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Old 12-26-2008, 08:19 AM   #1
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How to confirm 2nd stage burner working?


Hello all,

I have a 3 yr old American Standard Freedom-90 Dual Stage Comfort-R Furnace model AUY060R9V3W. I don't know if its my imagination or not but it seems that for the past week when it enters second stage that the warm air exiting the ducts isn't as warm as it used to be. The blower kicks into higher speed but the air temp doesn't seem to get any warmer as I believe it should at a higher btu rate. Further information, this furnace has sealed combustion. I can't get a good view of the burners to see if they're changing when it goes into 2nd stage. I see no flashing trouble codes other than the fast flashing green led(call for heat) and the red led flashes once about every 20 seconds. During operation, when in 2nd stage, I tapped gently on the gas valve(maybe was not reaching 2nd stage) but nothing changed. Now for my questions if I may:

1) How can I confirm that the burner is kicking into 2nd stage btu?
2) If this type of furnace kicks into 2nd stage but the burners remain in
1st stage btu, would this cause some kind of abnormal flash code of
the green and/or red LED?

An off topic related question:

1) If I call a HVAC company for a furnace tune-up/cleaning should they disassembe the sealed combustion box and clean the burners etc? It appears to have some red RTV or other type sealant on the seams. I just want to be sure that the tech will open, clean burners and reseal the box.
2) Is red RTV used to seal the seams of a sealed combustion box?

Thanks for reading my message. Any thoughts appreciated.

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Old 12-26-2008, 08:38 AM   #2
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How to confirm 2nd stage burner working?


They should open that box and inspect the burners and clean the flame sensor and see if any debris/leaves/bugs got sucked into there. It is under negative pressure and I have seen none of them sealed with RTV silicone. The air temp may be the same on high fire as low fire as the fan will speed up when it goes to high fire. I would have the tech meter clock the furnace to make sure it goes to high fire and/or check it electrically. In the owners/installers manual there may be a meter clock chart which you can follow. Basically you look at the chart/find a 1 cu.ft dial on the gas meter and count the seconds for the dial to make one revolution and compare them to the chart to determine the firing rate. The firing rate is on the model # sticker.

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Old 12-26-2008, 08:45 AM   #3
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How to confirm 2nd stage burner working?


They should open it and do as Yuri said.

You can look at your gas meter when you know its in low fire.
Then turn your stat up and waut for the blower to increase speed, then look for yourself if the gas meter has increased in speed.

Its possible that the gas valves regulator isn't letting as much gas through as it should.

So they should also check the manifold pressure of both stages of heat.
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Old 12-26-2008, 08:50 AM   #4
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How to confirm 2nd stage burner working?


Good points. Have them check the small 1/4' hoses from the gas valve to the burner box etc. Those hoses will regulate the gas valve pressure. Make sure they use a manometer to check both gas pressures low/high fire. Ask the company to send an experienced tech who has/knows how to use a manometer. Lots of newbies/hackers don't.
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Old 12-26-2008, 08:55 AM   #5
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How to confirm 2nd stage burner working?


Thank you yuri and beenthere for your replies. I appreciate it. I will do the gas meter thing first and if it increases gas usage I'll assume its working ok.

Thanks again!
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Old 12-26-2008, 09:52 AM   #6
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by yuri View Post
. I would have the tech meter clock the furnace to make sure it goes to high fire and/or check it electrically. In the owners/installers manual there may be a meter clock chart which you can follow. Basically you look at the chart/find a 1 cu.ft dial on the gas meter and count the seconds for the dial to make one revolution and compare them to the chart to determine the firing rate. The firing rate is on the model # sticker.
Good insight.
I think I'll check this also just for confirmation. One question. My instructions has a chart that provides gas flow in cubic feet per hour (CFH) which I can figure out by timing the revolutions on my gas meter.

However, I am supposed to multiply this CFH number by the "heating value" of the gas obtained from the utility company. Is that "heating value" the Therms? My PSE&G bill provides me Therms and CCF (whatever that is).

Thanks for your help.

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Old 12-26-2008, 11:31 AM   #7
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How to confirm 2nd stage burner working?


