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Old 12-27-2008, 04:50 PM   #31
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How to confirm 2nd stage burner working?


That should be ok.
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Old 12-27-2008, 07:38 PM   #32
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How to confirm 2nd stage burner working?


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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.
My installation instructions state that my temp rise range is 35-65F.
So it looks like I am ok at 48F.

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Old 12-27-2008, 08:00 PM   #33
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How to confirm 2nd stage burner working?


After rechecking......

my 48F Temp rise occurred with my humidifier bypass open. I believe it should be done with the bypass closed, correct? If that is the case, then the temp rise with the bypass closed if 45.3F

45.3x1.08x1180CFM= 57,730 BTU's output .....confirming what Beenthere indicated, that I am low on BTU's.

I will now look into what is required (special tools) to increase the gas pressure to bring the BTU's up to the stated value.

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Old 12-27-2008, 10:05 PM   #34
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How to confirm 2nd stage burner working?


Well, I read the installation manual on checking/changing the gas manifold pressure. Considering I am accustomed to dealing with gas (installed gas fire place, gas ovens, gas dryers,etc) I am not to intimidated.

It looks very straight forward. My current magnehelic guage only goes up to 1.0 W.C. so I need to wait until I get one that goes to at least 4 W.C. since my unit calls for a 1.7" W.C. Max. for 1st stage and 3.5" W.C. Max. for 2nd stage. Here are some pics below. You may notice the "hi" and "Lo" gold screws for seperate independent adjustment of 1st stage and 2nd stage in picture 1.

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Old 12-27-2008, 10:08 PM   #35
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How to confirm 2nd stage burner working?


Yea, the humidifier bypass being open, give a false temp rise.
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Old 12-27-2008, 10:10 PM   #36
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How to confirm 2nd stage burner working?


Although they are independant adjustments.
When you change one, it influences the other.

Don't forget to pull the hose off the gas valve, and remove teh burner box cover plate.
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Old 12-27-2008, 10:17 PM   #37
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How to confirm 2nd stage burner working?


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Although they are independant adjustments.
When you change one, it influences the other.

Don't forget to pull the hose off the gas valve, and remove teh burner box cover plate.
Ok, thanks.

I have a real non-pro question for you.

Why can't I just adjust the screws ~ 1/2 turn at a time, then close the unit up, cut her on and recheck the temp rise and also re-time the gas meter to see the impact of the adjustment (since I don't have the pressure gauge yet)?

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Old 12-27-2008, 10:23 PM   #38
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How to confirm 2nd stage burner working?


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Don't forget to pull the hose off the gas valve, and remove teh burner box cover plate.
My installation instructions states that I should pull the hose at the "T" and then "T" in a manometer....but it also states I do not need to pull the burner box cover plate for this model unless I plan to adjust the flame sensor, hot surface igniter, or main burner orifices..

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Last edited by key1cc; 12-27-2008 at 10:37 PM.
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Old 12-28-2008, 04:51 AM   #39
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How to confirm 2nd stage burner working?


If you get a dual port manometer, you don't need to pull the cover, if you tee in.

Doing it by checking temp rise and reclocking the meter.

Assumes that the air flow is exactly XXXX CFM, and that the thermometer used is 100% accurate.

Reclocking the meter is good. But, you don't know the true BTU content of the gas.

If the CFM is slightly lower, and the thermometer reads high temps higher then they are, then the gas pressure would still be low.

The difference between 1325CFM and 1265CFM is roughly 2F at 61,750BTUs output.

Even VS motor CFMs can be off compared to the factory chart/listing.
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Old 12-28-2008, 07:12 AM   #40
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How to confirm 2nd stage burner working?


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Originally Posted by beenthere View Post
If you get a dual port manometer, you don't need to pull the cover, if you tee in.

Doing it by checking temp rise and reclocking the meter.

Assumes that the air flow is exactly XXXX CFM, and that the thermometer used is 100% accurate.

Reclocking the meter is good. But, you don't know the true BTU content of the gas.

If the CFM is slightly lower, and the thermometer reads high temps higher then they are, then the gas pressure would still be low.

The difference between 1325CFM and 1265CFM is roughly 2F at 61,750BTUs output.

Even VS motor CFMs can be off compared to the factory chart/listing.
Thanks,
Makes sense.
I'll order the manometer through the net.

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Old 12-28-2008, 07:21 AM   #41
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How to confirm 2nd stage burner working?


