# Confirming correct gas pressure for new furnace



## key1cc (Nov 21, 2008)

Here is the gas flow conversion chart that came with my unit


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## key1cc (Nov 21, 2008)

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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## hvaclover (Oct 2, 2008)

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.:laughing:

Sorry... celebrating early...oops.. just fell off my chair and spilled my drink (Hicop)


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## key1cc (Nov 21, 2008)

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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## hvaclover (Oct 2, 2008)

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...:thumbsup:


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## mikey48 (Dec 6, 2007)

Happy New Year hvaclover


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## beenthere (Oct 11, 2008)

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. 
(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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## yuri (Nov 29, 2008)

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:thumbup:


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## hvaclover (Oct 2, 2008)

mikey48 said:


> Happy New Year hvaclover



Happy new year mikey


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## key1cc (Nov 21, 2008)

yuri said:


> .........So what is the point of going thru all this?.....


You sound like my wife :laughing:

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 :scooter: 

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 :wink:

Key1


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## hvaclover (Oct 2, 2008)

key1cc said:


> You sound like my wife :laughing:
> 
> She asks me the same thing...
> 
> ...


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!:thumbup:


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## yuri (Nov 29, 2008)

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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## hvaclover (Oct 2, 2008)

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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## key1cc (Nov 21, 2008)

Any recomendations for a good combustion analyzer? 

Key1


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## beenthere (Oct 11, 2008)

Any of the Bacharachs.

Starting price, is 500 bucks.


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## key1cc (Nov 21, 2008)

beenthere said:


> Any of the Bacharachs.
> 
> Starting price, is 500 bucks.


The Fyrite Tech 60 measures CO, O2 and stack temp.

Is that sufficient? or do I need something that measures additional gases as well?
See link below

Key1

http://www.bacharach-inc.com/fyrite-tech.htm


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## key1cc (Nov 21, 2008)

*500 bucks!!!*

With that kind of loot I would have to run a few static pressures in the neighborhood to get my money back :wink:

Key


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## beenthere (Oct 11, 2008)

I have the Tech60.
Works fine.

Like most digitals, it does a calc to determine CO2, instead of actually measuring it.

Thats not a real problem.

Yea, for a one time use, its a bit much.


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## key1cc (Nov 21, 2008)

key1cc said:


> With that kind of loot I would have to run a few static pressures in the neighborhood to get my money back :wink:
> 
> Key


Just found the same model for $399.00 :no: ...I'll keep looking 
http://cgi.ebay.com/BACHARACH-FYRITE-60-COMBUSTION-ANALYZER-HVAC-BRAND-NEW_W0QQitemZ160307815693QQcmdZViewItemQQptZBI_HVAC?hash=item160307815693&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A15%7C39%3A1%7C240%3A1318
Key1


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## beenthere (Oct 11, 2008)

Thats a good price.


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## key1cc (Nov 21, 2008)

*Temp rise*

My ultimate goal is to get the maximum efficiency out of my system.
It has been suggested to me that I can improve efficiency by simply increasing my Temp Rise (from 45 to 62).

I like this idea because I can increase the temp rise by slowing my blower.....which in turn lowers my already high static pressure so I get multiple gains. One thing I am unsure of is if I lower the blower speed from the current 1180 CFM's to the lowest setting of 900 CFM's......will that be sufficient airflow to still heat my home? Even though the air temp will be 17 degrees hotter :furious:. I look forward to testing all of that tomorrow.
stay tuned :detective:

Time for me to get some shut eye :sleep1:

Key


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## beenthere (Oct 11, 2008)

The amount of air flow a room really needs, varies with the outdoor temps, the set temp of the stat, and the amount of BTU's in the air.

1180CFM, 45°F temp rise=57,348BTUs.
900CFM, at 62°F temp rise=60,264BTUs.
That would be a 5% increase.

My guess, is that if you slow the air flow to 900CFM, you'll have a temp rise of 59°F(+or-2%).Varies with thermometer accuracy.

Thats my prediction.


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## key1cc (Nov 21, 2008)

I took the advice of another pro and checked multiple places for temp rise. I found a location a little hotter at 47F so I am using that new location (in a main trunk right after the plenum) as my base line as that is the hottest air coming out of my unit.