Here is the chart I use. The firing rate ie: 36 =36,000 BTU's/hr. THe gas htg value varies slighty but is not a major concern.
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Old 12-26-2008, 03:02 PM   #8
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by yuri View Post
Here is the chart I use. The firing rate ie: 36 =36,000 BTU's/hr. THe gas htg value varies slighty but is not a major concern.
Thanks, my data below is very similar but on a 2 cubic foot dial.

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Old 12-26-2008, 03:11 PM   #9
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How to confirm 2nd stage burner working?


It helps to use a stopwatch/repeat the process 3 X and average the results. Make sure the water heater or no other appliances are running at the same time.

Good Luck
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Old 12-26-2008, 04:29 PM   #10
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by yuri View Post
It helps to use a stopwatch/repeat the process 3 X and average the results. Make sure the water heater or no other appliances are running at the same time.

Good Luck
All done

My gas meter had the 1/2 cubit foot dial so I divided my flow number by 4 as instructed. I measured 4 times. twice I got 29 seconds and twice I got 31 seconds. If I believe the 29 I get a value of 62 (which I presume implys 62,000 BTU.). If I believe the 31, I get a value of 58 which implys 58,000 BTU. Soooo my furnace in stage 1 is using somewhere between 58,000 and 62,000 BTU. I have a Trane XV95 2 stage unit rated at 100k btu input 2nd stage and 65k btu input in 1st stage.

looks like I'm low.....not sure what it means though.

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Old 12-26-2008, 05:02 PM   #11
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How to confirm 2nd stage burner working?


60,000 sounds about right for the 1st stage. If you have a true 2 stage tstat with a wire connected to a W2 on the tstat and the circuit board then it should shift into 2nd stage if you increase the temp by more than 1-2 degF. If using a single stage tstat then the board will have a timer of 7-15 minutes (I am not sure about Trane's timing) before it goes into 2nd stage. It should take awhile B4 it goes thru its timer and then you need to meter clock it again. Depends on how the installer setup the dip switches on the circuit board. Try it again after 10 mins of running on low fire. Some of our other guys may be more familiar with that unit and know the timing biz. I am mostly a Lennox/Carrier guy. That info may be in the installation manual.
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Old 12-26-2008, 05:04 PM   #12
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How to confirm 2nd stage burner working?


Your 3000 to 7000 BTUs light in low fire.

Another thing your original installer didn't set up.
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Old 12-26-2008, 05:07 PM   #13
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by beenthere View Post
Your 3000 to 7000 BTUs light in low fire.

Another thing your original installer didn't set up.

I am not suprised.
...being that this is the DIY site.
How might one go about correcting this BTU deficet?

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Old 12-26-2008, 05:08 PM   #14
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How to confirm 2nd stage burner working?


I also have an XV95 (smaller unit tho 52k,80k btu's). I'm not sure if yours is an upflow like mine also, but asuming yours is (I think downflow btu #'s are the same anyways) you should have part number TUH2C100A9V4VA

Look at page 6 of this trane manual for upflow and page 7 for down flow #'s
http://www.trane.com/webcache/un/furnaces%20(furn)/product/22-1814-02_01012008.pdf

The rated input is 65,000 btu but the actual is 61,750btu. This puts you right where you should be for your first stage.

Same goes for the 2nd stage. Its rated for 100,000btu but actual is 95,000btu.

The #3 next to the numbers says "Based on U.S. government standard tests."

Also altitude will play into this to some degree. So I think your fine on your findings for stage one. Now lest test stage 2. Crank that t-stat to 90 degrees inside and see what she can do.


Edit: I did check and the down flow BTU's are the same readings so either way 61,750btu acutal is the correct number for which ever model VX95 you have.

Last edited by integlikewhoa; 12-26-2008 at 05:11 PM.
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Old 12-26-2008, 05:15 PM   #15
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How to confirm 2nd stage burner working?


Quote:
Originally Posted by integlikewhoa View Post
Look at page 6 of this trane manual for upflow and page 7 for down flow #'s
http://www.trane.com/webcache/un/furnaces%20(furn)/product/22-1814-02_01012008.pdf

The rated input is 65,000 btu but the actual is 61,750btu. This puts you right where you should be for your first stage.

Same goes for the 2nd stage. Its rated for 100,000btu but actual is 95,000btu.

The #3 next to the numbers says "Based on U.S. government standard tests."
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.

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