US1768805A - Unit-heater control - Google Patents

Description

July 1, 1930. w sw T 1,768,805

7 UNIT HEATER CONTROL Original Filed June 10, 1927 INVENTOR HAROLD W. SWEATT A TTORNEYE Patented July 1, 1930 UNITED STATES PATENT OFFICE HAROLD w. SWEATT, OF MINNEAPOLIS, MINNESOTA, ASSIGNOR T0 MINNEAPOLIS- HONEYWELL REGULATOR COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORRORA- TION OF DELAWARE UNIT-HEATER CONTROL Original application filed June 10, 1927,8erial No. 197,987. Divided and this application filed October 27,

1928. Serial No. 815,563.

This invention relates generally to improvementsin heat regulating devices and is partlcularly directed to the control of a circuit having a power driven fan, which fan is 7 associated with a heating unit such as a radiator for the purpose of circulating air heated by the radiator.

This application is divisional of m copending application, Serial Number 19 ,987, filed June 10th, 1927 for unit heater control.

In the usual systems in which the fan of a unit heater is controlled by a room thermostat, it happens that the fan is frequently operated when the radiators or heaters are cold. Inasmuch as these heaters are sometimes arranged adjacent the outer wall of a building and, inasmuch as conduits are often provided so that cold outside air may be delivered to the radiator, operation of the fan when the radiator is cold would result in a cold draft being forced into the building, or the fan would create a cold draft which is also undesirable. Moreover, inhot water systems, or in steam systems in which the drainage is imperfect, it may happen that if the fan starts at a time when there is no heat in a radiator, the water of condensation may be frozen which might result and sometimes does result in cracking of the radiator. Also under these conditions, when thawing takes place, a considerable amount of damage may be done by leaking water.

The main object of the invention is to provide means which will obtain and allow operation of the fan, as the result of temperature fluctuations in a roomonl when the heater has reached a predetermined temperature. Another object of the invention is to provide a very simple electrically operable means for controlling the operation of the fan. Another and more specific object is to provide a single relay, operable and controllable through two devices, one dominating control of the other, one a thermostatically responsive device arranged in the room, and the other a device responsive to fluctuations in heat supply at the heater. The arrangement is such that the room device can only operate to cause energization of the fan motor when both heater and room devices are closed.

will not start unless the room device is fully closed. v

Features of the invention include the broad idea of controlling the fan of a unit heater by use of a single switch controlling, or relay device, to positively prevent running of the fan when the heater is cold, along with the detailed arrangement of the elements of the apparatus for obtaining the results set forth herein. I

The figure of the drawing diagrammatical- 1y represents the system, with motor not runnlng.

To show one application of the invention the following construction is illustrated:

The fan motor is indicated at 1 and this motor is opposingly arranged in such relation to a radiator 13" as to circulate air heated by the heater. In this instance, a circuit is provided which includes a transformer the primary coil of which is indicated at 2 and the secondary coil of'which is indicated at 3. A single relay is used and has an armature 11 having a contact 6 cooperable with contact 5 of the high voltage circuit. Conductor 7 con nects one side of the motor 1 with one side of the main line 25, and conductor 8 connects at the opposite side of the motor with the contact 5, the opposite side 26 of the main line is connected by conductor 9 with the contact 6 of the armature 11. The relay coil is indicated at 10 and is connected with one side of the secondary 3 by conductor 15. The armature 11 is provided with a contact 12 cooperable with contact 13. A thermostatically responsive room device has a movable member 1' having inthis instance two electrically connected elements, respectively 1" and 1' respectively engageable with two contacts 6-10. These elements 1"'r are sequentially engageable with the contacts b w. Element 7 is first to engage and last to-disengage, and

element 1" is last to engage and first to disenf her 21, which member in this instance has a pair of elements insulated from one another, and respectively designated R and R. These elements are engageable respectively with contacts B-W, and make sequentiallyR' first and R lastand in reverse order when breaking.

