GB2175389A - Room heaters - Google Patents

Abstract

A master boiler radiator unit 10 in which electrical heating elements 19,20 in a flow boiler 17 are selectively controllable by a control circuit providing a presettable programmer 16, a presettable liquid temperature switch 55 and a thermostatic valve 32. <IMAGE>

Description

SPECIFICATION Room heaters This invention concerns heating apparatus generally of a kind comprising liquid heating means to heat a liquid, a heat emitter connected to the heating means by pipework, and a pump to circulate the liquid.

Various forms of such heating apparatus are known. For example, conventional domestic central heating systems in which the liquid heating means is a burner/boiler unit to burn fuel to heat the liquid. However, such systems require air inlets and exhaust flues, which can be difficult and expensive to instal, and have other disadvantages such as relatively high thermal outputs and need fuel supply systems which make such systems unsuitable for some application such as relatively small low-cost domestic dwellings. However, such domestic central heating systems offer the advantages of automatic operation and good heat distribution, especially in comparison with individual independent room heaters such as electric fires.

For use in dwellings, such as relatively small dwellings and those having mains electricity supplies but not gas supplies, there has been proposed a form of central heating apparatus in which the liquid heating means comprises a tank fitted with electrical heater units which each incorporate a respective thermostatic switch to control the unit. However, such apparatus has several disadvantages. For example, in one known form the tank is relatively small so that the response time is small, but if the demand ceases whilst the heater units are switched on the operating temperature can overshoot a maximum safe temperature before the individual thermostatic switches have time to respond to resultant rise in temperature of the heater units.In another form the tank is relatively large and serves to store heated water, but the apparatus requires a long time to reach a required operating temperature, i.e. it may have a slow response to demand.

Furthermore, because electricity can be a relatively expensive form of energy supply, and it has been proposed to use such relatively large tanks to store water heated, e.g.

at right, using electricity supplied on a lower priced 'off-peak" tarrif, and to further provide a supplementary heater to boost the temperature of the circulated water if needed, but such installations are bulky and expensive.

An object of the invention is to enable said disadvantages to be reduced or avoided.

According to the present invention there is provided heating apparatus comprising heating means to heat a liquid, a heat emitter connected to the heating means by pipework, a pump to circulate the liquid, and electrical control means; and wherein the heating means comprises a tank provided with a plurality of electrical heating elements, wherein the control means comprises a manually presettable time switch in a relay control circuit, relay means in said relay control circuit, and a thermostatic switch which is arranged to respond to the temperature of the liquid in said tank; and characterised in that: (a) the heat emitter forms part of a housing in which the heating means is disposed, (b) the relay means provides a plurality of relays in a power circuit for individual control of the heating elements; (c) the control means is manually presettable for selection of the number of elements to be energised; and (d) the thermostatic switch is manually adjustably settable for selection of limit to which the liquid is heated in the tank and is in series in said relay control circuit with said relay means and said time switch.

The heating apparatus may thus be made compact and self-contained in the housing, whilst permitting a user to select the heating temperature and the rate of heating, and thus the maximum rate power consumption, in any selected heating period.

The time switch preferably includes a respective program selector for each element, to permit said selection of the number of elements to be energised, as well as presettable period selector means.

Said elements preferably form parts of an immersion heater unit which is preferably disposed in said tank so as to be spaced apart from said thermostatic switch, so that the thermostatic switch and immersion heater unit are thermally de-coupled.

The thermostatic switch preferably has a remote sensor, and may be of a kind comprising a pressure operated switch mechanism connected by a capilliary tube to a bulb; and the bulb is preferably a close sliding fit in a socket in said tank so as to provide a short and large area conductive path for heat transfer between the liquid in the tank and a liquid in the bulb.

A safety temperature limit switch is preferably connected in series in said relay control circuit, and is or has a remote sensor mounted on said tank, the switch being set to open when a predetermined maximum safe operating temperature is reached.

The heat emitter preferably serves as a, or part of a, front wall of the housing.

The pipework preferably includes a restricted flow path, in series with the pump, between a return pipe to the tank and an output pipe from the tank; and a thermostatic valve, responsive to ambient temperature, in series with the heat emitter.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein: Figure 1 shows heating apparatus of the in vention in rear elevation; and Figure 2 is an electrical circuit diagram of control means of said apparatus.

The heating apparatus 10 shown in Fig. 1, is constructed to serve as a master boiler/radiator unit for use in a central heating system, but may be used on its own as space heating apparatus.

The apparatus 10 comprises liquid heating means 12, a heat emitter 13, pipework 14 a pump 15 and control means 16.

The liquid heating means 12 comprises a tank 17 of about or less than two litres capacity, and an electrical immersion heater 18 having a maximum heat output of about six kilowatts from two elements 19 and 20. The tank is formed to provide a socket 21, a water inlet 22 and a water output 23, and the socket 21 is disposed so as to be spaced apart from the immersion heater 18 by at least 10cm.

The heat emitter 13 is a Dia-Norm Diamond (TM) low water capacity central heating radiator modified to form a front wall of a housing 24 having end walls 25 and 26 and slotted top and bottom walls 27 and 28.

The pipework 14 comprises an output pipe 30 from the outlet 23 to the pump 15; an internal delivery pipe 31 from the pump 15 to the emitter 13 via a thermostatically actuated valve 32 having a portion outside the housing which responds to air temperature and is manually presettable; a secondary delivery pipe 33 for connection to other emitters; a return pipe 34 from the emitter 13 to the inlet 22; a secondary return pipe 35 for connection to other emitters; a shunt pipe or by-pass 36 which provides a restricted flow path between the pipes 33 and 35; and a drain cock 37.

