GB2591215A - Improvements in hot water supply - Google Patents

Abstract

The programmer (100, figure 1) is used with a hot water supply system including a hot water recirculation pump. The programmer sets ON and OFF times for the system and includes a control device 400 to intermittently operate the recirculation pump when the hot water supply is set to ON. Ideally the control device 400 includes a 555 timer-oscillator integrated circuit 402. The programmer can be used with hot water supply systems having a continuous operation circulation pump such that the control device, in operating the circulation pump intermittently instead of continuously during a hot water supply demand, improves efficiency of the system overall.

Description

IMPROVEMENTS IN HOT WATER SUPPLY

This invention concerns hot water supply systems, particularly but not necessarily exclusively open-vented or unvented systems with a hot water tank, for use in large domestic premises, in which the hot water is circulated around the system to avoid or at least reduce the need to run off water which* has been stationary and has cooled in the system before hot water is available at a tap of the system.

It is commonplace for hot water supply systems to include an electronic programmer operable to set times for the water heater of the system (and, commonly, of an associated central heating system) to switch ON and OFF automatically. Thus, typically, the water heater may be ON for part of the morning and for part of the evening, and OFF for the rest of the day and through the night. The set times may vary, eg between weekdays and weekends, and the programmers may include provision for settings to be overridden, advanced or manually adjusted, for instance.

It is also common, and increasingly so, for hot water systems to include a recirculation pump which in use returns to the water heater hot water not drawn off through a tap. This provides users with hot water on demand, rather than their having to wait for static water which has cooled in the system to flow through the tap before the hot water arrives.

Those skilled in the art will readily understand that continuous operation of a recirculation pump is inefficient, even if limited to times when the water heater is switched ON. To improve efficiency there have been several prior proposals for a recirculation pump to include a timer that causes it to run intermittently. Japanese patent application JP2001065898 describes a recirculation pump including a timer that operates on a cycle of two minutes ON and eight minutes OFF. United States patent applications US20111231022 and US2018180303 each describe a recirculation pump including a timer that operates on a so-called pulse mode in which it is ON for 75 seconds and OFF for 15 minutes. These prior systems all call for a recirculation pump with built-in controls for the pulsed/intermittent operation, and such pumps are expensive both to buy and to fit. Also, users of existing systems including a recirculation pump without pulsed/intermittent operation will be reluctant to discard it and will likely perceive its replacement by a pulsing/intermittent pump as wasteful.

It is an object of the present invention to provide intermittent operation of a recirculation pump easily and at substantially less cost than heretofore. Thus according to a first aspect of the invention there is provided a programmer for a hot water supply system including a recirculation pump for the hot water, which programmer is operable to set ON and OFF times for the hot water supply system and incorporates an electronic control device configured and arranged for connection to the recirculation pump and operative thereon to control the recirculation pump for intermittent operation when the hot water supply is set to ON.

The invention will now be described by way of example only with reference to the accompanying schematic drawings in which -Figure 1 illustrates a generalised form of known programmer for a hot water system and an associated central heating system, viewed from the front; Figure 2 illustrates the internal wiring of the programmer of Figure 1; Figure 3 illustrates an elementary hot water system to which the invention may be applied; and Figure 4 is a circuit diagram of an electronic control device for incorporation in the programmer of Figure 1 according to the invention.

Referring to Figure 1 the programmer 100 illustrated therein comprises a housing 102, a display 104 and a variety of user-operable controls. Whilst the programmer 100 is configured and arranged to control both hot water and central heating, as is conventional, the present invention is concerned with the control of the hot water, and features of the programmer illustrated in Figure 1 relating solely to the control of the central heating are not referenced in the following description, and can be ignored herein.

The display 104 is an LCD screen configured and arranged to display the day of the week, date and time, and the operating states of both the hot water system and the central heating system as, typically, AUTO (meaning a programming state in which times are set for the system to turn on and off automatically twice a day), ONCE (meaning a programming state in which the system is set to come on at the first set time and off at the last set time), CONTINUOUS (meaning a programming state in which the system is set to stay on regardless of the set times) and RUN (meaning the system is operative according the programme entered). The operating states of the hot water system and the central heating system appear respectively to the left and to the right of the display 104 as shown in Figure 1 and as indicated on the casing 102.

The programmer 100 includes a slider 106 movable by a user between four positions, marked as indicated in Figure 1, with respective detents to locate the slider 106. The first position of the slider 106 is marked as shown in Figure 1 by a clock face, and in this position day, date and time can be entered into the programmer by the user. In a second position marked CH in Figure 1, a programme can be entered for the central heating. Figure 1 shows the slider 106 in its third position, marked HW, and in this position a programme can be entered for the hot water. When the slider 106 is moved to its fourth position, marked RUN as shown in Figured 1, the entered programme is put into action.

The programme for the hot water system is entered as follows.

- The slider 106 is moved into the HW position, and a message "SET HVV" appears transiently on the display 104.

- A message "SET FIRST ON-TIME" then appears on the display together with a flashing indication of the first day of the week ("SUN") and of the time when the hot water comes ON that day. To change the time when the hot water comes on the same day, the user presses the + button 108 and the -button 110 alternatively, followed by the OK button 112 when the desired ON time is displayed.

-If the user does not wish to change the time when the hot water comes ON that day, he/she presses the OK button 112, and a message "SET FIRST OFF-TIME" flashes together with the time when the hot water goes OFF the same day. To change the time when the hot water goes off (for the first time) the same day, the user presses the + button 108 and the -button 110 alternatively, followed by the OK button 112 when the desired OFF time is displayed.

-The second ON time and the second OFF time can then be entered in the same way.

