CA1183237A - Integrated control system using a microprocessor - Google Patents

Integrated control system using a microprocessor

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Publication number
CA1183237A
CA1183237A CA 388139 CA388139A CA1183237A CA 1183237 A CA1183237 A CA 1183237A CA 388139 CA388139 CA 388139 CA 388139 A CA388139 A CA 388139A CA 1183237 A CA1183237 A CA 1183237A
Authority
CA
Grant status
Grant
Patent type
Prior art keywords
means
burner
fuel
gas
air
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA 388139
Other languages
French (fr)
Inventor
Ralph H. Torborg
Ulrich Bonne
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Honeywell Inc
Original Assignee
Honeywell Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

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Abstract

ABSTRACT OF THE DISCLOSURE
An integrated control system for a temperature conditioning apparatus which contains a microprocessor which is connected to the various components of a control system of the temperature conditioning apparatus such as the space thermostat, the fuel valve, the fuel ignitor and ignition proving apparatus, the plenum temperature sensor, the induced draft blower motor, refrigeration compressor and coil temperature sensor, and the air circulating fan. With the microprocessor, which has the capability of fast and many types of operations, the interaction of parameters of the temperature conditioning apparatus and operation of the various components of the system can be controlled in an improved manner to add to the overall efficiency of such a temperature conditioning apparatus.

Description

INTEGRATED CONTROL SYSTEM USING ~ MICROPROCESSOR

BACKGROUND OF THE INVENTION

Even though prior art heating and cooling apparatuses had fuel valve controls, plenum air temperature sensors, air circulatin~ fans, induced draft blowers for the exhaust gases of a furnace, ignition and flame sensor appaxatus for proving that the ignition of the fuel in the burner takes place, and many other parameter sensors, all of which were 10 a part of a control system or a furnace or ai.r conditioning .~
co~pressor supplying heated or cooled air to a space in wnlch a thermostat was contained, there has ~een a continual need fo.r improvement in such control systems. With the advent of increased ener~y costs, an even greater demand has been s~own for more efficient heating and cooling appaxatuses and sy,stems, especially for homes and dwellings wherein an individual :Eurnace and air conditioning system suppli.es the heated or cooled air to the home as required.by a space thermostat.
Coincidental with the increased cost of energy, the advent of low cos~ microprocessors has made it possible for the gathering of parameter data and the control of various components of a control system in many new manners which provide the long-awaited increased efficiency and thus cost saving in the operation of a furnace and air conditioning apparatus~

SUMMARY OF THE PRESENT INVENTION

The present invention is concerned with the prevention or reduction in the amount of flame "roll out" and thus to provide a longer time to prove the ignition of a gas flame.

