US2266563A - Heating system - Google Patents

Description

Dec. 16, 1941. D. H. MCC RKLE 2,266,563

HEATING SYSTEM Filed Aug. 19, 1939 47 1 {l 45 U I M M. /.9 44 4 @A p .Zzaemor Patented Dec. 16, 1941 HEATING SYSTEM Donald H. McCorkle, Berkeley, Calif.

Application August 19, 1939, Serial No. 291,024

7 Claims.

This invention, a heating system, consists of a new and improved method of establishing and maintaining a uniform room temperature devoid of thermal stratification, and relates in particular to a new method of thermostatically controlling the operation of warm-air furnaces, particularly those which are provided with forced draft heat distributing and circulating means.

Warm air furnaces are now being quite genwhich opens and closes a fuel valve for feeding the furnace, in accordance with the heat demands of the room in which the room thermostat is located. The fan or blower introducing the forced draft is thermostatically controlled by the relative heat within the furnace casing, and so arranged that when the temperature within the casing has reached a predetermined value, the fan is automatically started and continues to operate until the temperature within the casing drops below the starting value, at which time operation of the fan or blower is terminated.

With this type of forced draft control, the fan operates intermittently with full capacity cycles of short duration, resulting in a series of on-andoil operating cycles, producing alternatelyoverheated and underheated conditions of. the" rooms heated by the furnace. In addition, this method of operation results in such short periods of circulation that the warm and cold air in the rooms does not become completely mixed, and thermal stratification ofthe warm and cold portions of the air immediately takes place each time the fan stops, resulting in cold floorsand the condition commonly termed cold seventy."

It is a well-recognized fact that in forceddraft warm air systems great advantage can be gained if the fan can be made to operate at increased periods of time. However, with register outlet velocities as generally created, air must be heated to approximately 100 F. to avoid discomfort, therefore under the conditions just described, extended operation of the fan is impractical and unsatisfactory.

There are several methods current for obtaining longer cycles of fan operations, included in which is a two-stage thermostat designed to operate a high-low burner; and an outdoor thermostat used in conjunction with the regular type of roomthermostat to modulate the burner capacity. Both systems lack in eificiency, precision and uniformity and therefore incur serious objections, and do not attain the desired result.

With my system I propose to so control the furnace fire that the heat will be delivered in accordance with requirements, and in such manher that the fan will continue to operate for far greater periods of time for each cycle, and to so control the heat within the furnace through.

interdependent, cooperative and selective control through existent room, duct, and furnace temperatures,' that the room temperature will be maintained substantially uniform and free of thermal stratification.

The objects and advantages of this invention are as follows z, I

First; to provide a heating system which will maintain a substantially uniform room temperature, with the room free of thermal stratification.

Second; to provide a control system for furnaces which will increase the operating time of each cycle of operations over that of the usual operating cycle.

Third; to provide a control system which will materially reduce the differential in room temperatures between warm and cold stages.

Fourth; to provide a 'control system which will automatically regulate the duct temperatures in accordance with the demand for heat.

Fifth; to provide a system which will automatically regulate ,the register outlet temperatures in conformity with heat demands.

Sixth; to provide an automatic control which will maintain the outlet temperatures below a predetermined value irrespective of variations in the volume of air flowing through the furnace.

Seventh; to provide a heating system which will cause delivery of air which is heated to varying temperatures proportionate to the demand delivery and delivering no heat when a defined room temperature exists, and delivering low heat for low temperature differentials and high heat with higher temperature differentials as related to a maximum. normal temperature.

Eighth; toprovide a system in which the fuel supply to the furnace is controlled to initiate heating at full capacity and to reduce the capacity as heating progresses and proportionate to the demand for heat.

