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Old 12-31-2008, 05:13 PM   #1
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Confirming correct gas pressure for new furnace


Rather than continue hijacking that other gents thread I decided to start my own thread on confirming correct gas BTU's.

To save you some catch up reading here is the summary.

I have a new XV95 2-stage Trane furnace 100,000 BTU's with an XL15i 4 ton AC for a 2800 sq. ft. house in NJ.

One of the pro's indicated that you could tell if the amount of gas being delivered to your furnace has been set up correctly by simply letting it run and "timing" how long it takes for the gas meter outside your home to make one revolution on the "1 CFH" dial.

I have completed this task and called my local Utility company to get the required "Heating Value" factor.

Here are the results from my measurements using the 2CPH dial (from the chart that came with my furnace.....see next post):

Stage 1, 120 seconds = 60,000 btu input X 1037 heating value =62,220
Stage 2, 81 seconds = 89,000 BTU input x 1037 heating value = 92,293.

I am still short on BTUs since stage 1 input is supposed to be 65k and stage two 95K.

My Installers never made any gas adjustments so I have ordered the manometer recomended by Yuri to do it myself.

That is the history.

Key1

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Old 12-31-2008, 05:22 PM   #2
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Confirming correct gas pressure for new furnace


Here is the gas flow conversion chart that came with my unit
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Confirming correct gas pressure for new furnace-gas-flow.jpg  

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Old 12-31-2008, 05:30 PM   #3
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Confirming correct gas pressure for new furnace


On a pro forum today, someone suggested that to truly know your BTU output you must measure the flue temperature and perform flue gas analysis using one of the portable meters (yet another toy ).

Anyone here on the DIY site have any experience with that.....and care to share any insight?

Thanks

Key1
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Old 12-31-2008, 06:34 PM   #4
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Confirming correct gas pressure for new furnace


Yep. The guys with the toy are the Jedi Knights of HVAC.

Takes a lot of education and first hand experience to wield a Light Analyzer.
It's a delicate balance of just skirting the the Darkside of delicately balanced air flow.

More so is i the never ending battle for just the right degree NG inches of WC pressure.

Sorry... celebrating early...oops.. just fell off my chair and spilled my drink (Hicop)
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Old 12-31-2008, 06:50 PM   #5
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Confirming correct gas pressure for new furnace


I'm thinking about the model in this link.

Any of you jedi knights familiar with it ...or have another recomendation?

http://www.fieldpiece.com/combustion_check.html

Key1
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Old 12-31-2008, 07:15 PM   #6
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Confirming correct gas pressure for new furnace


I have just felt a ripple in the Force.

Every body meeting up at Yoda's hut.

Vader is bringing a stripper and Skywalker is going to entertain the Lady Jedi's.

I'm going there now..see ya after I sober up...
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Old 12-31-2008, 07:26 PM   #7
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Confirming correct gas pressure for new furnace


Happy New Year hvaclover
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Old 01-01-2009, 02:52 AM   #8
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Confirming correct gas pressure for new furnace


It doesn't do CO, so its not really a good meter.

If it tells you that the O2 is at 7.6%, and the CO2 is at 9%, you won't know if thats good or not.

The CO reading tells you more then the calculated CO2 does.

Next. Other then adjusting gas pressure. What are you going to adjust to make the deifference between 93%, and 95% efficient.

But, it would be a neat toy for you.

We can never have enough toys. :D
(Thats why I have 4 digital manometers, plus a u tube)

PS: Don't confuse combustion efficiency, and heat transfer efficieny.
They are 2 different things.
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Old 01-01-2009, 08:24 AM   #9
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Confirming correct gas pressure for new furnace


As much as it is worth setting up your unit properly it's efficiency will always vary according to how the gas valve modulates due to the draft thru the heat exchanger which is a function of the venting which is related to outside air temp/density/barometric presssure/wind blowing at the pipes etc etc. So what is the point of going thru all this? You set it and it varies anyway. As beenthere said earlier, next week the gas htg value can change so its seems like an awful lot of effort for a theoretical result. You are going to find it challenging enough to work with the manometer and set the gas pressure. Heck, I haven't even cleaned the flame sensor on my unit yet (waiting to see how many yrs it can go B4 it acts up).
Happy New Year Everyone
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Old 01-01-2009, 09:09 AM   #10
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Confirming correct gas pressure for new furnace


Quote:
Originally Posted by mikey48 View Post
Happy New Year hvaclover

Happy new year mikey
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Old 01-01-2009, 10:12 AM   #11
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Quote:
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.........So what is the point of going thru all this?.....
You sound like my wife

She asks me the same thing...

The answer?

It has become my new hobby...... like one big toy with the potential of additional little toys

It beats the hell out of sitting around watching re-runs of "King of Queens". It exercises my mind to try and extend my current capabilities and its nice when that mind exercise interests me.
HVAC interest me.
She also asked why don't I go to school and get certified.
My response?

HVAC in the comfort of my basement interest me, not in someone's hot attic, or with their wild pitbulls running around the house.

I finally conclude by telling her, I've had interests in the past that eventually faded away, I'm sure this will also

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Old 01-01-2009, 10:21 AM   #12
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Confirming correct gas pressure for new furnace


Quote:
Originally Posted by key1cc View Post
You sound like my wife

She asks me the same thing...

The answer?

It has become my new hobby...... like one big toy with the potential of additional little toys

It beats the hell out of sitting around watching re-runs of "King of Queens". It exercises my mind to try and extend my current capabilities and its nice when that mind exercise interests me.
HVAC interest me.
She also asked why don't I go to school and get certified.
My response?

HVAC in the comfort of my basement interest me, not in someone's hot attic, or with their wild pitbulls running around the house.

I finally conclude by telling her, I've had interests in the past that eventually faded away, I'm sure this will also

Key1
Bwahahahahahah...

You gonna be like me! I have a garage full of automotive tools all mounted and professionally displayed.

Problem is I won't touch a car to repair. But I got all the tools for it.

Good luck there Key, once you get bite by the hvac bug you may find your self doing service calls!
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Old 01-01-2009, 10:58 AM   #13
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Confirming correct gas pressure for new furnace


After you have fixed a few units next to someones stinkin cat litter box the "fun" wears off. Did have a couple 4 yrs olds poke me with their light sabers last week. Cute kids. As long as you don't lose interest in the wife you should be okay. Lawyers are expensive I hear. You may want to set the gas pressure and meter clock it daily for a couple of weeks to see the trend. Or buy a treadmill and get some real exercise.

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Old 01-01-2009, 02:28 PM   #14
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Confirming correct gas pressure for new furnace


And don't forget the Friendly horny Pittibulls who never bite anybody as they back you into a corner with lust in their eyes. REmember to just let them finish. And then walk away slowly.
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Old 01-02-2009, 07:04 PM   #15
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Confirming correct gas pressure for new furnace


Any recomendations for a good combustion analyzer?

Key1

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