US2353921A - Control system for unit heaters - Google Patents

Description

July 18, 1944. w. M. MYLER, JR I CONTROL SYSTEM FOR UNIT HEATERS 1 Filed Nov. 25, 1942 3nvent or Wdziw (Ittomeg Patented July 18, 1944 CONTROL SYSTEM FOR UNIT HEATERS William M. Myler, Jr., Columbus, Ohio, assignor to General Properties Company, Inc., Toledo, Ohio, a corporation of Delaware Application November 25, .1942, Serial No. 466,960

2 Claims.

In air heaters of the type adapted to be hung in the room or enclosure to be heated and comprising a gas fired radiator and a motor driven fan for forcing air past the radiator, the usual control system is such that when the fan motor is energized the burners for the radiator are automatically turned on. However, durin certain seasons of the year the weather may be such as to make fan operation without heat desirable during a portion of the day and fan operation with heat desirable during another portion of the day as durtinuously, such systems are not well adapted to permit a rapid changeover from one system of operation to the other because if the system is I operating as a heating system in which the fan and burner operate simultaneously under the control of a room thermostat it is necessary to manually shut off the gas supply to the burners in order to obtain fan operation without heat. In

7 reversing the procedure the gas must be manually turned on and the pilot and burners relighted so that normal heating operation may again be obtained. Since these appliances are usually suspended type units which require the use of a step ladder to give access to the units in order to be 1 able to turn the burners on or ofi and to light the pilot it is obvious that the changeover from one system of operation to the other is not a con- 1 venient operation.

It is the object of the invention to provide a control system which may be operated by a suitable manually operated electric switch located at any desired convenient location which will provide instantaneous changeover from the usual operating system wherein the fan and the burner operate simultaneously under the control of a room thermostat to a system wherein the fan runs continuously and heat may or may not be liberated depending upon the call of the room thermostat for heat.

The single figure of the accompanying drawing represents diagrammatically a unit heater with the control arrangement of my invention applied thereto.

The heater itself is commonly known as a unit heater and comprises a casin 5 wherein is housed a radiator comprising a plurality of laterally spaced tubes 6 which are oblong in cross sec-' tion, each tube being individually fired by a gas is a waste gas manifold which discharges into a vent pipe 9. Concentric with an opening in the back side of the casing is a motor driven fan Ill for forcing air past the radiator tubes, it being understood that the front side of the casing is open for the outflow of the forced air, said front side being shown as provided with louvres l l. The fan motor is indicated at l2. The gas burners receive gas from a gas manifold M to which gas ,to the fan motor l2.

, is supplied by a conduit l5 provided with a control valve H which is normally automatically opened by an electrically operated device [8 (which may be a solenoid) when power is applied to the fan motor. The gas conduit ahead of the gas valve I! has been shown as provided with an ordinary hand operated shut-oil valve I9. In the conventional control system for the heater it is necessary when fan operation without heat is desired-to close the shut-off valve is because in normal operation; as already stated, the device l8 will open the gas valve ll when power is applied A pilot for igniting the burners is indicated at and a pilot thermostat at PT, this thermostat being adapted to open and close a switch 2 l, the switch being normally closed when the pilot is burning.

In case the gas valve I! should fail to close after power to its operating device [8 has been shut off, the radiator is likely to be damaged by overheating. To provide for this contingency it is'usual to provide a thermostat (not shown) which is responsive to overheat temperature of the radiator for operating a control switch 22 for restarting the fan motor so that the fan will force air over the radiator in the usual way as long as the overheat condition exists,

The control system of the present invention comprises a hand operated double-pole double burner 1 therebelow. At the top of the radiator throw switch 23 of which the switch proper is indicated at 24, the same comprising blades 21 and 28 turnably mounted at points 29 and 30, respectively, and connected at their free ends by the usual handle bar. The two upper fixed contacts for the switch blades are indicated at 33 and 34 and the two lower contacts at 35 and 35. The upper left hand contact 33 and the lower right hand contact 38 are connected by a wire 31 and the upper right hand contact 34 and the lower left hand contact 35 are connected by a wire 38. The power line wires are indicated at 39 and 40, the same being shown as terminating at binding posts 4| and 42, respectively. A wire 43 leads from the binding post 4| directly to the fan motor l2 and the return wire 44 from the motor leads directly to the point 29 of the main switch 23.

electrically connected by the switch blade 21 with i the result that the fan motor |2 will be energized.