In decribing theinvention reference will be made to the accompanying drawing, which is a diagrammatic view of a warm-air furnace with an associated wiring diagram illustrating the 'rneeonvencemi warm air furnace includes a furnace casing l having a duct H which has branches connecting to various registers in the rooms to be heated, and which branches and registers are well known and require therefore neither description nor illustration. In addition, a burner l2 has a fuel connection l3 which is provided with a suitable fuel control,

In this invention the controls can be readily formed into a single unit, but which are here illustrated as consisting of separate controls. Two of these controls; l4 and Hi, are preferably of the time-delay-opening type described in my Patent Number 2,118,443, granted May 24, 1938, for Electric valve; and the third control consists of a bypass l6 controlled by a suitable valve H which controls the amount of fluid delivered to the control l4, and is therefore an associated element thereof. This bypass can be arranged according to known means in which the valve in the control I5 is prevented from fully closing and thereby functioning as the bypass, displacing|6 and-H. I

Both controls l4 and I! are adapted to pass a full supply -of fuel in series from the fuel supply line EB'tothe fuel connection l3, but the control M is limited to the amount passing through the adjusted valve "IT or its equivalent in the" control Hi When the control i5 is closed, therefore the amount of fuel reaching'the burner is dependent upon whether both controls are open, whether control I5 is closed, and whether control I4 is closed, and creatingrespectively high, low, and no fire.

These controls are of the conventional type suited to the particular type of fuel used, and in which'an electrically-heated thermostat or an electromagnet controls the opening and closing of a valve for controlling admission and passage of fuel to the burner H, the structures being well known in the art and therefore not illustrated in detail.

The conventional forced draft type warm air furnace also includes a blower or-fan l9 driven by a motor for forcing the heated air through the furnace casing to the registers previously mentioned. The motor 20 is controlled by a thermostatic control switch or relay 2| which is controlled by the heat within the casing and starts operation of the motor and its associated fan as soon as the temperature within the casing rises ,to a, predetermined value, and discontinues operation when the temperature drops back to a point below said predetermined value, and this motor and control are connected to the main source of potential 22, 23 through wires 24, 25 and 26.

' A suitable thermostatic control 21 is associated with the furnace casing and controlled by the heat therein, and is preferably of a type similar -to that illustrated and described in my copending application Serial Number 241,808, filed November 22, 1938, now Patent Number 2,227,732, dated January 7, 1941, for Thermally-controlled switch, and a second control of similar or suitable type is associated with either the main duct or'with a branch thereof, and is indicated at 28 as associated with the main duct, and it is 'controlled by the heat within the duct with which it is associated. A third control 29 which is of the double or two-step control of room thermostat, has two bimetal elements 30 and 3| which respectively form circuit control devices in combination with the respective contacts 32 and 33. These elements have a common connection 34 to one side 35 of the secondary of a low voltage transformer 36, and the two contacts 32 and 33 are respectively connected through the respective wires 31 and 38 to one side each of the respective fuel flow controls l5 and I4.

The other side of each of the two controls I5 and H are respectively connected through wires 39 and "to one side of the control 21 the other side of which is connected through a wire 4| to the other side of the secondary of the transformer 36 the primary of which is connected to the source of potential 22, 23.

The control 28 has one side connectedthrough a wire 42 to contact 33 and the other side is connected through a wire 43 to the one side 4d of the control I5. A switch 45 is provided for manual control of all of the circuits.

The operation of the system is as follows: The element 30 and its contact 33 forms the high temperature side of the room thermostat and is adjusted to break contact at a predetermined room temperature, usually F., while the element 3| with its contact 32 forms the minimum temperature side and breaks contact at a slightly lower temperature, about 69". Switch 45 is closed the room temperature drops to 69 or to that for which the element 3| is adjusted and the circuit is thereby closed from the secondary of the transformer 36 through wire 34- and switch 45, element 3|, contact 32, wirefil to one side 44 of the high-flow control 85, and thence from the other side 46, wire 39, wire 40 to control 21, and thence through wire 4| to the other side of the secondary of the transformer, control 21 being closed, since the furnace is cold.

