Controlling the supply of electric current to a room
FIELD OF THE INVENTION 
     This invention relates, in one aspect, to a method of controlling the supply of electric current to an outlet or electrically powered device disposed in or adjacent a room and to an installation therefor, and, in a second aspect, to a combination plug and socket adaptor. The invention is of particular though by no means exclusive utility in relation to bathrooms, showers, kitchens, laundries and similar premises. 
     Electrically powered devices such as, for example, fans, room heaters, towel rails, electrically heated floors and carpets and the like may advantageously be adapted to the invention. 
     As an example, consider an exhaust fan in a bathroom. 
     The present exhaust fans for bathrooms have to be switched on and off manually by the occupier. If not switched on, then the room becomes steamy; if not switched off after a bath or shower or the like, then the fan continues to run, with consequent wastage of electricity. 
     SUMMARY OF THE INVENTION 
     This invention accordingly provides, in one aspect, a method of controlling the supply of electric current to an outlet or electrically powered device disposed in or adjacent a room wherein the current is controlled in response to variations in the temperature of a pipe for supplying water to a water outlet in the room. 
     In a second aspect of the invention, there is provided an installation comprising electrical power supply wiring associated with an electrical outlet or electrically powered device disposed in or adjacent a room, a water supply pipe having a water outlet in the room, and means to control the supply of electric current by the wiring to the electrical outlet or device in response to variations in the temperature of the water supply pipe. 
     The room may be a bathroom, the device a steam exhaust fan and the said means a thermostat secured to a hot water pipe supplying a tap at the bath, shower or washbowl and arranged to conduct current only when the temperature of the pipe exceeds a first predetermined value. When a person using the bath, shower or washbowl turns on the hot water then the hot water supply pipe will become hot and will close the thermostat which will, in turn, switch on the exhaust fan. 
     The fan will continue to extract steam-laden air from the room for some minutes after the hot water tap has been turned off; i.e., until the hot water supply pipe has cooled sufficiently to cause the thermostat to switch off the fan. 
     The said control means may be either (1) a part of the electrically powered device; i.e. rigidly or detachably connected to the device but located elsewhere or (2) provided with a separate special adaptor complete with either (a) an integral thermostat or (b) an external thermostat; i.e., a thermostat connected to the adaptor but located elsewhere. 
     With reference to item (1) supra, future exhaust fans for bathrooms could be manufactured and supplied with a thermostatic control unit forming part of the complete fan assembly. Alternatively, with reference to item (2) in the previous paragraph, existing types of fans including those already installed could be converted to automatic operation simply by fitting a separate special adaptor. In one form, the adaptor consists of a combined plug and socket which includes, or to which is attached, the thermostatic control unit. In general, the invention further provides a combination plug and socket adaptor for use in inserting an electric circuit element into series with an electrical power supply lead, the adaptor including at least two plug terminals and at least two socket terminals wherein a first of the plug terminals is directly electrically connected to a first of the socket terminals and respective second plug and socket terminals are electrically connected to separate outlet terminals or leads for bridging of the said second terminals by said circuit element. 
     To convert an ordinary existing type of bathroom exhaust fan to automatic operation, the combined plug and socket would be inserted between the existing plug and socket, and a thermostat bridging the said outlet terminals or leads would be attached to the hot water pipe. The existing manual switch would remain in the &#34;ON&#34; position. A time delay switch might be provided to determine switching from manual to thermoresponsive control. 
     The installation may include means to vary the control of the supply of the electric current in response to variations in ambient temperature in the vicinity of the pipe. This may comprise, for example, additional shunting thermostats having different temperature characteristics. 
     The abovementioned preferred thermostat whether included in the manufacture of the type of equipment envisaged or supplied as a separate unit, will have either a single thermostat or a plurality of thermostats in order to provide either a cheap product, which will be adequate in many applications, or a more expensive sophisticated product, which will provide better control, additional socket outlets and which will take into account the ambient climatic conditions. 
     The said control means need not necessarily be on or adjacent a pipe but may instead be in or on or near any other head source such as, for example, a stove or oven. 
     The word &#34;thermostat&#34;, as used herein, includes the singular and the plural; fixed range and variable range thermostats; bi-metal thermostats; and thermostats operated by liquid filled systems. Thermostats of each type may be included in combination. The word &#34;variable&#34; refers to manually adjustable thermostats and to thermostats which compensate for changes in ambient temperature. 
     The aforementioned adaptor may also of course be used for general purposes in conjunction with other types of circuit elements such as time, pressure, photo-electric, electronic radio-controlled, manual, magnetic, float, electrical and mechanical switches. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Particular exemplary and best methods of carrying out the invention will now be described with reference to four drawings provided herewith in which: 
     FIG. 1 depicts a bathroom installation in accordance with the invention; 
     FIGS. 2A and 2B are respectively perspective views of a known three-point adaptor and of an adaptor in accordance with the invention; 
     FIG. 3 is a circuit diagram for the installation of FIG. 1; and 
     FIG. 4 is a modified circuit diagram incorporating certain additional control features. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates, in side elevation, a bathroom installation in accordance with the invention in which an exhaust fan 5 mounted in the bathroom ceiling 9 is switched on and off by a thermostat 4 which is mounted on the hot water supply pipe. Present exhaust fans have a plug 6 which is inserted directly into a socket 7 and the electricity supply is controlled by a manual switch (not shown). In this example, the electricity supply is switched on and off by a special adaptor 2, which is connected by a length of cable 3, to the thermostat 4, mounted on the hot water supply pipe. Thermostat 4 is arranged to close for conduction of current only when a certain temperature is exceeded and to open when the temperature drops below a second temperature a few degrees lower than the closing temperature. 
     FIG. 2A shows the principal of existing plug adaptors and FIG. 2B shows an adaptor formed in accordance with the invention and having plug and socket terminals located to permit coupling with conventional three-point domestic sockets and plugs. In the latter a gap 18 between the plug active and the socket active terminals may be bridged via leads 21, 22 by the thermostat 4. (not shown on FIG. 2B). 
     FIG. 3 is a circuit diagram depicting the series connection of the thermostat 4 and fan 5 to the mains power supply. Additional equipment 20 such as a towel rail, a room heater and the like, can be controlled by the same installation by being wired across the fan as illustrated, or the additional equipment can be controlled by individual thermostats on the hot water pipe. 
     FIG. 4 illustrates an example in which a plurality of thermostats control a fan and other equipment in a bathroom during winter and summer conditions. During the latter, in some localities, high temperatures occur in the roof space; such temperatures necessitate ambient control; otherwise the fan and the other equipment may operate unnecessarily and continuously whenever high ambient temperature conditions occur around the pipe and thermostat. 
     In the example shown in FIG. 4, an ambient thermostat 10 will open as the temperature in the roof space increases, thereby isolating the pipe thermostat 11 having a closing temperature of 135°F and an opening temperature of 125°F. A second shunting pipe thermostat 12 having a closing temperature of 150°F and an opening temperature of 140°F will now control the fan and other equipment, including a room heater, illustrated. Thus, the fan and the other equipment will turn off in cold weather when the temperature of the hot pipe drops below 125°F but in very hot weather, when the ambient temperature may well be about 130°-135°F, they will be arranged to cease functioning when the temperature of the hot pipe drops below 140°F. 
     Also, when the ambient temperature reaches, say, 70°F, a further thermostat 13 is provided to open thereby isolating the room heater during warm weather.