So my new starting baseline is 47F and ~1180 CFMs.
Initially, I dropped the blower speed to 900 CFMs and the temp rise jumped to 64F which is a little to close to my 65 max upper limit.
So I set the blower to the next lowest speed of 1000CFMs. The temp rise was a reasonable 57.5F. I will see tonight when the outside temp drops to 21F if this new lower airflow will heat my home. 

Additional side benefits of the lower airflow include my static pressure dropping from 0.65 on heat to 0.48 and my wattage draw dropping from 365 to 260.

When I get my new toys I will check the efficiencies :thumbsup:

Key1


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## beenthere (Oct 11, 2008)

For actually doing efficiency test to see if your improving, or decreasing efficiency, when making CFM adjustments.

You need to take readings in multiply places.
As you increase or decrease air flow. You change the pattern(even changes across the heat exchanger).
So you could get more air flow in one area then another. And your temp reading will be off some.

EG:
1180CFM temp rise 48=61,171BTUs.
1180CFM temp rise 47=59,896BTUs.
Difference of 1,275 BTUs

When adjusting manifold pressure only. 
The air flow pattern doesn't change, so you can use one test area.
As the temp rise will be the same increment

Generally, the temp in the trunk line is best to use. Since the air has mixed, so you don't get fooled into a false air temp. 

Your trying to find the mean/average temp of the air. All 1180, 1000, or what ever CFM of it. Not just a few 100 CFM of it.


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## key1cc (Nov 21, 2008)

beenthere said:


> For actually doing efficiency test to see if your improving, or decreasing efficiency, when making CFM adjustments.
> 
> You need to take readings in multiply places.
> As you increase or decrease air flow. You change the pattern(even changes across the heat exchanger).
> ...


Thanks as always for the additional insight. I'm expecting the manometer Wednesday. Not sure if I can afford the combustion meter yet :whistling2:.

For all, the reduced air flow worked great. My home was succesfully heated when outdoor temp dropped to 21F. Static pressure is now down (0.48) under nameplate value :yes:. 

Key1


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## yuri (Nov 29, 2008)

Can never have too many toys/meters. LOL. Probably sounds quieter now that the static pressure/velocity is within specs.


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## key1cc (Nov 21, 2008)

yuri said:


> Can never have too many toys/meters. LOL. Probably sounds quieter now that the static pressure/velocity is within specs.


Can barely here it running unless I stand next to it. Although noise was never an issue since the furnace is in the basement and the return air is dispersed across 6 return grills.

One nice feature of the reduced airflow that finally made my wife support what I am trying to do is that now the air coming from the supply registers feel nice and hot instead of warm.

Key1


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## yuri (Nov 29, 2008)

Now we know who's the Boss. If Mama ain't happy nobody is happy. (according to doc phil).


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## key1cc (Nov 21, 2008)

yuri said:


> Now we know who's the Boss. If Mama ain't happy nobody is happy. (according to doc phil).


You got that right.

Hey tell me what you think of my latest idea. Since I already have a standard wireless outdoor temp sensor upstairs, Rather than continue with redundancy, I am considering moving my new wired outdoor temp sensor that is tapped into my tstat to a location inside the trunk duct about a foot from the plenum so I can easily view temp rise/outlet temperatures at a glance anytime I want. :yes:. Genius or Insanity?

And yes we have already established I have too much time on my hands....:hammer:

Key1


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## key1cc (Nov 21, 2008)

key1cc said:


> I am considering moving my new wired outdoor temp sensor that is tapped into my tstat to a location inside the trunk duct about a foot from the plenum so I can easily view temp rise/outlet temperatures at a glance anytime I want. :yes:.


Nevermind, the max temp of the sensor I have only goes to 120F. I need one that will at least go up to 140F but I do not beleive they exist 

Key1


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## key1cc (Nov 21, 2008)

key1cc said:


> Nevermind, the max temp of the sensor I have only goes to 120F. I need one that will at least go up to 140F but I do not beleive they exist
> 
> Key1


I may have found a duct temp sensor that will work but I am unsure if it is compatible with my Trane Tstat TCONT803 (Honeywell TH8321).

It is at the attached link. 

Does anyone know if it is compatible? Or have any experience with duct temperature monitoring?

Key1

http://www.alibaba.com/product-free/101489179/DTS_12_Sensors_8_00.html


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## yuri (Nov 29, 2008)

When you get thru with this project I have a nice Lennox Harmony III zoning system and a modulating furnace to keep you occupied for a year or so/setting parameters etc.