By the operation of the induced draft blower durin~ the initial start up of the furn~ce at a high speed and the operation of the gas valve at a low fuel flow stage, the air to fuel ratio is maintained high during the ignition period of the fuel to avoid the roll out condition. After flame is proven, the gas flow can be at a high rate for the initial heating of the furnace to prevent rusting due to condensation and then a reduction of the fuel flow to low fire with a low induced draft blower speed for regular operation.
In accordance with the present invention there is provided an improvement :in a control system for a furnace having a multispeed induced draft blower, a multistage gas control valve means for furnishing gas to a burner with a predetermined air to fuel ratio, and a gas ignition apparatus, the improvement comprising, means, upon the starting of an operation of the furnace, for energizing said induced draft blower at a speed to provide a large amount of air to the combustion chamber of the furnace and for energizing said gas valve for providing a low gas flow into said combustion chamber so that the air -to gas ratio .is higher than normally maintained so that upon said means energizing said gas ignition apparatus to ignite the gas of the burner, the gas in the combustion chamber is not ignited and "roll out" of the combustion flame is minimized even after long ignition delays.
In accordance with the present invention there is further provided in a method of controlling the operation of a gas fired furnace having an induced draft blower for inducing the air flow into the combustion chamber and out through an exhaust stack at various rates and a fuel valve for admitting fuel to a~ burner in the combustion chamber at a low rate and ~3f~37 a high rate ha~ing the following steps upon the call for operation of the furnace by a space temperature responsive means, energizing the induced draft blower means at a high rate to provide an excessive amount of air into the combustion chamber, energizing the gas valve furnishing gas to the burner at a low fuel flow rate whereby a normal air to fuel ratio e~ists at the burner and a high air to fuel ratio exists in the combustion chamber downstream of the burner, igniting the fuel at the burner wherein a normal air to fuel ratio exists, sensing the presence of a flame and thus the combustion of the fuel in the combustion chamber, and upon the presence of combustlon, operat-ing the blower means at its low rate.
Brief Description of the Drawings The invention is shown in the enclosed drawings of which:
Figure 1 is a schematic showing of a conventional forced air heating and cooling system~
Figure 2A to 2D (~our) disclose the circuit diagram of a control module connecting the various components of the system to a microprocessor to provide the integrated control system.
E'igure 3 is a composite of Figures 2A to 2D.
Description of the Preferred Embodiment of the Invention _ Referring to Figure 1, a conventional temperature con-ditioning apparatus or furnace 10 is shown. The furnace receives fuel to a burner 9 from a gas source connected to pipe 11 and the fuel supply is controlled by a gas valve 12. The air to fuel ratio of the burner is normally fi~ed by the manufacturer's design. Gas valve 12 of a variable capacity may be of several types such as the VR854 for two s-tage direct spark con-trol and the VR852 for two stage intermitteni pilot control, both made and s~ld by Honeywell ~nc. and shown in brochure 60-2447-2 of May 1980. The gas is ignited and a - 2a -~3~
flame is sensed by a conventional igniter and flame sPnsor 13 such as the Q354 made and sold by Honeywell Inc. and sho~rn in brochure 60~2053-8 of July 1980. The e~haust gases from the furnace combustion chamber 81 downstream of burner 9 are forced out of a stack 14 by a blower 15 to provide an induced draft blower (IDBI furnace. Blower 15 is driven by a conventional shaded pole 120 volt A.C. motor having a Hall effect sensor mounted on the motor shaft to provide a pulse each revolution for a speed sensor and control circuit.
The temperature in the bonnet or plenum is sensed by a temperature responsive element 20 such as a C800 Platinum resinate sensor made and sold by Honeywell Inc. and shown in brochure 60-2484-1, Nov. 1979. Temperature condl~ioned rnedium or air is circulated through the plen~m from a return . .. .
duct to the space 21 by blower 22 in a conventior,al manner or by a circulator sump for a hydronic system. The temperature responsive element or thermostat 23 such as a T87F thermostat made by ~oneywell Inc. is located in the space connected to controls fox the furnace. A conventional refrigeration compressor or heat pump 26 has an outdoor heat exchanger or coil 27 and an indoor heat exchanger or coil 28. A fan driven by motor 29 removes heat from coil 27. Coil 28 is in the furnace plenum to deliver cool air during the air conditioning operation. Coils 27 and 28 have temperature sensors 36 and 37, respectively, of the C800 type. An integrated system control module 24 which is supplied with power from a transformer 25 connected to a source of power 30, has all of the mentioned apparatus connected thereto for controlling the furnace and compressor.

