensor mounted in the cold water inlet and controlling a regulation valve in the heating medium inlet in such a manner that the latter is opened in direct response to water consumption and is fully closed when the consumption is zero or very low, said flow sensor being arranged so as to keep the cold water inlet at least partially open even during zero water consumption, and that a valve means, preferably a check valve, is mounted in the heating medium outlet so as to prevent heating medium from entering into the heat exchanger through said outlet at least when said regulation valve in the heating medium inlet is closed.