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Old 12-26-2008, 05:21 PM   #16
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by key1cc View Post
I am not suprised.
...being that this is the DIY site.
How might one go about correcting this BTU deficet?

Key1
Need a manometer, to connect to the manifold side of the gas valve.

Once you have one and connect it(need 1/4"MIP to what ever size hose barb fitting).
Run the furnace in low fire, and adjust the gas pressure to I believe its 1.6" for Trane in first stage(check installers manual).

Also, you need to pull off teh hose that runs from the gas valve to the burner box, and remove teh burner cover plate.

Be carefull not to damage plate seal.

Also, you must then check the gas pessure in high fire. And then recheck low fire. Adjustment of one does effect the other.

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Last edited by beenthere; 12-26-2008 at 05:49 PM.
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Old 12-26-2008, 05:25 PM   #17
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How to confirm 2nd stage burner working?


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Originally Posted by beenthere View Post
What your calling actual, is the output.

But to get that output, you must have the higher input.

EG: Input of 65,000 BTUs times 95% efficiency = 61,750 BTUs output.
DUH

Makes more sense now. Thanks for the clear up.
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Old 12-26-2008, 05:27 PM   #18
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How to confirm 2nd stage burner working?


Was reading the Lennox info and apparently you are supposed to multiply the reading by the htg value of the fuel to be more accurate. Around here it is supposed to be 1050-1100 / cu.ft so that would bump up our posters results. As a rule of thumb I usually use the chart X 1000 to get close enough. I also use a manometer to check the actual gas pressures. The gas valve will modulate slightly with the draft thru the heat exchanger/hose from the burner box does that job to compensate for the venting.
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Old 12-26-2008, 05:34 PM   #19
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How to confirm 2nd stage burner working?


It still sounds like hes going to be good for stage one of heating, but I'm waiting to see what he comes back with for stage 2. Should be easy enough to tell if it goes up quiet a bit.
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Old 12-26-2008, 05:42 PM   #20
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How to confirm 2nd stage burner working?


I just switched her to 2nd stage and timed the meter. (again water heater, stove, and dryer all confirmed off). I repeated the measurement 4 times and twice I got 21 seconds and twice I got 19 seconds.

If 21 seconds is correct I'm low at 86000 BTU.

If 19 seconds is correct I'm right on at 95,000 BTU.

Tomorow in the day light I will recheck all using the 2 cubic foot dial instead of the 1/2 cubic foot dial....... since it moves at 1/4 the speed (much slower) it may result in a more exact measurment since 1 second makes a big difference.

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Last edited by key1cc; 12-26-2008 at 05:44 PM.
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Old 12-26-2008, 05:57 PM   #21
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How to confirm 2nd stage burner working?


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Originally Posted by yuri View Post
Was reading the Lennox info and apparently you are supposed to multiply the reading by the htg value of the fuel to be more accurate. Around here it is supposed to be 1050-1100 / cu.ft so that would bump up our posters results.
My Trane info states the same thing. How do you obtain the "heating value" for Princeton, NJ?

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Old 12-26-2008, 06:03 PM   #22
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How to confirm 2nd stage burner working?


Call the gas company, and ask them the BTU content.
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Old 12-26-2008, 07:14 PM   #23
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How to confirm 2nd stage burner working?


Well I decided to grab a flashlight and go out side and re-run the numbers using the 2 cubic foot dial for better accuracy. When I used the 0.5 cubic foot dial each measurement took 20-30 seconds so being 1 second off makes a big difference.
Using the 2 cubic foot dial each measurement took between 81 and 120 seconds so much more accurate.

Here are the results:

Stage 1, 120 seconds = 60,000 btu input
Stage 2, 81 seconds = 89,000 BTU input.

Looks like Beenthere is correct and I am short 5k BTU on stage 1 and 6k BTU on stage 2.

According to my PSE&G Bill I beleive my Heating value is 1012 so that only bumps me to 61,000 BTU and 90,000 BTU.

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Old 12-26-2008, 07:20 PM   #24
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How to confirm 2nd stage burner working?


Is there a downside to being low on BTU's if my home is being sufficiently heated? I understand that it takes a given amount of BTU's to heat an area, whether it happens fast or slow.

Wouldn't this mean my furnace would just run a little longer to get the home to the set temperature? Ultimately resulting in the same BTU cost as if the furnace BTU's had been set higher?

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Old 12-26-2008, 07:27 PM   #25
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How to confirm 2nd stage burner working?


You are correct. Altitude and some other factors/venting/gas valve modulating will affect your readings. I would not worry about anything. It is worthwhile to get a tech to check the manifold pressures at some time.
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Old 12-27-2008, 05:47 AM   #26
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How to confirm 2nd stage burner working?


It depends what your temp rise is.

If your temp rise is low. Then it could cause condensation in the primary heat exchanger. And the primary is not designed to have condensation happen in it.

2 stage units are a couple % less efficient in first stage to begin with.
So your just a bit less efficient yet with an under fired first stage.
So instead of being at 92 or 93%, you may be down to 89 or 90% in first stage.

Check your temp rise.
Then do the math.
(temp rise times 1.08) times CFM equals BTU output.
See what it says.
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Old 12-27-2008, 11:14 AM   #27
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by beenthere View Post
It depends what your temp rise is.

If your temp rise is low. Then it could cause condensation in the primary heat exchanger. And the primary is not designed to have condensation happen in it.

2 stage units are a couple % less efficient in first stage to begin with.
So your just a bit less efficient yet with an under fired first stage.
So instead of being at 92 or 93%, you may be down to 89 or 90% in first stage.

Check your temp rise.
Then do the math.
(temp rise times 1.08) times CFM equals BTU output.
See what it says.
Temp Rise = 48Fx1.08x1180CFM=61000BTU

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Old 12-27-2008, 11:23 AM   #28
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How to confirm 2nd stage burner working?


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Originally Posted by beenthere View Post
.....So instead of being at 92 or 93%, you may be down to 89 or 90% in first stage.
Please clarify.

I thought that my 95% AFUE furnace utilizes 95% of whatever amount of gas that goes through it. If 65000 BTU's went through it, would it not utilize 95% of the 65000 and have 61750 output??
However if 60,000 btu's went through it, the furnace would only utilize ~90% of the 60,000 (or 54000 BTUs) ??? Why would it not utilize 95% of the 60,000??

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Old 12-27-2008, 11:47 AM   #29
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How to confirm 2nd stage burner working?


Less gas, means less radiant heat transfered to the heat exchanger.

Cooler heat exchanger means it puts off less radiant heat to the jacket/insulation foil face. So less BTU transfer.




PS: Don't check temp rise directly above the heat exchanger.
The thermal probe can pick up radiant heat, and give you a false higher temp reading.
Should be taken in the trunk line, out of sight of the heat exchanger.
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Old 12-27-2008, 05:41 PM   #30
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How to confirm 2nd stage burner working?


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Originally Posted by beenthere View Post
PS: Don't check temp rise directly above the heat exchanger.
The thermal probe can pick up radiant heat, and give you a false higher temp reading.
Should be taken in the trunk line, out of sight of the heat exchanger.
I check temp rise in the plenum above the coil. Is that too close to the heat exchanager?

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