Patent GB-462255-A (GB)
Title: Improved mechanism for use in heating systems and the like
IPC: F24D19/10
Filed: 1935-09-04
Abstract: 462,255. Automatic control systems. DUNHAM CO., Ltd., C. A. Sept. 4, 1935, No. 24707. Convention date, April 6. [Class 38 (iv)] Temperature.-In a heating system comprising one or more heat dissipators, such as radiators, supplied with heating fluid through a valve actuated by mechanism automatically controlled by a member sensitive to the temperature or pressure of the fluid in a heat dissipator, a manual control panel is installed at a point remote from the said dissipator whereby selective operation of the system may be obtained. Alternative provision is thus made whereby the valve mechanism may be manually controlled, or set for automatic control by the said temperature or pressure sensitive device, or whereby the action of this automatic control may be adjusted (a) by a manually controlled switch or (b) by a further temperature sensitive device or devices ; in one form, this last control may be effected by a thermostat on an outside wall of a building, thus taking account of the rate of heat loss due to outside temperature, and in another, additional optional provision is made whereby a number of thermostats in different parts of the heated space may jointly co-operate in the adjustment of the automatic valve control. The application of the invention to the control of a vacuum evaporator is described also. A condensate pump may also be controlled automatically by the system. Fig. 1 shows a heating system using steam from a boiler 1 under the control of a valve 3 to supply radiators 6, 61, gases and condensate being drawn from a tank by a motor-driven pump 12, the condensate being returned to the boiler. A differential pressure controller 14 actuates the pump as required to keep the pressure in return line 9 below that in supply pipe 4. The pressure and temperature of steam in the radiators is controlled by a temperature or pressure-sensitive device C in one of the radiators, preferably the most distant. This operates through a " heat balancer " B upon a motor A controlling the setting of the valve 3. A control panel D in a convenient position is electrically connected between the heat balancer B and the valve motor A and also to a connection board 20 through which pass connections from a thermostat E in the space being heated and a thermostat F on the outer wall of such space. The valve motor is actuated by two rotors associated with separate stators arranged so that the torques are opposed and the control is effected through a solenoid switch which selectively energizes the stators. This switch is actuated by selective energization of two solenoids by a balanced-solenoid switch, both windings of which are constantly energized but shunted by reactances which are simultaneously variable in opposite senses by the control element. The movement of the motor varies other resistances in shunt with the solenoids to annul the control effect after the required movement of the valve has been made. This principle of control is also employed for the motor which adjust the action of the heat balancer B. The heat balancer comprises a lever 149 actuated by fluid pressure within an expansible vessel communicating with a hollow member 142 containing a heat responsive fluid and enclosed in a protective casing within the radiator. The lever 149 is thus actuated in dependence on the temperature of the heating fluid in the radiator and its movement is dependent on a compression spring which is adjustable by means of a cam 164 turned by the motor M. The lever 149 actuates contact members 88. 89 moving over separate resistance elements R6 which are separately connected to two lower terminals of a switch S2 on the control panel D in the arrangement shown in Fig. 5. The upper contacts of the switch S2 are connected to the ends of a resistance R5, the co-operating contact of which is adjustable by hand. A thermostat F actuates the contact arm of a similar resistance R3 and is placed on the outer wall of the building being heated, and the resistance R3 is connected to the lower contacts of a switch S1 on the control panel, the upper contacts of which are connected to a further hand adjusted resistance R2. The arms of the switch S2 are connected to solenoids controlling the valve setting motor A and the arms of the switch S1 to the solenoids controlling the heat balanced motor M. With the switch S2 in its upper position the valve can only be adjusted by hand from the control panel resistance R5. In the lower position of the switch the control of the valve is transferred to the heat balancer, and the temperature of the radiator is automatically controlled. If the switch Sl be set on its upper position, the action of the heat balancer will be adjusted according to the setting of the manually controlled resistance R2, and with the switch S1 in its lower position this adjustment will be effected by the thermostat F according to the rate of heat loss from the building. In a modification, Fig. 8, room thermostats E are adapted to participate in the control. The resistances of these thermostats like that of the heat balancer are in two sections and like sections of each thermostat are connected in series by the connection board 20. A switch S3 is added to the control panel D and the connections made provide as follows. With switch S2 up the valve is adjustable only by the manual control R5, with S2 down the automatic controls put in operation are selectable as follows. With S3 in its upper position the resistances of the thermostats E control the valve motor and the resistance R6 and the heat balancer is short-circuited and ineffective. Thus, the system is controlled by the average room temperature only. With S3 in its lower position the resistances of the room thermostats E are short-circuited and ineffective and the resistance R6 is operative so that the valve is controlled entirely by the heat balancer. If S3 be moved to its open position, the heat balancer resistance R6 and the resistances of the room thermostats are in series and the system is controlled in response to the average of the several temperatures of the room and of the fluid in the radiator 6<1>. In all cases in which the heat balancer is operative the temperature in the radiators can be adjusted either by the manual control R2 or by the thermostat F. The heat balancer lever 149, Fig. 5, is adapted to actuate a switch 214 controlling solenoids which snap over switches controlling the pump motor so that the exhausting pump is stopped at such times as the valve 3 is closed or partially closed. The adjusting cam 164 also operates a limit switch 181 when it is in its lowest position so that the resistance member 86 of the resistance R6 is short-circuited to effect a complete closure of the valve 3. In the application of the system to a vacuum evaporator, the temperature or pressure sensitive device C is installed in the outlet pipe from the evaporator coil and a thermostat in the evaporator acts jointly with the heat balancer to control the operation of the valve supplying heating fluid, manually adjustable control resistances determing the temperature to be maintained in the heating coil.