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## hvaclover (Oct 2, 2008)

yuri said:


> When you get thru with this project I have a nice Lennox Harmony III zoning system and a modulating furnace to keep you occupied for a year or so/setting parameters etc.



He'll need a workin' permit, Eh? No? :laughing:


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## yuri (Nov 29, 2008)

He'll need a divorce lawyer. Still trying do digest all the rich food I had in the last 2 days. Merry Xmas again.


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## key1cc (Nov 21, 2008)

Hey,
My piece of crap manometer came in the mail yesterday. I'm returning it tommorow as it does not work properly :furious:. Fortunately I have the Dwyer Magnehelic guage to check for accuracy. The manometer gives readings that make no sense. According to my new manometer my pressure drop across my filter is only 0.02. Under the same conditions I read 0.1 on the Dwyer guage. Also When I check positive pressure I get 0.29 or 0.39 or 0.14, etc...it is not consistant where the Dwyer stays flate at 0.24. also when I pull the SP tip out it reads the ambiant air at 0.29 until I reset it. What a piece of crap. 

They wanted a 25% restocking fee so rather than pay that we worked out a deal where they would send me another model from a different manufacturer and refund the difference of my loot.

Now I'm waiting another week or so before I can check and adjust my manifold pressures. I'd better find something else to do before I go into HVAC withdrawal. :laughing:

Key1


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## hvaclover (Oct 2, 2008)

yuri said:


> He'll need a divorce lawyer. Still trying do digest all the rich food I had in the last 2 days. Merry Xmas again.


Eastern Orthodox and Old Calendar Yuri?


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## yuri (Nov 29, 2008)

Not exactly sure. Ukrainian Catholic (Dad)/ they follow the Greek Orthodox Calendar. As a kid I never complained about 2 Christmases. Follows the position of the moon etc. Easter varies with that I believe.


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## yuri (Nov 29, 2008)

For Key1cc: Some light reading for you; http://tech.lennoxintl.com/PDFs/505023l.pdf. This is what I play with when I get bored. I`ll have a pop quiz for you on it tomorrow. LOL.


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## hvaclover (Oct 2, 2008)

yuri said:


> Not exactly sure. Ukrainian Catholic (Dad)/ they follow the Greek Orthodox Calendar. As a kid I never complained about 2 Christmases. Follows the position of the moon etc. Easter varies with that I believe.



Main stream Greek orthodox is the regular date.

Eastern Orthodox is old calendar like you are celebrating..


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## key1cc (Nov 21, 2008)

yuri said:


> For Key1cc: Some light reading for you; http://tech.lennoxintl.com/PDFs/505023l.pdf. This is what I play with when I get bored. I`ll have a pop quiz for you on it tomorrow. LOL.


How about the pdf of that nice modulating furnace you got :brows:

Key1


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## yuri (Nov 29, 2008)

That unit uses a very complex algorithm to determine the firing rate etc. (Voodoo magic). Way way above the average joe's knowledge. I took a course with Lennox about it. It won't make sense to you or be interesting. I will be installing one with a Harmony III zoning system in the future and will know more about it. Can work as a 3 stage unit also.


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## key1cc (Nov 21, 2008)

Does anyone know where I can find the O2 /CO2, CO, draft, and stack temperatures manufacturer's specifications for the Trane XV95 100k btu furnace? :yes:

Key1


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## kennzz05 (Nov 11, 2008)

hey key have you noticed your post count seems stuck on 99? on another note please tell me that your post count includes answering other peoples questions on other forums and is not soley based on your questions here. heres a thought every time you think about static pressures or btu output or duct sensors for temp rise(are you kidding)go kiss your wife and perhaps show her the love you show your furnace. if you have young kids go read them a book but for christs sake stay the hell out of the basement. can you say o.c.d? sure, i knew you could. dude cmon!
ok let the fleeceing begin...


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## beenthere (Oct 11, 2008)

key1cc said:


> Does anyone know where I can find the O2 /CO2, CO, draft, and stack temperatures manufacturer's specifications for the Trane XV95 100k btu furnace? :yes:
> 
> Key1


You won't find them any where(they don't exist).

And you couldn't duplicate it, if you could find them.

Your house is not a lab(at least not like theirs).


