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subcool 11-08-2013 09:56 AM

standing pilot keeps going off
 
Hey how do I check to see why a standing pilot keeps going out every other day or so. What should the pressure be going to the pilot? It is nat gas so I would think maybe 1 - 2 since the burners get 3.5? How do you check a thermalcoupler? Is there a flame sensor on a standing pilot?

Thanks for the help

yuri 11-08-2013 10:57 AM

Most of the time it is the thermocouple getting weak from old age and unless you have a special adaptor to test it in the valve I would just replace it as they are cheap $. if the pilot flame is weak or wavering and the pilot burner is dirty that can cause it to get sucked out by the burner or if it is windy outside then a draft can blow it out. post a closeup pic of the flame.

subcool 11-09-2013 03:12 AM

ok so I replaced the thermocouple and it made it worse. Now it cuts out every 45 sec or so. Could it be the gas valve? I do have a constant 27 volts at the valve. I did not get a pic of the pilot, but I did notice when the blower came on the burners started jumping around, so I'm pretty sure they have a cracked heat ex-changer. That would not cause the flame to go totaly out would it? The flame goes out sometimes before the blower comes on as well.

My other question would be what pressure should be at the pilot and can I check it. I didn't think to check it when I was there, but I am going back tomorrow. There other thing I did not check is will the pilot go out with no call. every time is went out today all the burners were on. If it stays on with out burners that would tell me the thermocouple is good, right?

Thanks for the help

beenthere 11-09-2013 07:37 AM

There is not 1 pressure for the pilot, per say. So any pressure reading could be good on 1 unit and bad for another unit.

If you have a cracked heat exchanger. Forget about fixing the pilot issue. Replace the furnace.

subcool 11-09-2013 07:48 AM

They are selling the house so they will let me change it out. They just want it working and will disclose to buyers about the heat exchanger.

The fast I made it worse makes me think I am on the right path. Could it be the valve, if so why did changing the thermocouple make it worse.
Thanks again for the help

beenthere 11-09-2013 08:05 AM

Probably not the valve.

yuri 11-09-2013 08:05 AM

you better condemn and get that furnace replaced ASAP before you get a flame rollout. it is not burning cleanly now and will be producing CO. you will be liable if they get sick irregardless whether you have a license or not.

w/o seeing the pilot flame I cannot tell you what is wrong but probably the thermocouple is not shoved in far enough or making enough contact with the flame to produce enough millivolts to hold in the pilot valve. probably sitting at the dropout point plus a few millivolts and as soon as the flame moves it cools and drops out. the draft from the main flame will move your pilot flame.

this is a VERY bad situation so get the furnace or heat ex replaced. them disclosing it to the new buyer while still using it is not proper or legal once you know about it. if it is at the point where it needs to be shut down and you did not do that or inform the gas co. you can be sued if they get sick. ignorance of the rules is no excuse in a court.

I have been involved with thousands of bad heat exchangers/CO issues etc and the authorities and am trying to save your skin here plus give advice to others reading these posts.

how 11-09-2013 03:16 PM

Step away from the furnace.
Getting that pilot running is just enabling the possible CO poisoning of the home inhabitants.
Have a professional verify if the exchanger is cracked or not.

ben's plumbing 11-09-2013 03:26 PM

could you get us a picture of the pilot assy and valve assy....but don't ignore checking heat exchanger....don't believe you can sell a home with defective furnace..banks won't touch it....ben sr

subcool 11-10-2013 10:04 AM

I have a video, but do not know how to upload it. I am heading there now and will get a picture as well.

How do you upload a video? send it to u-tube first?

yuri 11-10-2013 10:18 AM

Yeah, put it on U tube and put the link here. Check the heat exchanger for cracks if you know how. If not then we can tell you how if we know the make and model. Don't be too proud to ask I tell my apprentices.

Make a video of the pilot w/o the burners on then start the burners and then we want to see the flames when the fan comes on. sometimes you may be seeing orange which is dirt in the burners and not necessarily flame disturbance.


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