GB2213242A

GB2213242A - Water heaters

Info

Publication number: GB2213242A
Application number: GB8829383A
Authority: GB
Original assignee: GIANNONI Srl
Current assignee: GIANNONI Srl
Priority date: 1987-12-17
Filing date: 1988-12-16
Publication date: 1989-08-09
Anticipated expiration: 2008-12-16
Also published as: GB2213242B; NL8803074A; GB8829383D0; IT1223519B; IT8723068A0

Abstract

A method whereby in a water-heater of the instant type, in which a primary circuit (4) for supplying home heating hot water and a secondary circuit (11) for supplying hot sanitary water are in mutual heat exchange relationship through a heat exchanger (10), the latter is cut out from the secondary circuit (11), by a bypass 17 including a valve 18 responsive to temperature sensor 19, until the temperature of the water in the primary circuit (4) reaches a predetermined value. Thus, the heating time of the primary circuit water, and hence the wait time for delivery of hot sanitary water from the water-heater (1), can be shortened. <IMAGE>

Description

DESCRIPTION This invention relates to a method of shortening the wait time for the deLivery of hot sanitary water from a water-heater of the instant type including a primary water circuit adapted to supply hot water for home heating, a gas burner or the like means of heating the water being circulated through said primary circuit, a secondary water circuit adapted to supply hot sanitary water, and a heat exchanger whereat said primary and secondary circuits are in mutual heat exchange relationship to heat the sanitary water.

As is known, the generation of hot sanitary water for delivery from the secondary water circuit of a water-heater of the above type is initiated by a utilization tap of the sanitary system served by said water-heater being opened. The sanitary water in the secondary water circuit is heated by the hot water which is circulated through the primary water circuit of the water-heater.

Now, when the water in the primary water circuit intended for home heating happens to be hot already (burner on), as would be the case during the winter months, the wait time for the delivery of hot sanitary water through a utilization tap is virtually nil.

When, by contrast, the water in the primary circuit is cold (burner off), as would be the case during the summer months, said wait time, albeit a short one, still is a significant amount.

In fact, on opening a utilization tap in the sanitary system served by the water-heater referred to, the gas burner is ignited and the water in the primary circuit begins to be heated and will transfer some of the heat, as progressively acquired, to the sanitary water in the secondary water circuit, this water being supplied continuously and not utilized before it reaches a desired temperature.

The need has been particularly felt for some time to minimize, if not suppress, said wait time, both to provide improved facilities for the user and to prevent wasteful consumption of drinking water.

It has been suggested for this purpose of having the water in the primary water circuit heated at all times, but a technique stemming from this suggestion is recognized to have the drawback of an excessively high energy input and of enhanced formation of calcareous deposits within the water-heater water circuits.

It has also been proposed of providing the water-heater with a heat storage arrangement wherein hot water from the primary circuit could be stored up, but this proposal entails the drawback of a !considerable increase in the water-heater size and manufacturing costs.

The problem underlying this invention is to provide a method of significantly shortening, if not suppressing altogether, the wait time for the delivery of hot sanitary water from the moment the burner of an instant water-heater is activated, while overcoming the prior drawbacks.

This problem is solved according to the invention by a method characterized in that the exchange of heat between the primary and secondary circuits of said water-heater is inhibited with the water in said primary circuit at a lower temperature than a predetermined value, the exchange of heat between said primary and secondary circuits being re-established on said value being exceeded.

In accordance with one aspect of this invention, the heat exchange between the primary and secondary water circuits of such a water-heater is inhibited by cutting out said heat exchanger from the secondary water circuit.

The features and advantages of a method according to this invention will become more clearly apparent from the following detailed description of an exemplary embodiment thereof, given with reference to a wall-mounted water-heater of the instant type as shown in fragmentary and diagramatic form in Figure 1 of the accompanying drawing.

With reference to the drawing figure, generally indicated at 1 is a wall-mounted water-heater of the instant type comprising a primary water circuit 4 for generating and supplying hot water for home heating purposes, and a secondary water circuit 11 for generating and supplying hot sanitary water.

The primary circuit 4 is connectable to a home heating system (not shown) via delivery and return Lines 5 and 6, respectively. Said primary circuit 4 includes a water circulation pump 12 the suction line 1Za whereof is in liquid communication with the return line 6, while the delivery line 12b is connected for water conduction to a first heat exchanger (or primary heat exchanger) 7 which is supported in a position overLying a gas burner 3.

Starting from the outlet end of the heat exchanger 7, the primary circuit includes a three-way valve 9, of which a first way is in communication with said primary heat exchanger 7 via a bleeder valve 8, a second way is connected for water conduction to the delivery line 5, and a third way is connected for water conduction to a second heat exchanger (or secondary heat exchanger) 10.

The secondary heat exchanger 10 is in turn connected, via an outlet line 12c, for water conduction to the suction line 12a of the water circulating pump 12.