The control means 16 (Fig. 2) comprises a timer switch unit 40 having terminals market L, N and 1 to 6. The unit 40 may be of known form, such as a Horstmann 425 "Diadem" (TM) time control providing a manually presettable timer 41, and two manually actuable mode selector switches 42 each providing four mode settings namely switched "on", switched "off", one switched on period per day, and two switched on periods per day, the timing and duration of which periods are determined by the setting of the timer 41.

The unit 40 controls a relay control circuit 43, and is connected by terminals L,2 and 5 to a live terminal of a power supply input connector 44 by a line 45 and a fuse F1. One switch 42 controls the mode of switching of the power supply to terminal 1 and line 46 for supplying power to the pump 15 and energising solenoid RS1 of a first relay R1; and the other switch 42 controls the power supply to terminal 4 and line 47 for supplying power to solenoid RS2; of a second relay R2. The unit 40 is arranged so that terminal 4 can only be energised if terminal 1 is also energised. The unit 40 is connected by the terminal 1 to a line 48 connecting the pump 15 to the neutral terminal of the power supply input connector 44; and solenoids RS1 and RS2 are connected by a common neutral line 49 to the line 48.

Relay R1 has controlled contacts RL1 which control the supply of power from the connector 44 via live line 50 to the element 19, and the relay R2 has controlled contacts RL2 between the line 50 and the element 20. The elements are connected in parallel by a neutral line 51 to the connector 44. The elements may be protected by a common power fuse 52, or by respective power fuses 53 and 54 indicated in broken lines.

The control means 16 further includes a manually presettable thermostatic switch 55 and a temperature limit switch 56 in series in the relay control circuit. The switch 55 may be of known form, for example, a Ranco C28 P1436 capilliary liquid expansion thermostat, which comprises a capilliary tube 57 leading to a bulb located in the socket 21; and comprises a temperature dial and knob 59 exposed at the outside of the end wall 25 above the unit 40. The limit switch 56 may be of known form, for example, a Ranco LP5.1039 limit thermostat having an actuating capilliary 60 which leads to the socket 21 to respond to the temperature in the socket. The switch 55 preferably has an upper setting limit of 90 C, and the switch 56 is preferably designed to open when exposed to a temperature of about 95"C.

The apparatus has several advantages and reduces or avoids the aforementioned disadvantages, in that, for example: (a) The switch 55 is accurate and fast in response to the set temperature being traversed, and responds substantially directly to the temperature of the liquid, e.g. water, in the tank without being significantly influenced by the actual temperature of any part of the immersion heater, whereby to inhibit excessive heating of the liquid, and therefore the switch 56 may have such a very high limit temperature setting because it is only required for safety in the event of a major failure of the switch 55: (b) The switches 55 and 56 are in the relay control circuit and are thus not subjected to the high supply currents to the elements, thus minimising the risk of unwanted heating of the switches 55 and 56 due to arcing or poor (resistive) contact of the contacts thereof: : (c) The fuse F1 can be matched to the electrical load of the pump, and controls the supply to the control circuit, so that breakage of the fuse F1 (and thus halting of the pump) automatically causes the relays to interrupt the power supply to the immersion heater: and (d) The control unit and the switch 55 afford the user considerable scope to vary the rate, period and temperature of heating of the liquid, and the rate of dissipation can be controlled by the valve 32, to give good control of the room heating and the rate and timing of power consumption.

The invention is not confined to details of the foregoing example and many variations are possible within the scope of the invention.

The wattage and number of elements (and the number of respective relays and mode selector switches) may be selected to suit the number of slave emitters (radiators) or other demands to be supplied. The size and arrangement of the tank may be varied, but it is preferred that the capacity of the tank should be about one litre for every two to four kilowatts rating of the heating elements installed in the tank.

Claims (7)

1. Heating apparatus comprising heating means to heat a liquid, a heat emitter connected to the heating means by pipework, a pump to circulate the liquid, and electrical control means; and wherein the heating means comprises a tank provided with a plurality of electrical heating elements, wherein the control means comprises a manually presettable time switch in a relay control circuit, relay means in said relay control circuit, and a thermostatic switch which is arranged to respond to the temperature of the liquid in said tank; and characterised in that: (a) the heat emitter forms part of a housing in which the heating means is disposed, (b) the relay means provides a plurality of relays in a power circuit for individual control of the heating elements; (c) the control means is manually presettable for selection of the number of elements to be energised; and (d) the thermostatic switch is manually adjustably settable for selection of limit to which the liquid is heated in the tank and is in series in said relay control circuit with said relay means and said time switch.

2. Apparatus as claimed in Claim 1, wherein said elements form parts of an immersion heater unit which is disposed in said tank so as to be spaced apart from said thermostatic switch.

3. Apparatus as claimed in Claim 1 or 2 wherein the thermostatic switch has a remote sensor in a socket in said tank.

4. Apparatus as claimed in Claim 1, 2 or 3 wherein a safety temperature limit switch is connected in series in said relay control circuit.

5. Apparatus as claimed in Claim 4 as appended to Claim 2 wherein the safety switch has a remote sensor located in said socket.

6. Apparatus as claimed in any preceding claim wherein the time switch includes a respective program selector for each element, to permit said selection of the number of elements to be energised, as well as presettable period selector means.

7. Heating apparatus substantially as hereinbefore described with reference to Fig. 1, or Figs. 1 and 2.