The coil 10 and contact 12 are connected by conductor 17 to contact B of the radiator device. The opposite side of the secondary side of the transformer 8 is connected by conductor 16 with contact lV ot the radiator device. Contact 13 is connected by conductor 18 with member 7 of the room device. It will be noted that the elements 1, 1 are not insulated. Contact 5 of the room device is connected by conductor 19 with element R of the radiator device, and contact w of the room device is connected by conductor 20 with the element R of the radiator device.

The connections in the secondary circuit are so arranged between the room and the heater device of the relay, that the room device can only operate to close the relay and obtain energization of the fan motor, when both elements are making with respective contacts Z w, and this energization can only take place when both elements of the radiator device are engaging respectively With the contacts B-lV of that device. It will be further noted that one element (7 and R) of each device acts to maintain a closed circuit for the holding contact 1213.

It will be understood that the element 1" of the room device can be of a bimetallic structure, or of any structure which will make it responsive to bend in opposite directions following the fluctuations in temperature. It will be further understood that the element 21 may be either a bimetallic element or a Bourdon tube or other device which can be afi'ected when the radiator is hot to move in one direction and when the radiator is cooled to move in the opposite direction.

Operation The diagram shows the system inoperative, with both room and radiator devices having their elements out of contact. In this position, therefore, the fan is not running because the radiator is sufiiciently cool to have caused breaking at both contacts, and the room thermostat is sufficiently warm to have also opened or broken both its contacts.

To show how the device operates to prevent energization of the fan motor when the heater is cold, let it be assumed, with the device positioned as shown in the illustration, that the room device cools sufiiciently to make at 1"-w. Under these conditions, the coil 10 cannot be energized to close the motor control switch because the elements RR are both spaced away from their contacts. Let us suppose that, on continued cooling of the room thermostat, the element 7 contacts I).

It is evident that no circuit can pass through the conductor 19, element B because R-B are out of contact. Let it be supposed that while 1 w and 7b are together, the radiator device heats sufiiciently to make at R\V. Even under these conditions no current can pass (conductor 20, R, V, 16, 3, 15, 10, 17 to B) because RB are not making. Nor can current pass 19K for the same reason. lVhenever RB make, however, coil 10 is energized, motor control switch closes and the fan motor starts. Simultaneously holding contact 1213 closes and the circuit for maintaining this contact closed includes elements r R-. If when the fan is thus running either the room thermostat or the radiator device would move away from their contacts sufliciently to break either at rb or at R-B, or at both simultaneously or either one before the other, the elements 7' R will still maintain the circuit in closed position and the fan will continue to run. Immediately, however, that either 1 or R break, either simultaneously or one before or after the other, the coil 10 will be de-energized and the switch 11 opened to stop the motor.

It will thus be seen that the radiator device dominates the control, to the extent that no control whatever can be had through the room device unless the radiator device is making at both contacts BW'. It will, however, be seen that if the relay circuit has been once closed, one of the contacts of each device may open and the circuit still be maintained in closed condition providing that one element of each device is making.

The construction and Wiring arrangement herein is such that an electrically operable device, such as a relay or its equivalent, can never be energized unless all contacts of the control devices are clean and can make electrical contact, as distinguished from a mechanical contact by a dirty contact element, in which latter case no current can pass. As a result, the device provides means whereby if there is not the proper electrical contact, the device cannot be operated at all, and this is a valuable feature of the invention. Another feature is that, holding contacts are supplied and the arrangement is such that if both contacts of one of the devices are electrically engaged and only the holding contact of the other device is engaged and the device is approaching contact position, and if a vibratory movement causes the element to engage its contact prematurely to energize the relay or equivalent device, after such engagement and therefore after energization of the electrically operable device de energization cannot take place although the last contact to make vibrates considerably before it makes its normal contact. Means is thus provided whereby vibratory disturbance cannot cause the electrically operable device to be (lo-energized, unless by the natural thermostatic action to break the contacts.