A room thermostat is indicated at RT, the same comprising a switch 25 for closing a circuit between wires 48 and 41 when said thermostat calls for heat, said wires leading from the points 29 and 30 of the main switch 23. The pilot thermostat switch 2| and the device l8 which operates the gas valve ll are connected in series by a wire 49 which leads from the power line binding post 4| to a contact 48 which comprises part of the overheat control switch 22. A wire 5| leads from the point 5|] of the overheat switch 22 to the upper left hand contact 33 of the main switch 23. The movable element of the overheat switch 22 is indicated as a blade 22 which is turnable about the point 50 and which is normally in electrical engagement with the contact 48 except when the radiator of the heater is overheated when it moves over into engagement with a contact 52. Leading from the contact 52 to the binding post 42 in the power line is a wire 53.

Assuming now that the switch element 24 of the main switch 23 is in down position for fan operation and that the room thermostat RT calls for heat, the device l8 will then be energizedthe power circuit being as follows: wire 45, blade 21, wire 46, switch 25, wire 41, blade 23, wires 3? and 5!, switch blade 22', and wire 49. It will thus be seen that when the main switch 24 is in down position, not only will the fan motor always remain energized but heat will automatically come on as needed to satisfy the room thermostat RT.

Assuming next that the main switch 24 is in up position, and that the room thermostat RT calls for heat, the fan motor l2 and the device i3 will simultaneously be energizedthe power circuit for the fan motor |2 being wires 45 and 38, biade 28, wire 41, switch 25, and wires 46 and 44; whereas the power circuit for the device |8 will be wires 45 and 38, blade 28, wire 4?, switch 25, wire 46, blade 21, wire 5|, switch blade 22, and wire 49 and the switch 2| in the latter. When the room thermostat RT has been satisfied, power to the fan motor and to the device |8 will be automatically cut off, inasmuch as the room thermostat switch 25 controls both power circuits.

If while the main switch 24 is in up position and after the room thermostat 32 has been satisfied (thereby causing the fan motor l2 and the device I8 to be deenergized), the fuel control valve I! should stick open thereby causing the radiator to become overheated, the switch element 22 of the overheat switch 22 will move over into engagement with the contact 52 thereby establishing a new closed circuit for the fan motor as follows: wire 53, switch blade 22', wire 5|, switch blade 21 and wire 44 to the fan motor. When the radiator has cooled down as a result of such fan operation, the switch blade 22' will again automatically move over into engagement with contact 48 thus deenergizing the fan motor.

What I claim is:

l. The combination with a space heater comprised of a radiator, a motor driven fan for forcing air past the radiator and an electrically operated device for controlling the application of heat to the radiator, of a double-pole multipleposition switch, means comprising said switch when it is in one of its closed positions for making ready a first power circuit to said electrically operated device and for closing a power circuit to said fan motor so that the latter will run irrespective of whether or not the said first power circuit is open or closed, means including a room thermostat for controlling the opening and closing of the said first power circuit, means comprising the said switch when it is in a second of its closed positions for making ready 2, power circuit common to said fan motor and to said electrically operated device, and means comprising sad room thermostat for controlling the opening and closing of the last mentioned circuit.

2. The combination with a space heater comprised of a radiator, a motor driven fan for forcing air past the radiator, burner means for heating the radiator, a fuel control valve for the burner means, and an electrically operated device for opening said valve, of a double-pole double-throw switch, means comprising said switch when it is in one of its closed positions for making ready a first power circuit to said electrically operated device and for closing a power circuit to said fan motor so that the latter will run irrespective of whether or not the said first power circuit is open or closed, means including a room thermostat for controlling the opening and closing of the said first power circuit, means comprising the said switch when it is in a second of its closed positions for making ready 2. power circuit common to said fan motor and to said electrically operated device, and means comprising said room thermostat for controlling the opening and closing of the last mentioned circuit.

WILLIAM M. MYLER, JR.

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