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Old 09-16-2010, 08:48 PM   #16
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Gas furnance over-firing, how do I correct?


I would check it once a week for the first 2 months. That valve may still be faulty and wander out of range. 4" is the max I have seen and it may lose its adjustment on its own. I would be uncomfortable with what it is doing.

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Old 09-16-2010, 08:54 PM   #17
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Gas furnance over-firing, how do I correct?


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I would check it once a week for the first 2 months. That valve may still be faulty and wander out of range. 4" is the max I have seen and it may lose its adjustment on its own. I would be uncomfortable with what it is doing.
I don't mess with gas stuff, but meter clocking method is good enough, right?
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Old 09-17-2010, 02:22 AM   #18
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Gas furnance over-firing, how do I correct?


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I don't mess with gas stuff, but meter clocking method is good enough, right?
You should out of respect for our industry and the dignity of the PROs here drop the hvac from you screen name.

Hvac in your name misleads other diy posters in thinking you are a PRO. And yet they read this thread where you did not install your own furnace and didn't have the right tools to check the gas press. You make us look bad.

If you don't mess with gas you are no HVACer.

my 2 cents
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Old 09-17-2010, 03:34 AM   #19
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Gas furnance over-firing, how do I correct?


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I don't mess with gas stuff, but meter clocking method is good enough, right?
If it was good enough. We wouldn't have combustion analyzers. Or check temp rise across heat exchangers.
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Old 09-17-2010, 04:00 AM   #20
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Gas furnance over-firing, how do I correct?


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Originally Posted by hvaclover View Post
You should out of respect for our industry and the dignity of the PROs here drop the hvac from you screen name.

Hvac in your name misleads other diy posters in thinking you are a PRO. And yet they read this thread where you did not install your own furnace and didn't have the right tools to check the gas press. You make us look bad.

If you don't mess with gas you are no HVACer.

my 2 cents
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My registration date precedes yours by an entire year,son. It's what I happened to pick in 2007. I haven't logged in a while. I added a user title to clear any confusion and this is a DIY forum. You are not the one to tell me what my user name should be.

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Old 09-17-2010, 04:19 AM   #21
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Gas furnance over-firing, how do I correct?


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It's what I happened to pick in 2007.

Your screen name, while confusing. Doesn't violate any for um rule I know of.
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Old 09-17-2010, 05:35 AM   #22
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Gas furnance over-firing, how do I correct?


Meter clocking is okay but I would google U-tube manometer. Can make one yourself. Still best to get a Pro to check it but I am concerned you monitor it for awhile for safety. Working with gas is DANGEROUS and not recommended for DIYers but we can't stop people from doing it. I am sure electricians and car mechanics feel the same way about their trade.

In reality the manifold gas pressure will vary/modulate(+- .5"WC) on a high efficiency furnace. Vacuum thru the burner box/heat exchanger varies with outdoor temp and venting setup and sucks on the gas valve to alter the firing rate. Special procedure required and experience to know how to workaround and with that.
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Old 09-17-2010, 11:28 AM   #23
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Gas furnance over-firing, how do I correct?


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Your screen name, while confusing. Doesn't violate any for um rule I know of.
It still does not make it right, but I won't make an issue of it.
You are right about making it confusing, though.
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Old 09-17-2010, 02:54 PM   #24
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Gas furnance over-firing, how do I correct?


Don't forget SON . He was here a year b-4 you

Last edited by kenmac; 09-17-2010 at 03:17 PM.
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Old 09-17-2010, 03:18 PM   #25
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Don't forget SON . He was here b-4 you
Yeah your right he was here before me..

But I can't be his SON! My Daddy wasn't afraid of gas and he knew how to repair.

Another reason he can't be my Daddy is because my Daddy would never have to ask for help on this site to make a repair.
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Old 09-17-2010, 03:50 PM   #26
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Gas furnance over-firing, how do I correct?


Anyways, dead-on calibration is impossible, because heating value changes from time to time due to variation in fuel composition, but here is the outcome. All measurements were taken based on time it takes to go through four cubic feet of nat. gas, then divided by four to improve accuracy.

Furnace rated input: 60,000BTU/hr
Before adjustment: 74,400BTU/hr
After adjustment: 58,400BTU/hr

Am I correct to assume that a few percent under fire is better than 25% over-fire?

There is no other gas appliances here, so it was the only thing burning gas. I don't see why energy content of fuel * rate of flow isn't enough to calculate BTU input.

Yuri: what's odd...
(I called service for this, didn't do it myself)
The valve pressure adjustment was not responding at all, for a while. It had to be unscrewed a lot before it became responsive at all, but at that point, it was responding perfectly. I'll check again when heating season comes in, but I'm not messing with gas line. I'm going to clock it, and if its skewed significantly, then I'm going to make a service call. I don't mess with gas pipes, period.
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Old 09-17-2010, 04:11 PM   #27
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Gas furnance over-firing, how do I correct?


What will give you an almost perfect burn is a combustion analyzer.
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Old 09-17-2010, 06:19 PM   #28
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Gas furnance over-firing, how do I correct?


Turning the screw in increases the pressure but it sounds like it was bottomed/maxed out by a pizzed off worker. Meter clock it and you should be OK.

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