This holding Assume both contacts of the room thermostat to be closed and assume the radiator device to be warming. Su pose contact R makes and conditions the olding circuit to be held closed after the closing of the relay. Then assume R to be near but not yet touch: ing its contact. Then suppose some sufiicient violent vibration which will cause the contact R to touch its contact before the radiator device is suflicientlv hot to cause the contact to be made naturally. Inasmuch as a holding contact is provided if this radiator device is closed by vibration, the circuit to the relay will be closed and the relay will remain closed. Therefore, except for the holding circuit, the relay would close on the first tap of the contact R', then open, then close again and so on continually in a vibratory manner responsive to the outside vibratory disturbance. contact arrangement is possible because the olding. and making circuits pass through the radiator device without any intercommunication. The insulation of the two sequentially making contacts obtains. this an ti-vibratory control or makes such a control possible, whereby two devices can be used, either being able to cause the relay-to open, but wherein both must cooperate to obtain closure.

Therefore in the present device, in case one of the contacts isdirty no current can pass to the electrically operable device, no matter how many other contacts are electrically making, and after energization of the relay due to an electricclosu're, energization is maintained if one of those contacts which was first to close remains closed.

I claim as my invention: .1. A pair of thermostatically responsive devices, a relay and source of power in circuit with said devices, each device having two contacts, and a movable member having portions sequentially engageable with said contacts in one order and disen'gageable in reverse order, and circuit connections such that energization of the relay can only be obtained when all contact elements of both devices are electrically closed, and the arrangement further being such that after'energization of the relay, due to this closure, energization is maintained,

. if those portions of the movable member of each device whicha were first to close remain closed.

device in which the contact portions are insulated from one another.

3. A motor and circuit therefor including a switch, means electrically energizable for o eratin the switch, thermostatic switch dethermostatic switch devices, motor line switch operating means, and holdingcontact, such that all contacts of the pair of switch devices must be electrically closed to obtain energization of said motorv switch operating means. 1

4. A motor and circuit therefor including a switch, means electrically energizable for operating the switch, thermostatic switch devices each having two contacts and a movable member having portions sequentially engageable with the contacts in one order and disengageable therefrom in a reverse order, the contact-engaging portions of one of the switch devices being insulated from one another,"a holding contact arranged to close when the motor line switch operating means is energized, and electrical connections between the contact, movable elements of the thermostatic switch devices, motor line switch operating means, and holding contact, such that all contacts of the pair of switch devices must initiallyelectrically close to obtain energization ofsaid motor switch operating means, and such that as long as at least one contact of each of the said thermostatic switch devices is electrically closed such energization is maintained.

5. A motor and circuit therefor including a switch, means electrically energizable for operating the switch, thermostatic switch devices each having two contacts and a movable member having portions sequentially engageable therewith in one order and disengageable therefrom in a reverse order, the engaging portions of one of the movable members being insulated from one another, a holding contact arranged to close when the motor line switch operating means is energized, and electrical connections between the contacts 'and movable elements of the thermostatic switch devices, motor line switch operating means, and holding contact, such that all contacts of the pair of switch devices must ini tially electricatly close to obtain energization of said motor switch operating means, and such that, as long as at least one contact of each of the said thermostatic switch devices is electrically engaged such energization is maintained, and said holding contact being in series with one contact of each thermostatic switch device.

6. An electrically energizable switch operating means, thermostatic switch devices each having two contacts and a movable member having portions sequentially engageable therewith in one order and disengageable therefrom in a reverse order, the contactengaging portions of only one of the switch devices being insulated from one another, a holding contact arranged to close when the switch operating means is energized, and electrical connections between the contacts and movable elements of the thermostatic switch devices, switch operating means, and holding contact, such that all contacts of the pair of switch devices must initially electrically close to obtain energization of said electrically energizable switch operating means.

7. A motor and circuit therefor including a switch, and electrically energizable switch operating means, thermostatic devices each having two contacts and a movable member having portions sequentially engageable therewith in one order, and disengageable therefrom in reverse order, a holding contact arranged to close when the switch operating means is energized, and electrical connections between the contacts and movable elements of the thermostatic switch device, switch operating means, and holding contact, such that after electrical closure of all but one of the contacts of the thermostatic switch devices, a mechanical vibratory disturbance of that movable member which does not have its contactengaged, to cause it to alternately engage and disengage its contact, will not cause deenergization of said electrically energizable switch operating means.

In witness whereof, I have hereunto set my hand this 20th day of October, 1928.

HAROLD W. SWEATT.

Images