-When this has been done for the first day of the week, pressing the OK button moves the programme on to the second and subsequent days.

-When all the desired ON and OFF times have been entered, moving to the slider to the RUN position puts the hot water system into operation under the programme entered into the programmer 100.

For completeness it will be understood that, although not part of the present invention, the central heating can be programmed in a way similar to that described above for the hot water. Also, when the hot water is ON, a lamp 114 on the programmer 100 is illuminated and when the central heating is ON a lamp 116 is illuminated.

Stop and start buttons 118 and 120 on the programmer 100 enable a recirculation pump for the hot water to be alternatively rendered operative and inoperative by a user, as will be described in more detail hereinafter.

An internal wiring diagram 200 for the programmer 100 is shown in Figure 2, and is deemed self-explanatory.

Turning now to Figure 3, the elementary hot water system 300 shown therein includes a water heater 302 supplied with water from the mains 304 and operated automatically by the programmer 100 (Figure 1). When the water heater 302 is ON, a recirculation pump 306 pumps water from the water heater 302 around a circuit including downstairs and upstairs supply lines 308 and 310 feeding taps, showers, appliances and other outlets 312. (It will be understood that the number and usage of the outlets 312 will vary with the house or other premises in which the hot water system 300 is installed). The circulated water returns to the water heater 302 through return lines 314 and is heated again.

The direction of flow is indicated by the arrows in Figure 3, from which it is apparent that each of the outlets 312 has more or less instant access to hot water from the water heater 302 as long as this is ON and the recirculation pump 306 is operative.

It is wasteful of power to run the recirculation pump continuously when the water heater 302 is ON. Accordingly the invention provides an electronic control device incorporated in the programmer 100 of Figure 1 and configured and arranged for connection to the recirculation pump 306 operative thereon to control the recirculation pump for intermittent operation when the hot water supply is set to ON.

A control device 400 according to the invention has a circuit diagram as shown in Figure 4. The control device 400 utilises a 555 timer-oscillator 402. This is an integrated circuit (IC) of long standing which is very readily available.

The timer-oscillator 402 is an 8-pin IC comprising first and second comparators, a flip-flop and a high current output stage. The pins of the IC used in the invention are as follows.

Pin 1, Ground, connects to the negative (OV) line.

Pin 8, VCC connects to the positive supply voltage (+12V).

- Pin 3, Output, delivers to the base of an NPN transistor 404 an output which is either low (very close to OV) or high (very close to 12V). The form of this output is determined by the connections to the other pins.

- Pin 2, Trigger, starts the timer when the voltage on Pin 2 drops below one third of the supply voltage and creates a high output from Pin 3.

-Pin 5, Control, connects to ground by way of a capacitor 406 that serves to smooth any fluctuations in the supply voltage that might affect the operation of the timer.

- Pin 4, Reset, must be connected to the supply voltage for the timer to operate. The timer stops if Pin 4 is grounded (even momentarily). The timer can then be triggered to start again by way of Pin 2.

[For completeness it may be noted that, although not used in the present invention, the remaining pins of the IC are: Pin 7, Discharge, used in conjunction with a resistor to control the timing interval; and Pin 6, Threshold, which monitors the discharge voltage.] In addition to the NE555 timer chip 402, the other control circuit components are: a BC108 transistor 404; a 0.01pF capacitor 406; a relay coil 408; a 1N4007 diode 410; and two 1k0 resistors 412 and 414. Those skilled in the art will be readily able to construct a control circuit with such components or to use components of different values to generate a timed output to the recirculation pump of a form appropriate to the system (eg, most simply, a square wave with a mark-space ratio of 1 and a duty cycle of 50%).

Stop-start control is provided by the buttons 118 and 120 added to the programmer 100 as shown in Figure 1.

Incorporated in a programmer, the control circuit of Figure 4 can be powered from the mains electrical supply thereto by way of a step-down transformer and rectifier, but preferably and more conveniently it uses the existing 12V supply of the programmer. The timed output is adjustable time ON and time OFF.

It will now be understood that the invention adapts the hot water output signal of a conventional programmer to provide an intermittent output to a recirculation pump. This makes for improved efficiency as the pump and associated parts of the system do not run constantly when the hot water is ON.

The cycle time can be adjusted by appropriate choice of component values in the control circuit, eg to 10min or such other period as will ensure that the hot water does not become unacceptably cold when the pump is not running.

As described, the electronic control device of the invention is a self-contained addition to a conventional programmer. However, it could alternatively have an interface to the programmer and/or a link to a remote temperature sensor in the hot water system.

Finally, whilst the control circuit as shown and described includes a dedicated relay, a relay included in an existing programmer could be used with some additional circuitry or revised programming of the programmer.

Claims (6)

1. CLAIMSThe invention claimed is: 1. A programmer for a hot water supply system including a recirculation pump for the hot water, which programmer is operable to set ON and OFF times for the hot water supply system and incorporates an electronic control device configured and arranged for connection to the recirculation pump and operative thereon to control the recirculation pump for intermittent operation when the hot water supply is set to ON.
2. 2. A programmer as claimed in Claim 1 wherein the electronic control device includes an oscillator including a 555 integrated circuit.
3. 3. A programmer as claimed in Claim 1 or Claim 2 wherein said control device is operative to switch the recirculation pump off when the hot water supply is set to OFF.
4. 4. A programmer as claimed in any of Claims 1 to 3 enclosed in a casing which also contains said control device.
5. 5. A programmer as claimed in Claim 4 including manual controls accessible on or through said casing to programme the hot water supply system and said control device.
6. 6. A programmer as claimed in any preceding claim wherein said programmer and said control device have a common power supply.