Original message
| DmitryNK
 |  "Gas Furnace cycling"
, posted Sat 20 Dec 19:07  
My York (Central Environmental Systems) has been cycling. The furnace starts as normal, but 30-60 econds later, it shuts off (looks like the gas supply is shut off). The blower keeps running. Hot Surfice Igniter lights almost immediately after the shut down, and the furnace restarts within about 10 seconds. Then, the cycle repeats iteslf.
1. I cleaned the the rod which detects flame, as advised by gas company representative. It did not eliminate the problem.
2. I shorted white and red thermostat wires. The probelm persists, so the thermostat should be OK.
3. Because of cycling, the air was not warming up, and I had to reduce the temperature setting on the blower down to 90 degrees. The house temperature does not heat up above 70 degrees even with thermostat setting at 80 all day.
Please advise,
Dmitry
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Replies:
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| xenos
Webmaster 
| "Re(1):Gas Furnace cycling" , posted Sat 20 Dec 19:15
It’s either the flame sensor. A limit or the air proving switch. Turn on the main fan to eliminate the limit, since you have cleaned the flame sensor I would concentrate on the air proving switch maybe it’s opening when the burner fires.
Xenos.
The best way to escape a problem is to solve it.
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| | DmitryNK
| "Re(2):Gas Furnace cycling" , posted Mon 22 Dec 22:20
Thank you for advise.
I've been changing the limit control settings. I have turned the rotating dial a number of times trying to start the main blower before I read the warning "CAUTION! DO NOT ROTATE-HOLD DIAL WHEN ADJUSTING POSITIONERS" . Did I mess up ! Could be the reason for cycling !
Whre is the air proving switch located !
Thank you,
Dmitry
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| | xenos
Webmaster
| "Re(3):Gas Furnace cycling" , posted Tue 23 Dec 08:39
No don’t worry about it, we do it all the time LOL. Now over doing it may damage it. Standard settings would be 90,150,200. If the 90 and 150 are too close it will cycle.
Xenos.
The best way to escape a problem is to solve it.
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| | DmitryNK
| "Re(4):Gas Furnace cycling" , posted Tue 23 Dec 21:04
The furnace is cycling with main blower either on or off. You mentioned air proving switch in previous e-mail, where can I find it and how to test it !
Thank you for your help,
Dmitry
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| | xenos
Webmaster
| "Re(5):Gas Furnace cycling" , posted Tue 23 Dec 21:16
It will be connected to the Venter motor. Testing it would require a volt meter and monitor it. But this sure sound likes a flame current issue. The sensor you cleaned was it a single rod/wire?
Xenos.
The best way to escape a problem is to solve it.
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| | DmitryNK
| "Re(6):Gas Furnace cycling" , posted Wed 24 Dec 18:17
The flame current sensor is a rod 3-inch long about 1\8-inch diameter. The flame shutdown is very abrupt, the flame however looks good when it is on.
Dmitry
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| | xenos
Webmaster
| "Re(7):Gas Furnace cycling" , posted Wed 24 Dec 18:44
That’s the sensor alright. I would ground one of the burners since it sure sounds like flame current or the pressure switch on the Venter motor.
Xenos.
The best way to escape a problem is to solve it.
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| | ohnurse
| "Re(8):Gas Furnace cycling" , posted Tue 18 Dec 02:38
Looks like last year you all had this problem. I have it this year. My scenario is very similar, but let me be more specific.
Cycling from off to on repeatedly occurs in about 3 minutes. From dead start, pilot light element goes on fine, blower for external air starts fine, gas valve opening starts fine, flame starts fine. Pilot element light turns off fine. 15 seconds later, blower goes on fine. 15 seconds later, flame cuts out. Blower for external air cuts out. 15 seconds later, blower for main ventilation cuts out. everything is dead.
The difference I note from earlier posts is that the flame lives happily for 15-20 seconds. If I disconnect the flame sensor, it lasts for 1-2 seconds.
Flame sensor is therefore not totally dead. Maybe just ineffective in maintaining output needed to send signal that flame is on. Alternatively, the receiving unit might not be picking up the whole signal?
I am going to try to by a new flame sensing unit.
Any other comments are appreciated. Any advice on where to buy one of these things is appreciated. Anyone want to tell me why the flame sensing unit appears to have only one output is appreciated. Isn't this s thermocouple that creates a voltage difference and therefor needs two wires for a difference?
Regards, C
C
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