A second circuit is completed from the secondary of the transformer through wire 34, switch 45, element 30, contact 33, wire 38 to one side 4'! of fuel control 4, thence from the other side 48 through wire 40 to the control 21 to wire 4|.

A third circuit is completed through wire 42 to control 28, thence through wire 43 to the one side 44 of the fuel control l5 and thence through wires 39 and 40 to the secondary of the trans.- former.

Closing. of all circuits opens both fuel controls l4 and I5 and admits fuel through connection i3 to the burner |2 at full capacity, and heating of the furnace is started.

As soonas heatinghas progressed to a predetermined degree, the control 2| closes a circuit from power line 23 through wire 25, control 2|, Wire 24, motor 20, wire 26 to the other power line 22, starting the fan, which forces the heated air within the furnace casing out through the duct andwhen the heat within the furnace casing reaches a predetermined value, the circuit is broken to both fuel controls closing off the burner l2, the fan continuing to oper-. ate, and thus the temperature within the casing is controlled.

aaoaoea predetermined minimum temperature, element combination, controlfl functioning only to completely shut off the fuel supply in the event of excessive casing heat.

As the room temperature rises to the maximum point, contact is broken at 30, 33, breaking allof the circuits with the exception of the fan circuit, and closing both fuel controls It and [5, and after the heat within the casing drops to a predetermined value the circuit to the fan motor is broken and circulation ceases, except as to thermal influence of the heat within the casing and ducts.

The condition. described would rarely be attained, since with this system, as soon as the slightest drop occurred in temperature below the maximum, the circuit will be recompleted through .element 30 and contact 33 to the-control ll, further controlled by the control 28 in the duct, thus uniform room temperature is maintained.

If sufllcient heat is not provided by this arrangement, to maintain the room temperature above the minimum, the first circuit will be again completed through element 3| and contact 32 to the high fire side of the fuel delivery control.

Thus there are three circuits in parallel, each dependent upon the other, each cooperating with the other, and each being selective in conformity with temperature conditions and the demand for heat.

Thus the fan is operatedcontinuously over considerable periods of time due to the extreme flexibility of'the control and precisionmaintenance of temperatures, thus preventing thermal stratification in the room due to more constant fan operation.

It will be understood that variations in the method and in the construction and arrangement of parts, which variations are consistent with the appended claims may be resorted to without detracting from the spirit or scope of the invention, or sacrificing any of the advantages thereof.

I claim: I

1. A heating system comprising a furnace having a casing and a duct; a fuel supply line; a fan and driving means and control means for said driving means and controlled by the heat within the casing; a first fuel control and a second fuel control connected in series in said fuel line and a by-pass about said first fuel control and means for manually adjusting the passage for fuel through said by-pass for delivering a predetermined restricted amount of fuel through said second fuel control; thermostatic control means controlled by the heat in said casing and controlling said first and second fuel controls for terminating delivery of fuel under excess heat conditions in said casing; thermostatic control means controlled by the heat in said duct and controlling said first fuel control for terminatfor controlled respectively by established maximum and minimum room temperatures and controlling both of said fuel controls for maximum delivery of fuel through both controls under room temperatures below said minimum vand for restricted delivery when the room temperature exists between said maximum and minimum when the heat in said duct is at a predetermined maxi mum and for termination of fuel delivery when room temperatures attain said maximum temperature.