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## key1cc (Nov 21, 2008)

kennzz05 said:


> hey key have you noticed your post count seems stuck on 99? on another note please tell me that your post count includes answering other peoples questions on other forums and is not soley based on your questions here. heres a thought every time you think about static pressures or btu output or duct sensors for temp rise(are you kidding)go kiss your wife and perhaps show her the love you show your furnace. if you have young kids go read them a book but for christs sake stay the hell out of the basement. can you say o.c.d? sure, i knew you could. dude cmon!
> ok let the fleeceing begin...


Wifee has her hobbies....and I have mine.

Key1


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## hvaclover (Oct 2, 2008)

key1cc said:


> Wifee has her hobbies....and I have mine.
> 
> Key1



Aw don't listen to them guys. So far you are almost a Podwan status. OnCE you have learned all the arcana and have mastered the the "Light Pyschrometer " you will be introduced into the Probationary Jedi Ranks.

But you must fight a DARK LORD OF HVAC,  TO PROVE YOUR WORTH.... A SITH MASTER. HIS NAME: DARTH CLOVER!!!!

MWA_HAHAHAHAHAHAHAHAHAHAH:furious:.:laughing:

.....


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## hvaclover (Oct 2, 2008)

key1cc said:


> Wifee has her hobbies....and I have mine.
> 
> Key1



Just an after thought, a song "Who's making love to your old lady, while you were out making love to Hvac?"

Changed up the title a little but this Biz can be so interesting you need tobe careful you aren't neglecting other parts of your.

Luck Key! You coming along fine.:yes:


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## yuri (Nov 29, 2008)

Beenthere is correct. There is nothing you can adjust to change the CO and other readings. I have setup conversion burners etc and you need to be able to adjust the primary and secondary air etc to change those readings. Setup your gas pressures and call it a day. Some new ductwork and a zoning system would be interesting/challenging/stimulating/good group project for us.


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## key1cc (Nov 21, 2008)

Thanks Beenthere and Yuri for that insight. It was my understanding that the combustion should be checked and the CO values should be under 100 ppm and the O2 values between 6 and 9% with 6 being better than 9 (per the great Jim Davis).

As far as wifee goes, she has jumped on the bandwagon and is now pushing me to go to school and get certified as a HVAC'er as a back up in this recessionary environment in case I loose my day job (whatever the hell that is) :laughing:

Key1


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## key1cc (Nov 21, 2008)

hvaclover said:


> "Who's making love to your old lady, while you were out making love to Hvac?"
> 
> :yes:


ROFLMAO 

I will tell her you inquired :lol:

Key1


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## yuri (Nov 29, 2008)

Those figures are used to check for cracked heat exchangers etc. Lennox gives them to us as well. Nothing is adjustable other than the gas pressures. Have fun.


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## Dr Heat (Jan 14, 2009)

key1cc said:


> Wifee has her hobbies....and I have mine.
> 
> Key1


Do her's use double A batteries I just ask cause well do they


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## key1cc (Nov 21, 2008)

as long as I keep taking care of her 3 times a day ......She doesn't care what I do with the rest of my time...Can you say the same :huh::huh:

Key1


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## key1cc (Nov 21, 2008)

Dr Heat said:


> Do her's use double A batteries I just ask cause well do they


Actually the batteries kept running out...had to upgrade to plugin...:biggrin:


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## Dr Heat (Jan 14, 2009)

when you gotta go to gas powered you Know you got a keeper and lets not even talk about Diesel:whistling2:


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## beenthere (Oct 11, 2008)

Key, your just gonna have to go to an NCI course.


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## key1cc (Nov 21, 2008)

beenthere said:


> Key, your just gonna have to go to an NCI course.


Already a member (Just got my January newsletter.)

Are you going to the big Summit in Dallas?

http://www.gotosummit.com/


Key1


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## key1cc (Nov 21, 2008)

beenthere said:


> Key, your just gonna have to go to an NCI course.


My choices are Air Diagnostics & Balancing, Mold Liability and Prevention, or CO/Combustion training.

The Air diagnostics will be in Philly (about an hour drive) in April...

