payne gas heater (Burner Cycling Problem)

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  #1  
Old 11-13-04, 01:47 PM
beefovail
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payne gas heater (Burner Cycling Problem)

I just bought this house one month ago so history is not known. I have a payne gas heater converted to propane. My troubles started the other nite when I tried to fire the ol boy up. Pilot would lite,burners would lite and run for a minute and promptly shut down. Every once in a while the blower would fire up just before burners shut down. I researched the problem on this site and was certain it was the flame sensor. $75.00 later I installed it and fired it up......same hooey. I pulled the limit switches out and tested them,they seem good,no resistance,put flame to them they popped. Ok, put them back in the unit and fired it up and YEE HA,HEAT. It ran for about 4-5 minutes and shut down. This is great!! I thought that the t-stat thermometer was of a bit so I adjusted it and fired the old boy up again. NO PILOT!!! The ignitor was doing it's thing but no gas. Back to the wiring diagram and I'm looking at this thingamabob called a lockout timer which seems to control gas flow. Im thinking this may be malfunctioning. Any help would be appreciated. I did replace the filter and clean all the burners. The flames were a nice blue when it did work,fan on or not. model # is 394gaw048100,series 2388a00675
thanks so much.
 

Last edited by beefovail; 11-13-04 at 01:49 PM. Reason: forgot model #
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  #2  
Old 11-13-04, 06:20 PM
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Arrow Cycling On High Limit A Possibility or Safety Related Condition

Hello beefovail. Welcome to the Heating Furnaces forum topic and the Do It Yourself Web Site.

Based soley upon the info you provided, air ciculation is a likely cause. Chances are the air filter is restricted, too many warm air registers are closed restricting air flow, the fan motor could be turning too slowly, the intake air register is blocked by furniture, the solenoid on the gas valve is defective, firebox is smothering, there could be a restriction in the venting system, the A/C coils could be restricted with dust and lint, etc.

Be sure the fans blower cage will revolve freely. The blower cage has bearings on each end. If the cage only does not rotate freely, the end bearings could be the cause of the problem. Same may apply to the motor bearings. Slow fan speed will cause firebox to over heat cycling the buners off to prevent over heating.

The burners are cycling on and off because the interior firebox is reaching it's highest allowable temperature. If the high limit switch did not cycle off the burners, firebox melt down would occur. Continuous cycling of the burners without cooling off the firebox can create firebox damage.

I would suggest looking for an air flow problem. Any restriction to the air intake and or to the warm air registers or through any part of the air circulation system is likely the primary cause for the cycling to result.

Check the filter. Replace or clean as needed. Open all warm air registers fully.

May be a piece of furniture is too close to the intake air supply and restricting the intake. Could be a defective blower motor that spins too slowly or any of many other air flow problems.

The above conditions will still allow the fan to run but the restricted air flow causes the furnace to overheat which then activates the high limit safety switch which in turns cycles the burners off until the firebox cools down some.

Other possible and or probable causes:
Assuming the firebox {Heat Exchanger} isn't cracked and or the burner flames aren't smothering, etc.

Defective Gas Valve Solenoid:
The gas valves solenoid is internal. Take the entire gas valve unit to your local appliance parts store and have the entire assembly and parts tested.

Defective Gas Valve:
Remove entire unit as an assembly. Take the entire assembly to your local appliance parts store for testing. Gas valves are not repairable. Replacement is the only option if defective.

CAUTION: Do Not attempt to repair the gas valve! This is a non repairable item!

Restricted Flue. Restricted Venting System.
Many variations and many possible causes on this issue.

Some of the above pertaining to the firebox and or flu restrictions, etc can be an unsafe operation conditions of the heater. Heater shutting off on a safety device, as intended and designed to do, etc. In some cases, only a professional heating agent can diagnose the condition and determine the cause.
 
  #3  
Old 11-13-04, 07:41 PM
beefovail
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thanks for the reply

I don't think I have an overheating problem as I put my ohm meter to both the limit switches when I had the no start problem and both were open. I was just out for a while and turned it on when I got home,it cycled perfect.
I replaced the filter yesterday and cleaned the burners also. There is no blockage at the intake either,so this is why I'm questioning whether this Lockout timer may be defective. Do you have an idea what the purpose of this timer is? It is shown on the supplement wiring diagram for the lp conversion.
I just now tried it again and the ignitor just tries to lite the pilot but apparently the gas is shut off because it's not lighting. It has been about 10 minutes since it ran last so I would assume the box is cooled down.
Thanks for your assistance.
 
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Old 11-13-04, 08:04 PM
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Hello: beefovail

No. High limit switch is not suppose to be opened. Closed. Allows current to flow closed. 10 minutes is not sufficient time to cool an overheated firebox. If overheating had occured, the high limit switch would be opened to break current flow to the gas valve, shutting off buners to prevent overheating.

To cool firebox faster, turn T-Stat switch to fan ON setting for 10-15 minutes. Allow plenty of time for cooling. Turn T-Stat to fan off or back to auto. No heat setting just yet. Do not turn T-Stat to heat just yet after cooling off firebox.

Go back and re ohm fan high limit switch. Switch should ohm to closed, full needle swing indicating continuity. Power to unit off at main electrical power or plug out plug from wall outlet when doing ohm testing. Ohm testing not power testing.

Note the test results and post them back. Plus answer to question below.

You said: "Ignitor doing it's thing" Exactly what does that mean???

A spark ignitor (ISID) sparking (ISID means Intermitten Spark Ignition Device) to light a pilot flame????

Or a glowing hot surface (HSI-IID) ignitor glowing????

Which one??? HSI or ISID???

Trying to help you. Need answers.

In my opinion, based upon info provided & as problem is described...furnace is over heating. Shuting down on hight limit, there is a smothering flame condition or a venting problem.

Have to start at the begining with the diagnostic procedure. A step by step process to determine the cause. Need question above answered in details first.
 
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