Referring to Figure 2, which is made up of ~ composite of Figures 2A to 2D, the schematic circuit of the integrated system control module 24 is shown in more detail. In Figure 2A, transformer 25, which is connected to the power source 30, supplies power to a conventional power supply 40 which has one output 41 connected to a timing signal generator 42, in Figur~
2D, which provides a 60 Hz signal available over conductor 43.
A thermostat 23 is connected over the six wire conductor 44 to the module 24.
The module 24 has a microprocessor 45 of a conventional type known as the 8049 microprocessor which is made and sold by several different companies such as Intel, National Semi Conductor, and Nippon Electric Company. The microprocessor which is shown in Figures 2C and 2D is programmed as shown in Appendix II. The microprocessor receives the signal from the timing signal generator 42 over conductor 43 at pin P14 shown in Figure 2E. Similarly, the output of the thermostat 23 is connected through switching circuit 50 over the input conductors 51 to the microprocessor at pins P10, Pll and P12.
The induced draft blower 15 has two connections to the control module 24 (see Figure 1). A first connection 52 is from the motor speed sensor in the blower which comprises a conventional Hall effect transducer for providing a pulse on each revolution of the motor shaft and thus providing a revolutions per minuke (rpm) signal or input 52. Two other colmections 53 and 54 which are shown in Figure 2G connect motor speed con-trol 55 of the control module to the induced draft blower motor. The motor speed control receives a signal over the conductor 60 from pin P26 of microprocessor 45.

Re~erri.ng to Figure 2B, an input is provided at 61 for a conventional analyzer which would be connected to a buffer 80 to the microprocessor for analyzing the operation of the system. Input circuit 62 connects plenum temperature responsive element or sensor 20. Input 63 connects a temperature responsive element or sensor 36 which senses the temperature of an air conditioning discharge coil when the refrigeration system is used. Input 64 connects temperature responsive element or sensor 37 from the indoor coil when the air conditioning system is used. Connection 65 is a common connection for many of the input circuits.
These sensors, that is the plenum sensor 20, air conditioning discharge sensor 36, air conditioning indoor coil sensor 37, are all connected to a conventional CMOS
multiplexer 69 (see Figure 2B) which provides an output over conductor 71 to a conventional analogue to digital dual slope con~erter 72 providing the input to terminals Tl and ALE of the microprocessor over conductors 72 of Figure 2D.
An optional selection circuit 73 is shown on Figure 2s which provides for different arrangements of the circuit to the multiplexer in accordance with a selection table I as Appendix I. The optional selection can be accomplished by making different circuit connections either by breaking jumpers or using conventional pins to make selected connections.
Referring to Figure 2C, a shift register 80 has an output at 81 connected to a safety switch r~lay 82 and Kl.
Referring to Figure 2D, input 90 provides the connection from the flame igniter and flame sensor 13 and is connected to the flame sensor circuit 91 of the type S825C made and sold by ~loneywell Inc. and shown in brochure 60-2053-8 of July 1980 for providing a xedundant signal over conductors 92 to the pins Pl3 and Pl5 of the microprocessor. Inputs 93, 94 and 95 are connected to the gas valve 12 and provide fox a control of the pilot valve and main valve (a multi or t~o stage control) S and high fire valve (see Figure 2I) when two stage burner operation is used. Output lOl and 102 for low speed and high speed operation are connected to a circulator for a hydronic system or circulation fan 22, Output 103 is connected to the ignitex 130 The ou~.put of the microprocessor from conductors 104 are eonnected to control a plurality of relays-K2, K3, K4~ KS and K6, which have associated contacts wi~h similar labels for controlling the various components connected to output circuits 94~ 95, lO0, lOl, 102 and 103.
-OPERATION OE' THE PREFERRE~D EMBO~IMENT OF THE INVEl\lTI~I
1 5 ~
Referring,to-Figure 1, when the space thermostat 23---calls for operation of the furnace, the induced draft blower 15 and the yas valve 12 are energized. With the normal fuel to air ratio, such a furnace is normally te~ted by Underwriters Laboratory to ensure that ignition of the burner takes place before the accumulation of gas is sufficient that the "roll out" of the burner occurs. "Roll out" is a result of the flame moving outside of the combustion chamber when a large accumulation of air and gas mixture downstream of the burner ignites. To ensure that such "rol] out" doesn't take ,place, especially where a longer time for ignition and the proving of the existence of a flame is desired, the blower is operated at a high speed to have an over abundance of air and the valve 12 is energized at a low fuel flow or first stage.
A normal (premixed) air to fuel ratio exists at the bu~ner by design 9; with excessive air ¢yreater than 100~ pro~ided by the induced draft blower, downstream of the burner in the combustion chamber 81, a high air to fuel ratio e~ists.
Ignition of the gas at the burner takes place in a normal manner, but since the air to fuel ratio downstrearn of the burner is high, the gas in that area does not ignite and "roll out" does not occur even after excessive ignition delays. Such lends itsel to direct ignition of the burner.
The accumulatlon of gas in the combustion chamber is then ~0 limited and with the excessive air, when ignition does take place, "roll out" of the flame is a minimum.
As soon as the flame proving apparatus 13 senses the presence of combustion, the speed of the induced draft blower: i.s left at high speed and the gas valve is operated at high fire ~second stage~ to ensure that the combustion chamber heats up as-fast as possi~le to minimize r~sting of the furnace by removing moisture from the furnace which is condensed by combustion products at the beginning of the combustion operation. After some predetermined time such as ninety seconds, when the combustion chamber is up to temperature, the gas valve 12 would be returned to the first stage of operation, or low fire, and the blower speed is reduced to its corresponding low speed (first stage of operation) to enhance efficiency.