Key1


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## devlon (Jan 23, 2009)

Take your wife's thermometer out of the kitchen draw and check the Temp rise of the furnace before messing with any pressures. The gas pressure setting on most furnaces for natural gas is 3.5" of water colum on high fire with a new air filter. Check the temp Rise and make sure you are with in manufactures specs. Temp rise should be found on one of the stickers insinde of the furnace usually in the burner compartment. Temp rise is suplly air temp (air leaving furnace) ( outside drect line of site but as close to the heat exchanger as possible) minus the reutrn air temp. Instead of buying a meter you will probally never use again. Never set your temp rise to its maximum as your filter clogs or you go from a cheap blue one to a better pleated filter your temp rise will increase. So Don't fix what you think is broken Fix what you know is broken. ( True Jedi Wisdom) Also Look at the way your furnace is burning If you can see the flames with out dismantling your furnace. check the temp. rise If you stand a few feet away from it You should see a nice blue flame with very little yellow at the extreme ouside of the flame. it should have a very very nice blue core. I say stand a few feet back because if you are standing to close stirring up dirt and dust into the air you Will see the flame Flash more yellow as you add dust to the fuel you are burning.


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## devlon (Jan 23, 2009)

sorry about re hashing post i jumped around the post abit


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## beenthere (Oct 11, 2008)

key1cc said:


> Already a member (Just got my January newsletter.)
> 
> Are you going to the big Summit in Dallas?
> 
> ...


Nope.


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## beenthere (Oct 11, 2008)

key1cc said:


> My choices are Air Diagnostics & Balancing, Mold Liability and Prevention, or CO/Combustion training.
> 
> The Air diagnostics will be in Philly (about an hour drive) in April...
> 
> Key1


 
If you go to the combustion course.
You'll learn how to use a ball valve in the intake line of your combustion air.


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## key1cc (Nov 21, 2008)

devlon said:


> Take your wife's thermometer out of the kitchen draw and check the Temp rise of the furnace before messing with any pressures. The gas pressure setting on most furnaces for natural gas is 3.5" of water colum on high fire with a new air filter. Check the temp Rise and make sure you are with in manufactures specs. Temp rise should be found on one of the stickers insinde of the furnace usually in the burner compartment. Temp rise is suplly air temp (air leaving furnace) ( outside drect line of site but as close to the heat exchanger as possible) minus the reutrn air temp. Instead of buying a meter you will probally never use again. Never set your temp rise to its maximum as your filter clogs or you go from a cheap blue one to a better pleated filter your temp rise will increase. So Don't fix what you think is broken Fix what you know is broken. ( True Jedi Wisdom) Also Look at the way your furnace is burning If you can see the flames with out dismantling your furnace. check the temp. rise If you stand a few feet away from it You should see a nice blue flame with very little yellow at the extreme ouside of the flame. it should have a very very nice blue core. I say stand a few feet back because if you are standing to close stirring up dirt and dust into the air you Will see the flame Flash more yellow as you add dust to the fuel you are burning.


Let's see if you are really Jedi.
Question for you.
If my temp rise range is 35-65 and my max nameplate supply temp is 165F and my temp over protection is factory set at 180F.....then what is wrong with having my temp rise at 75 degress when my return air is 70F?

Key1


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## hvaclover (Oct 2, 2008)

Key, Been don't play that.


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## key1cc (Nov 21, 2008)

hvaclover said:


> Key, Been don't play that.


Got it!


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## hvaclover (Oct 2, 2008)

key1cc said:


> Got it!


That Jedi thing is just me being silly.


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## key1cc (Nov 21, 2008)

hvaclover said:


> That Jedi thing is just me being silly.


Is it?

Take a look at the sub-title of the link in post 62 of this thread

Key1


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## hvaclover (Oct 2, 2008)

Coincidence only.


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## beenthere (Oct 11, 2008)

Because the HX would be hotter with a 105° temp rise, then with a 100° return air temp.


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## key1cc (Nov 21, 2008)

Which senerario is harder on the Heat Exchanger A or B and why?

A. If my return air is 60F and my (correctly measured) supply air is 115 then the temp rise is 65 which is the top of my spec.


B. If my return air is 90 and my supply air is 140 then the temp rise is only 50.

Scenario A has a higher temp rise but a lower HX temp of 115. While senario B has a lower temp rise but a higher HX temp of 140.

Which is harder on the HX the larger difference in temperature (temp rise) or a higher absolute temperature?

Key1 :detective:


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## Dr Heat (Jan 14, 2009)

ok here is a question I have always wondered about it may be a bit off topic but not as far as you may think.