2. A heating system comprising a furnace having a casing, a duct; 9, fuel line and a fuel control means in said fuel line for selectively gauging delivery of fuel in varying amounts and for termination of delivery: first control means associated with said casing and controlled by the heat therein and controlling said fuel control means to terminate delivery of fuel in the event of existent abnormal heat conditions in said casing; second control means associated with said duct controlling said fuel control for delivery of fuel in restricted amount in the event of abnormal heat conditions in said duct and for delivery in maximum amountunder subnormal heat conditions in said duct; and third control means controlled by existent room temperatures and elec trically associated with said fuel control and with saidfirst andsecond controls and controlling delivery of fuel selectively for maximum delivery of fuel below a predetermined minimum room temperature, alternate restricted and maximum delivery under control of said second control under temperatures between said predetermined minimum and a predetermined maximum, and

termination of delivery when said room temperaing delivery of fuel through said first control for delivery of fuel only through said second control in restricted amount under excess temperature conditions in said duct; and a room therfecting a substantially uniform continuous room temperature within the limits of minimum and maximum temperatures.

3. A heating system comprising a furnace having a casing, a duct, afuel line; a first thermostatic switch operable to open under the infiu- -ence of heatin said casing; a second thermostatic switch operable under the influence of heat within said duct; a room thermostat including a first switch and a second switch both of which are closed when the room temperature is below an established minimum and sequentially opened in response to successive rises in room tempera minationof delivery, and three circuits in parallel including respectively; said first switch, said fuel control for low delivery of fuel and said first thermostatic switch; said first switch, said second thermostatic switch, said fuel control for high fuel delivery, and said second thermostatic switch; and, said second switch, said fuel control for high delivery of fuel, and said first thermostatic switch, whereby when the existent room temperature is below the established minimum, high fuel delivery is provided without control by the duct temperature, and when the existent room temperature is between the established minimum and maximum, high and low fuel delivery are alternated through control by the duct temperature for maintaining a substantially constant duct temperature, and when the existent room temperature is at or above its established consisting in maintaining a cold furnace when mostat having Contacts and circuits h 78 there is no demand for heat by a space, operatin the furnace when the space temperature drops below a predetermined maximum, under control of the duct temperature, with high fire when the duct temperature is below'a predetermined value, and low fire when the duct temperature reaches said predetermined value, to maintain a substantially constant temperature in the duct while the space temperature is between said predetermined maximum and a predetermined minimum; operating the furnace under high fire without influence by the duct temperature when the space temperature drops below said predetermined minimum; reverting to alternate high and low fire under control of the duct temperature as previously recited when the space temperature rises above said predetermined minimum, and discontinuing all fire other than the pilot when either the space temperature reaches said predetermined maximum, or when the casing temperature attains a predetermined maximum.

5. A furnace control comprising; a room thermostat, a duct thermostat, and a casing thermostat; a fuel line and selective control means for high and low delivery of fuel therefrom and for termination of delivery of fuel; a source of potential; a first circuit including said source of potential, said room thermostat, said selective control means for low delivery of fuel, and said casing thermostat; and a second circuit including said source of potential, said room thermostat, said duct thermostat, said selective control means for high delivery of fuel, and said casing thermostat; said thermostats respectively breaking circuits at established difierent temperatures; said room thermostat completing the circuits when the room temperature drops below an ing said second circuit to interrupt high delivery breaking all circuits when said room temperature reaches its established maximum.

6. A structure as defined in claim 5; said room thermostat having two circuit control means operable sequentially with successive increases or decreases in temperature, said first and second circuits being controlled by one of said circuit control means; and a third circuit including the other of said circuit control means, said fuel control for high delivery of fuel, said casing thermostat, and said source of potential; whereby high delivery of fuel is established and maintained by said third circuit uninfiuenced by said duct thermostat or by the other circuits when said third circuit is completed through a recession in the room temperature below an established minimum and being interrupted to transfer control to the other circuits and the duct thermostat when said minimum is attained through a rise in room temperature.

7. A furnace control comprising; a source of potential and first, second, and third circuits; a space thermostat having first and second circuitcontrol means connected in parallel to said source of potential; said first circuit-control means operating to close said first and second circuits when the temperature of the space drops below an established maximum; said second circuit-control means operating to close said third circuit when the temperature of the space drops below an established minimum: a duct thermostat included in, and operating to open said first

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