Claims (22)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR RIGHT IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An improvement in a control system for a furnace having a multispeed induced draft blower, a multistage gas control valve means for furnishing gas to a burner with a predetermined air to fuel ratio, and a gas ignition apparatus, the improvement comprising, means, upon the starting of an operation of the furnace, for energizing said induced draft blower at a speed to provide a large amount of air to the combustion chamber of the furnace and for energizing said gas valve for providing a low gas flow into said combustion chamber so that the air to gas ratio is higher than normally maintained so that upon said means energizing said gas ignition apparatus to ignite the gas of the burner, the gas in the combustion chamber is not ignited and "roll out" of the combustion flame is minimized even after long ignition delays.
2. In a furnace control system having a fuel burner with a normal amount of premixed air and fuel comprising an induced draft blower means adapted to be connected between the combustion chamber of a furnace and an exhaust stack, said blower means having at least two speeds, fuel control means adapted to control the supply of fuel to a burner in the combustion chamber of the furnace, temperature responsive control means adapted to respond to the temperature of a space to which heated medium is being delivered by the furnace, ignition means adapted to be mounted in the combustion chamber, and first means connecting said temperature responsive control means to energize said induced draft blower means, said ignition means, and said fuel control means whereby said blower means is operated at a predetermined high speed to provide excessive air to the combustion chamber to maintain a high air to fuel ratio in the combustion chamber downstream of the burner during ignition of the fuel whereby ignition of the fuel takes place at the burner and not in the combustion chamber downstream of the burner.
3. The invention of claim 2 adapted for use in a gas furnace wherein the air to gas ratio is high to avoid the "roll out" condition upon ignition of the gas only at the burner and therefore allows more time to prove the existence of a burner flame ignition.
4. The invention of claim 3 wherein a high air to gas ratio is made with 100 percent excessive air.
5. The invention of claim 3 wherein said fuel control means is a gas control with a high and low fire rate, and comprising, timer means, flame proving means, and means connecting said timer means and said flame proving means-to said first means whereby upon the-ignition of the gas at the burner and the existence of a flame, said valve means is energized for high fire for a predetermined time to shorten the condensation time of the products of combustion.
6. The invention of claim 1 wherein said means comprises a microprocessor having an output connected to the multispeed induced draft blower, a gas control valve means, and a flame ignition apparatus.
7. The invention of claim 2 wherein said first means comprises a microprocessor connected to the temperature responsive control means, said induced draft blower means, said ignition means, and said fuel control means.
8. In a method of controlling the operation of a gas fired furnace having an induced draft blower for inducing the air flow into the combustion chamber and out through an exhaust stack at various rates and a fuel valve for admitting fuel to a burner in the combustion chamber at a low rate and a high rate having the following steps upon the call for operation of the furnace by a space temperature responsive means, energizing the induced draft blower means at a high rate to provide an excessive amount of air into the combustion chamber, energizing the gas valve furnishing gas to the burner at a low fuel flow rate whereby a normal air to fuel ratio exists at the burner and a high air to fuel ratio exists in the combustion chamber downstream of the burner, igniting the fuel at the burner wherein a normal air to fuel ratio exists, sensing the presence of a flame and thus the combustion of the fuel in the combustion chamber, and upon the presence of combustion, operating the blower means at its low rate.
9. The invention of claim 8 with an additional step of operating the gas valve at its high rate for a predetermined time to bring the heat exchanger up to temperature quickly to prevent rusting.
10. The invention of claim 9 with an additional step of reducing both the blower speed and fuel flow rate for normal operation.
11. In a furnace control system having a gas burner with a normal amount of premixed air and fuel comprising an induced draft blower means adapted to be connected to the combustion chamber of a furnace to furnish combustion air, said blower means having at least two speeds, a variable capacity gas control means adapted to control the supply of gas to the burner of the furnace, ignition means adapted to be mounted near the burner in the combustion chamber of the furnace, and first means operative upon a need for operation of the furnace to energize said induced draft blower means, said ignition means, and said gas control means whereby said blower means is operated at a predetermined high speed to provide excessive air to the combustion chamber to maintain a high air to gas ratio in the combustion chamber during ignition of the gas.
12. The invention of claim 11 wherein said first means is a microprocessor control means.