Also,
It is interesting that the pressure max is 1.7" for stage 1 regardless of the gas heat value. If I set it to 1.7" the final BTU's will still depend on the heat value of the gas.

Question: If the manifold pressure turns out to be low say around 1.4"....what is wrong with adjusting it to say 1.9 or 2.0 (instead of the stated max of 1.7) to get even more BTU's for more efficiency (in stage 1 only) as long as my temp-rise does not exceed the 65F max?

Is this something "Jim Davis" would promote?

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Old 12-28-2008, 08:59 AM   #42
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How to confirm 2nd stage burner working?


I believe he would. But, he would be using an annalyzer to check other things also.

One of the problems is that next month. The BTU content could be higher then this month.
So you would have a much hotter heat exchanger. And may be above allowable temp rise.

Next, is that the inducer only moves so much air and gas through the cells in first stage. You would end up with poor combustion.
High CO, low CO2, and low O2. Giving you incomplete combustion.

Meaning, although you inreased BTU output. You had to increase BTU input to an amount that your only at maybe 87% to 88% efficient.

So your input may be 74,750, to get 65,000. (86.9% efficient)

Next. The top of the heat exchanger would begin to over heat.
If it failed. Trane would be able to see the heat distortion. And could void warranty on it.

Even if its within temp rise. The burner end of the cells, will get hotter then they should.

The manufacturers, know what a over heated HX looks like.

Keep in mind, that mod furnaces vary both the inducer speed and blower speed with the gas input, to avoid this problem.
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Old 12-28-2008, 09:23 AM   #43
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How to confirm 2nd stage burner working?


"Turning" those screws is a very precise process. May only need 1/16-1/8 of a turn to make a BIG difference. Has to be done with a manometer. After you turn the screw you need to put the cap back on and then check the reading, or put your thumb over the screw port. There is no packing around the screw and pressure may leak past it and affect the reading. Good thing you have some Pro's here to walk you thru it. Soon you will know more than some of the hackers out there. This is one of the 2 manometers I use. Has a great magnet on the back to hold it to the furnace housing. http://www.ueitest.com/product-em200.html
The other one is this one. More expensive but incredibly accurate and fits in small places.http://www.etool.ca/RENDER/1/11/3041/10955.html
Good Luck

Last edited by yuri; 12-28-2008 at 09:27 AM.
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Old 12-28-2008, 09:49 PM   #44
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How to confirm 2nd stage burner working?


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"Turning" those screws is a very precise process. May only need 1/16-1/8 of a turn to make a BIG difference. Has to be done with a manometer. After you turn the screw you need to put the cap back on and then check the reading, or put your thumb over the screw port. There is no packing around the screw and pressure may leak past it and affect the reading. Good thing you have some Pro's here to walk you thru it. Soon you will know more than some of the hackers out there. This is one of the 2 manometers I use. Has a great magnet on the back to hold it to the furnace housing. http://www.ueitest.com/product-em200.html
The other one is this one. More expensive but incredibly accurate and fits in small places.http://www.etool.ca/RENDER/1/11/3041/10955.html
Good Luck
Thanks for sharing. The 1st one is listed at $153 on amazon.com and the 2nd one list the price as ~$232. You are correct they are expensive for someone not currently in the trade. However, I look at it this way. I saved at least 3 thousand bucks by not purchasing the 10 year labor warranty from the hacks that installed my system. It's a long story that I shared on another site but basically, I had wiring issues, equipment oversized, static pressure issues, leaks, etc. My system already comes with a 10 year parts warranty. The installer wanted an additional $1000 bucks for a 10 year labor warranty and it would only remain valid if I paid them $200+ bucks every year to "maintainence" my system. That totals over $3000 bucks for the ten year period! Why would I pay these hacks that kind of loot, when they could not even get the initial install right, nor correct the problems? Thanks to sites like this and help from knowledgeble pro's like yourself and Beenthere (among others) I have learned quite a bit and already have a pretty good understanding of my system. A few hundred bucks for tools and spending time on the net for knowledge is a small price to pay from my vantage point.

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Old 12-28-2008, 09:58 PM   #45
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How to confirm 2nd stage burner working?


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I believe he would. But, he would be using an annalyzer to check other things also.

One of the problems is that next month. The BTU content could be higher then this month.......

.....Next, is that the inducer only moves so much air and gas through the cells in first stage. You would end up with poor combustion......
Gotcha.

Thanks for the feedback.

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