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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7532
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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We have a Pennco gas furnace Model # 15b070fv Serial #

Customer Question

My name is Alu.
We have a Pennco gas furnace Model # ***** Serial ####-##-#### ***** btu. The pilot keeps going off when the furnace fires up. The service people have replaced the gas valve, controller, rollout switch, etc., but the problem persists. They left the covers (the inner and the outer) open and found that it took care of the problem. When the covers are on the problem continues. They "think" it might be a backdraft due to chimney issues.
The chimney people want to put a new lining (costs a lot!), but wouldn't guarantee that it would solve the problem. There must be a way to test for the cause of the problem.
Thanks for any help.
Submitted: 7 months ago.
Category: HVAC
Expert:  Eddie replied 7 months ago.

hi Alu .............when was the last time they vacuumed out the chimney base?.........if it is old there could be a lot of debris collected down there..........can you smell almost a sweet hydronic smell? like a you know where your damper switch is? time it goes off....... try that and see if it comes back on........if your chimney is over 30 years old it would be a good idea to put a liner in

Customer: replied 7 months ago.
The base was vacuumed. No smell. The furnace is 6 years old. What and where is the damper switch?
Expert:  Eddie replied 7 months ago.

it should be a little button where the exhaust coming up from the burner to a round hood part and then to the flue..........but it should be on that hood part ..........look for anything with 2 small low voltage wires going to it .............being it is only 6 years old it might be an automatic old is the chimney ?

Customer: replied 7 months ago.
You're right, the service guy told me it is automatic. You should be able to tell from the model # ***** I gave you.They have exhausted everything in the furnace itself. Can you suggest a way to test for backdraft, IF that's what is causing the problem? Is there a way to "heat" the chimney and see if the problem stops? Or maybe put a fan to push the air out?
Customer: replied 7 months ago.
There is another gas Pennco furnace (2 yr old) and two gas water heaters going up the same chimney. No problems with any of them.
Customer: replied 7 months ago.
Please let me know if you are getting back to me.
Expert:  Eddie replied 7 months ago.

well that was the only thing I was going to suggest if it was in fact the flue and damper control............a seasoned veteran can put his hand by the hood and see if he is getting back pressure .....especially on a day when the air is heavy

Expert:  Eddie replied 7 months ago.

I can opt out and see if one of my colleagues would be able to add anything else to this issue ..................good luck in resolving

Customer: replied 7 months ago.
Well, as I said, several experts have eliminated all problems with the furnace itself. So far, I haven't heard anything new from you. If it doesn't cost me any more, I would like to chat with another technician and see what they come up with.Thanks!
Expert:  Eddie replied 7 months ago.

of course .............don't click any rate buttons and you won't be charged for our time here..........once I opt out someone might offer a different perspective like I said to resolve your problem ............again good luck


Customer: replied 7 months ago.
Thanks eddie.
Expert:  Eddie replied 7 months ago.

you're welcome

Expert:  Phil replied 7 months ago.

Hello, tell me how the exhaust vent pipe is laid out from the furnace to the chimney, and all about the chimney, what size is it inside approximately, how tall is it, and what is it made of.

Tell me if this pilot going off situation developed over time or has it always tended to do that.

What size is gas line, and about how long is it.

Please describe the pilot flame, is robust and 'fierce' or a lot softer.

Describe what you see, while looking at the pilot as the main burner comes comes on, is the pilot flame being drawn off of the pilot?

So far I suspect the pilot orifice might be slightly restricted...

Customer: replied 7 months ago.
We never had a problem in the 35 years we have owned the property. Chimney is 35 ft. Flues 8 x 8. Pilot flame robust.I cannot tell the size of the gas line. The gas line and everything else is the SAME for both Pennco furnaces. The flame is drawn off the pilot when the furnace goes on. All parts involving the gas valve, pilot, rollout switch, controller, etc., are new and original.Please remember that everything is fine when the doors (the inner and outer) are kept open. The problem starts only when we close them.
Expert:  Phil replied 7 months ago.

Thanks for the excellent feed back.

This should be the manual, let me know if this is what you have or not, and if yours has the display panel shown on page 24 and if it does, are there any error code read outs.

Regarding the issue of the flame not going out when the door is open, that would be because when the door is open, combustion air goes from the open front to the burners, and does not sweep up past the pilot through a bottom opening as it does when the door is closed. Look for that, and tell me how much space there is between the bottom of the boiler and the floor.

We can go from there.

Customer: replied 7 months ago.
We don't have the display panel. I am not right now at the address where the furnace is located, so I cannot tell how much space there is between the bottom and the floor. I can let you know later. Is it okay to get back to you next week?On another matter. I wonder if leaving the inner door to the burner open is safe. Is it safe to leave both doors open? I have had it open for a couple of weeks now.
Expert:  Phil replied 7 months ago.

Hello again, If you rate my input so far positively, you can get back to me next week even if the question 'times out' or says 'closed'..just post your remark anyway, I will get it, and we can go from there.

There is considerable risk running with the inner door removed, meantime look under the boiler for any debris that may be blocking the air flow, and causing the velocity past the pilot to increase.

Customer: replied 7 months ago.
Thanks Phil. I'll get back to you on Monday.
Expert:  Phil replied 7 months ago.

That works