13. An improvement in a control system for a furnace having a multispeed induced draft blower, a variable capacity gas control valve means for furnishing gas to a partially premixed burner with a fixed primary air to fuel ratio, a gas ignition apparatus, and a burner flame sensor means, the improvement comprising, means, upon the starting of an operation of the furnace, for energizing said induced draft blower at a speed to provide a large amount of secondary air to the combustion chamber of the furnace, means for energizing said control valve to supply a low level gas to the burner to have a high air to gas ratio in the combustion chamber and for energizing said ignition apparatus for igniting the gas at the burner, whereby upon the flame igniting at the burner, a "roll out" of the flame is minimized even after long ignition delays, and means responsive to an output of said burner flame sensor means upon the presence of a burner flame for energizing said gas control valve to provide a higher rate of gas flow to the burner thereby providing said combustion chamber with a lower air to gas ratio for normal operation.
14. In a furnace control system comprising combustion air blower means adapted to supply air to a combustion chamber of a furnace and exhaust gas to a stack, said blower means having at least two speeds for two levels of air flow to the combustion chamber, fuel control means adapted to variably control the supply of fuel to a burner in the combustion chamber of the furnace, temperature responsive control means adapted to respond to the temperature of a space to which heated medium is being delivered by the furnace, ignition means adapted to be mounted in the combustion chamber for igniting the fuel at the burner, flame proving means adapted to provide an output upon the presence of ignition of fuel at the burner, first means connecting said temperature responsive control means to energize said blower means-, to provide high level of air flow to the combustion chamber, and to energize said ignition means and said fuel control means to supply a low level of fuel to the burner to be ignited whereby excessive air to the combustion chamber maintains a high. air to fuel ratio in the combustion chamber so that ignition of the fuel is confined at the burner and not in the combustion chamber down-stream of the burner to minimize "roll out", and further means connected to said flame proving means and responsive to said output to energize said fuel control means to supply a high level of fuel to the burner for a lower air to fuel ratio in the combustion chamber.
15. The invention of claim 14 wherein a high air to gas ratio is made with 100 percent excessive air.
16. The invention of claim 14 wherein said fuel control means is a gas control with a high and low fire rate, and comprising, timer means, and means connecting said timer means and said flame proving means to said first means whereby upon the ignition of the gas at the burner and the existence of a flame, said valve means is energized at said high level for a predetermined time to shorten the condensation time of the products of combustion.
17. The invention of claim 13 wherein said means comprises a microprocessor having an output connected to the multispeed induced draft blower, a gas control valve means, and a flame ignition apparatus.
18. The invention of claim 14 wherein said first means comprises a microprocessor connected to the temperature responsive control means, said induced draft blower means, said ignition means, said flame proving and said fuel control means.
19. In a method of controlling the operation of a gas fired heating apparatus having combustion air blower means for providing the air flow into the combustion chamber and out through an exhaust stack at various rates and a fuel valve for admitting fuel to a burner in the combustion chamber at a low rate and a high rate having the following steps upon the call for operation of the furnace by a space temperature responsive means, energizing the blower means at a high rate -to provide an excessive amount of air into the combustion chamber, energizing the fuel valve furnishing fuel to the burner at a low fuel flow rate whereby a fixed primary air to fuel ratio exists at the burner and a high air to fuel ratio exists in the combustion chamber of the burner resulting in inefficient heating apparatus operation, igniting the fuel at the burner wherein the fixed primary air to fuel ratio exists, and since the air to fuel ratio in the combustion chamber is high a "roll out" condition upon ignition of the flame at the burner is minimized, sensing the presence of a flame and thus the combustion of the fuel at the burner, and upon the presence of combustion, operating the fuel valve to Provide a higher rate of fuel to the burner and an air to fuel ratio in the combustion chamber for efficient heating apparatus operation.
20. The invention of claim 19 with an additional step of operating the fuel valve at its higher rate for a predetermined time to bring the heat exchanger up to normal operating temperature quickly to prevent rusting.
21. The invention of claim 20 with an additional step of reducing both the blower flow rate and fuel flow rate to provide an air flow rate and fuel flow rate at a normal air to fuel ratio for efficient heating apparatus operation at a lower fuel input rate for normal operation.
22. In a heating apparatus control system having a gas burner with a normal amount of premixed air and fuel comprising a combustion air blower means adapted to be connected to the combustion chamber of a furnace to furnish air to the combustion chamber, said blower means having at least two speeds, a variable capacity gas control means adapted to control the supply of gas to the burner of the heating apparatus, ignition means adapted to be mounted near the burner in the combustion chamber of the heating apparatus, and first means operative upon a need for operation of the heating apparatus to energize said blower means, said ignition means, and said gas control means whereby said blower means is operated at a predetermined high speed to provide excessive air to the combustion chamber to maintain an excessive air to gas ratio in the combustion chamber during ignition of the gas whereby if ignition does not take place at the burner for a long time period ignition of the gas downstream of the burner in the combustion chamber does not occur.