The secondary water circuit 11 is connectable to a sanitary water supply system (not shown) by return and delivery lines 14 and 16, respectively. Such lines 14 and 16 are in liquid communication with the secondary heat exchanger 10. By way of illustration, the lines 14 and 16 are mutually connected for water conduction to a pipe coil section 15 extending through the secondary heat exchanger 10 of which it is an integral part.

To schematize, the primary 4 and secondary 11 water circuits of the water-heater 2 may be said to share the secondary heat exchanger 10, through which said water circuits are put in mutual heat exchange relationship.

In the secondary water circuit 11, the lines 14 and 16 are interconnected by a bypass line 17 of the secondary heat exchanger 10. Mounted in this line 17 is a valve means 18 for cutting off the flow of sanitary water, such as a solenoid valve, under control by a temperature sensor 19 mounted in the line 12c of the primary circuit 4 from the outlet end of the heat exchanger 10. In a preferred embodiment, the pipe coil section 15 of the secondary circuit 11 is sized to produce much larger load losses than those produced by the bypass Line 17, thereby with the solenoid valve.18 open, almost all of the sanitary water flow goes through the last-mentioned line, which results in the heat exchanger 10 being cut out from the secondary water circuit 11.

It stands to reason that in an alternate embodiment, the secondary circuit 11 may be provided with some other valve arrangement for cutting off the sanitary water flow effective to cut out therefrom the coil pipe section 15, that is the heat exchanger 10.

The water-heater 1 further includes a flow sensor 20 mounted in the water intake, line 14 to the secondary circuit 11 and operative to control ignition of the burner 3 upon a sanitary water utilization tap being opened.

During thc- summer season, and in any case where the home heating function is not required, the burner 3 of the instant water-heater just described would be in an off state, and the water in the primary circuit cold. Under this condition, the solenoid valve driven by the temperature sensor 19 is open.

Upon demand for hot sanitary water, as by opening a utilization tap, the flow of water through the secondary circuit 11 takes place through the bypass line 17, with the secondary heat exchanger 10 fully or almost fully cut out from said circuit. Simultaneously with the opening of the utilization tap, the flow sensor 20 will instantaneously control the burner 3 to ignite, which initiates heating of the water being circulated through the primary circuit 4, including the secondary heat exchanger 10. Inasmuch as this heat exchanger 10 is cutout from the secondary water circuit 11, during the water heating in the primary circuit 4, no heat exchange takes place between this water and that in the secondary circuit 11. This condition is maintained until the water in the primary circuit 4 is brought to a predetermined temperature value.

On this value being reached, the temperature sensor 19 will control the solenoid valve 18 to close, which results in the heat exchanger 10 being connected back into the secondary water circuit 11. Thus, heat exchange conditions between the water being circulated through the primary circuit 4 and the sanitary water being circulated through the secondary circuit 11 are re-established.

By inhibiting the exchange of heat between the two, primary and secondary, circuits of the water-heater 1 during the initial heating period of the water circulated through said primary circuit, this water is able to achieve more rapidly its predetermined temperature value, and it has been found that the wait time at the sanitary water delivery tap can be, if not suppressed completely, cut down by more than 50% over what has been feasible heretofore.

Claims

1. A method of shortening the wait time for the delivery of hot sanitary water from a water-heater (1) of the instant type including a primary water circuit (4) adapted to supply hot water for home heating, a gas burner (3) or the like means of heating the water being circulated through said primary circuit (4), a secondary water circuit (11) adapted to supply hot sanitary water, and a heat exchanger (10) whereat said primary (4) and secondary (11) circuits are in mutual heat exchange relationship to heat the sanitary water, characterized in that the exchange of heat between the primary (4) and secondary (11) circuits of said water-heater (1) is inhibited with the water in said primary circuit (4) at a Lower temperature than a predetermined value, the exchange of heat between said primary (4) and secondary (11) circuits being re-established on said value being exceeded.

2. A method according to Claim 1, characterized in that the exchange of heat between the primary (4) and secondary (11) water circuits of said water-heater (1) is inhibited and re-established by respectively cutting out from and connecting back into the secondary water circuit (11) said heat exchanger (11).

3. An instant type water-heater comprising a primary water circuit (4) adapted to supply hot water for home heating, a gas burner (3) or the like means of heating the water being circulated through said primary circuit (4), a secondary water circuit (11) adapted to supply hot sanitary water and including a return line (14) and delivery line (16) for said sanitary water, a heat exchanger (10) whereat said primary (4) and secondary (11) circuits are in mutual heat exchange relationship to heat the sanitary water, characterized in that it comprises a line (17) extending between said return line (14) and said delivery line (16) and bypassing said heat exchanger (10), a cut-off valve means (18) mounted in said line (17) and driven by a temperature sensor (19) operative to sense the temperature of the water being circulated through said primary water circuit (4).

4. A water-heater according to Claim 3, characterized in that said temperature sensor (19) for sensing the temperature of the water being circulated through said primary circuit (4) is mounted in an outlet section (12c) of said circuit from said heat exchanger (10).