GB2236381A - Heating system - Google Patents

Abstract

A heating system, such as a central heating system, is powered in normal operation by an AC source (8). The source also powers a battery charger (11) which charges a 12 volt battery (10). Upon an interruption of the mains supply the battery, now charged, is switched in and used to power the heating system, without any noticeable loss of power. Battery charger (11) also serves as an AC to DC converter for AC source (8) and all the components in the system are adapted to operate at a DC voltage such as 12 volts DC. <IMAGE>

Description

BEATING SYSTEM This invention relates to a heating system such as a central heating system and in particular it relates to a low power heating system which is operable even during periods of mains power failure.

Central heating systems generally utilize the combustion of a fuel such as oil, gas or solid fuelto heat water which is then circulated around radiators and a hot water system by electric pumps.

Such pumps are actuated by electric timers and controllers. The electric components operate at mains voltages and clearly, if there is a failure or interruption in the mains supply, the system does not function.

According to the present invention there is provided a central heating system wherein the electrical apparatus in the system is adapted to operate at DC.

Preferably the DC voltage is 12 volts DC so that the system can be run off a conventional car battery or other lead acid battery.

According to the present invention there is further provided a heating system including a power supply comprising a first input for an AC power source, means for converting the AC source to a DC source, a second input for a DC power source and means for switchably using a selected one of the DC power sources as an output.

Preferably, means are provided for using the source from the converting means to charge a battery when this source is used as the output. The second input is advantageously also the output to which a battery is connected for charging and this battery can then be used, when charged, as the DC power source applied to the second input.

Embodiments of the invention will now described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows schematically part of a central heating system; and Figure 2 is a circuit diagram of the supply of Figure 1.

Referring to Figure 1, a boiler 1 is used to heat water entering through a return pipe 2. The water, once heated, is pumped through respective pipes 3 and 4 by pumps 5 and 6. The water flowing through pipe 3 is used to heat water in a hot water tank and that in pipe 4 is passed round a system of radiators which each take heat from the water to warm the region around them. Alternatively, a common supply of heated water may be used to heat both the hot water tank and the radiators. Ultimately, the water returns through return pipe 2 to the boiler where it is re-heated. The boiler operates in conventional fashion by the combustion of a fossil fuel such as oil or gas under the control of an electrical system described below.

The control system is adapted to operate at 12 volts DC and includes two inputs: an input 8 for a mains electricity source, typically in the UK 240 volts at 50 Hertz, and an input 9 for a DC source which is preferably a car battery 10 or other lead acid battery. The inputs are both fed to a power supply unit 11. One example of this is shown in more detail in Figure 2 and comprises a transformer 12 for converting the 240 V AC signal to a 12 volt AC signal. A standard full wave rectifier such as a bridge rectifier 13 converts the 12 volt AC to a DC signal. The resulting DC signal is fed to one input of a switch S1 which receives a second input from a terminal connected to the 12 volt battery 10. Switch can therefore be used to select between the signal from the mains supply 8 or from the battery 10.The output from switch S1 is applied to power the electrical apparatus of the central heating system. The DC signal from rectifier 13 is also applied via a second switch S2 to a battery charging circuit 14. The output of the battery charging circuit is applied to battery 10 when actuated.

In general, switches S1 and S2 will be operated synchronously so that when switch S1 is in the position shown in Figure 2 S2 is also in the closed position shown. Thus, the signal deriving from the mains source will be used both to power the central heating and simultaneously to actuate the battery charger and thus to charge battery 10.

During this stage battery 10 is of course not providing power to the system. When, for example, an interruption in the main supply occurs, switches S and S2 are switched to their second position such that S2 is open and the battery 10 is not charged but instead the battery 10 and not mains source 9 is allowed to provide power to the system.

Alternatively, switch S2 may only be used when required and may be turned OFF when the battery is fully charged. Sensors (not shown) may be provided in the system to switch automatically S1 and/or when an interruption in the mains supply is detected. This can be achieved by standard techniques for example with electromagnetic latches.

The central heating system itself will not notice any significant difference between the outputs derived from the mains supply and from the battery.

The DC output from either one of these is applied to a low voltage controller/time switch 15 which receives inputs from a room thermostat 16 and a hot water thermostat 17 mounted in the hot water tank.

The boiler and respective pumps 5 and 6 are then actuated dependent, for example, upon ambient conditions, temperature of water in the tank and the time of day in a system including a time switch.

Because the system is a low voltage one, the cabel insulation can be of a lower specification than is normally required for a 240 volt AC system.

Thus, it can comprise flat cables placed discreetly behind wall coverings for example. An emergency lighting supply may also be powered by the battery and actuated when an interruption of the mains supply occurs. The battery may be fitted to the system at all times or alternatively could be attached via an extension cable or trailer socket when required.

Thus the battery could be one which is already fitted into a car or caravan and is only used for emergency use when necessary.

The battery charger is preferably of the type which can generate a varity of different charge voltages so that different types of battery can be used. Switches S1 and S2 may of course be integrated where appropriate.

Claims (10)

1. A heating system including a powc;r supply comprising a first input for an AC power source, means for converting the AC source to a DC source, a second input for a DC power source and means for switchably using a selected one of the DC power sources as an output.

2. A heating system as claimed in Claim 1 including means for using the source from the converting means to charge a battery when this source is used as the output.

3. A heating system as claimed in Claim 2 wherein the battery is connected to the second input such that in a first mode the battery is charged and the source derived from the AC source is used to power the heating system, and in a second mode the battery is used to power the heating system.

4. A heating system as claimed in any preceding claim including means for switching between the two power sources when an interruption in the AC source is noted.

5. A heating system as claimed in Claim 4 including means for automatically detecting an interruption and switching between the sources.

6. A heating system as claimed in any preceding claim including a lighting circuit connected to the second input for actuation with, and being powered by, the DC power source.

7. A heating system as claimed in any preceding claim wherein the DC power source applied to the second input is a 12 volt battery.

8. A central heating system wherein the electrical apparatus in the system is adapted to operate at DC.

9. A central heating system as claimed in Claim 8 wherein the DC voltage is 12 volts DC.

10. A heating system substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.