TABLE I

SELECTABLE OPTIONS

APPENDIX I

CA 388139 1980-10-17 1981-10-16 Integrated control system using a microprocessor Expired CA1183237A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US19783980 true 1980-10-17 1980-10-17
US197,839 1980-10-17

Publications (1)

Publication Number Publication Date
CA1183237A true CA1183237A (en) 1985-02-26

Family

ID=22730953

Family Applications (1)

Application Number Title Priority Date Filing Date
CA 388139 Expired CA1183237A (en) 1980-10-17 1981-10-16 Integrated control system using a microprocessor

Country Status (2)

Country Link
JP (1) JPS5798720A (en)
CA (1) CA1183237A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6507761B1 (en) 1997-12-02 2003-01-14 Rheem Manufacturing Company Boiler system ignition sequence detector and associated methods of protecting boiler systems

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6507761B1 (en) 1997-12-02 2003-01-14 Rheem Manufacturing Company Boiler system ignition sequence detector and associated methods of protecting boiler systems
US6600960B1 (en) 1997-12-02 2003-07-29 Rheem Manufacturing Company Boiler system ignition sequence detector and associated methods of protecting boiler systems

Also Published As

Publication number Publication date Type
CA1183237A1 (en) grant
JPS5798720A (en) 1982-06-19 application

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