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Gas furnace goes off excessive gas flow?


Vlado's Avatar
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02-08-18, 01:00 AM   #1 (permalink)  
Gas furnace goes off excessive gas flow?

Hi Folks, I am facing quite new and unusual (for the HVAC pros in my area) issue: my gas furnace won't stay lit unless I adjust the gas flow control arm on the main pipe that goes in the furnace. Once lowered, it is working quite steadily and does not go off.

Any suggestions on WHY is this happening and how to fix it (need it running @ its fullest, huh:?), would be highly appreciated!

 
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02-08-18, 04:47 AM   #2 (permalink)  
A better explanation is needed. What is the gas flow control arm and what does it look like and do?. What is the age of the furnace and make and model number. Pictures would be helpful

 
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02-08-18, 07:20 AM   #3 (permalink)  
What is shutting the furnace off?
The manual gas shutoff valve is NOT a throttle.

 
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02-08-18, 04:27 PM   #4 (permalink)  
Hi, thanks a million for your prompt response(s). The gauge, the arm is on the pic. The furnace is 15 yo, Carrier. Cheers, V

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Last edited by Vlado; 02-08-18 at 06:27 PM.
 
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02-08-18, 06:29 PM   #5 (permalink)  
When the manual gas shutoff is semi-opened, the furnace works okay. Once fully opened, excessive gas overflows the burner?

 
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02-08-18, 06:36 PM   #6 (permalink)  
Welcome to the forums.

That IS a problem and would suggest a defective gas valve.... in particularly the regulator stages. If you have a technician.... have him check the manifold gas pressure. If you don't have a tech..... check with your gas supplier. They employ some good field technicians and will take care of the problem without gouging or trying to sell you a new furnace.... unless it's absolutely necessary.

That MUST be addressed as soon as possible.


~ Pete ~

 
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02-09-18, 04:56 AM   #7 (permalink)  
Running the furnace like that is potentially dangerous, and can cause damage to the furnace. It must be fixed ASAP.
Closing that valve down like that is not a fix.

 
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02-09-18, 01:16 PM   #8 (permalink)  
Guys, many thanks for your kind responses and direction, much appreciated. Where can you see the danger in semi-shut gauge?

 
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02-09-18, 04:21 PM   #9 (permalink)  
Improper gas flow/pressure/volume.
Improper use of that valve. It isn’t designed to be a throttle or operate in a mid position like that.

 
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02-10-18, 06:05 PM   #10 (permalink)  
So I guess the question is still there... Anyone with any ideas of what is causing this? Thanks!

 
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02-10-18, 07:59 PM   #11 (permalink)  
You need to start by
Taking gas pressure readings on the input and manifold side of the valve.
Measure temperature rise across the heat exchanger.

 
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02-10-18, 08:06 PM   #12 (permalink)  
Sure. It is a malfunctioning pressure regulator incorporated in the combination gas valve. It MAY be simply in need of adjustment if it has always been this way or it may need to have the combination gas valve replaced and the pressure regulator properly adjusted. Generally speaking this is NOT a DIY job.

 
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02-13-18, 05:26 AM   #13 (permalink)  
Any updates here? Get it fixed up?

 
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02-13-18, 10:52 AM   #14 (permalink)  
Guys, many thanks for your contribution and all of the advices! I am in the process of fixing it and will keep you appraised once finished. Cheers, Vlad

 
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02-16-18, 04:05 PM   #15 (permalink)  
Guys, a quick update on the issue. The Christin HVAC, Inc. rep came to fix it, measured the gas pressure, adjusted it just a little bit and said it should be alright now. Not! The problem is still there, and once he realized that it's something else, he said it is thermocouple, which need to be replaced. Asked for $311 on top of $187 that I already paid... Asked him how likely is that the thermocouple is causing this, given that it has been replaced a month ago and the problem is still there... So $187 wasted, thinking of suing these idiots for guesstimating and making 3 holes in furnace... Cheers!

 
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02-16-18, 06:06 PM   #16 (permalink)  
That does not seem to have the symptoms of a thermocouple problem.
What was the gas pressure and what did he adjust it to?

 
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02-17-18, 10:24 AM   #17 (permalink)  
V,
The job of the thermocouple is to tell the gas valve it's OK to open. It has nothing to do with regulating gas pressure.

As PJ suggested that is the job of the gas valve which has a regulator built in.

If the thermocouple was your problem by not sensing the heat to open the gas valve you would have no fire at all.

Unless I'm missing something I can't understand why they keep looking at the thermocouple and not taking gas pressures and look at the gas valve.

Just my thoughts, hope this helps a little.

 
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Yesterday, 08:40 PM   #18 (permalink)  
Guys, thanks a lot for all of your responses. Please see the pic. The MF drilled three holes in the system for no reason! Is that too bad for the furnace? New concern now

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