If you are walking down the street in a boat with six flat tires how many pancakes does it take to shingle a dog house?


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## hvaclover (Oct 2, 2008)

Dr Heat said:


> ok here is a question I have always wondered about it may be a bit off topic but not as far as you may think.
> 
> If you are walking down the street in a boat with six flat tires how many pancakes does it take to shingle a dog house?


I don't think Key gets the joke or the implications of his question to Been.


Key you made a lot of progress,irregardless, don't disrespect the man.


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## key1cc (Nov 21, 2008)

hvaclover said:


> I don't think Key gets the joke or the implications of his question to Been.
> 
> 
> Key you made a lot of progress,irregardless, don't disrespect the man.


My question is to all.

And I have nothing but respect for Been.

Where did that come from??

Key1


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## hvaclover (Oct 2, 2008)

key1cc said:


> My question is to all.
> 
> And I have nothing but respect for Been.
> 
> ...


Looked like you were continuing the conversation to me.
It's expected and usual to redirect the question /conversation if you are addressing the whole board.


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## beenthere (Oct 11, 2008)

The heat exchangers temp, is always higher then the air temp(presuming the furnace is running, and working correctly  ).

The surface temp of the HX increases more then 10° when you increase the temp rise 10°.

2 forms of heat come from a hot air furnace(actually 3).

A. Conduction.
B. Radiant.
C. Convection.

The lower temp rise, means the HX temp is cooler so that you are receiving less heat(BTUs) from radiant heat(internal jacket temp is cooler), and more heat through conduction(air contact with HX surface).

The higher temp rise means your getting more heat(BTUs) from radiant(internal jacket temp is much higher), and less from conduction(air contact with HX surface). Which means the HX temp is higher. Although still providing the same amount of heat(BTUs) to the air. (To an extent, after you slow the air so much, you actually lose heat transfer efficiency).

You may not have an electric range.

But, if you ever get a chance, do a little experiement.

Fill a kettle/pot with cold water, set it down near the range.
Turn a burner to high. Wait and watch for it's element to glow red.
After its glowing red, put the pot/kettle of water on it for a minute or 2.

Then remove it and look at the burner/element. 
Its not glowing red anymore.

Without the pot/kettle on it, over 90% of its heat was in the form of radiant.
With the pot/kettle on it, over 90% of its heat was from conduction.

Same amount of heat BTU wise.

But, which way was the element actually hotter.
And which way do you think is more harmfull to the elecment, as far as shortening its life span.

A furnace's heat exchanger life span, and performance, is a balance of maintaining the right proportion of radiant and conduction heat transfer.

At 100° return air temp, and 65° temp rise, the heat exchanger, is cooler then at 70° return temp, and 95° rise.


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## hvaclover (Oct 2, 2008)

Ok, so Been took it in stride. Just shows you what a class act he is.


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## veesubotee (Nov 22, 2008)

beenthere said:


> The heat exchangers temp, is always higher then the air temp(presuming the furnace is running, and working correctly  ).
> 
> The surface temp of the HX increases more then 10° when you increase the temp rise 10°.
> 
> ...


Been, great explanation.

V


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## key1cc (Nov 21, 2008)

beenthere said:


> The heat exchangers temp, is always higher then the air temp(presuming the furnace is running, and working correctly  ).
> 
> The surface temp of the HX increases more then 10° when you increase the temp rise 10°.
> 
> ...


 
:notworthy: I said it before and I'll say it again. Beenthere is in a class by himself :notworthy:

Thanks again Beenthere for furthering my production of additional brain cells. I really enjoy learning about this stuff and I will not be deterred by those that would rather I spent my free time as they do....watching re-runs of "Seinfield".....:thumbsup: 
Key1


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## key1cc (Nov 21, 2008)

hvaclover said:


> Looked like you were continuing the conversation to me.
> It's expected and usual to redirect the question /conversation if you are addressing the whole board.


 
No harm...no foul..

Key1


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## key1cc (Nov 21, 2008)

hvaclover said:


> Ok, so Been took it in stride. Just shows you what a class act he is.


I still have no idea what you are talking about.....an actually I probally don't want to know.

Remember the glass can always be perceived as half full or half empty. It is up to the interpreter to decide which. 

Key1


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## beenthere (Oct 11, 2008)

key1cc said:


> :notworthy: I said it before and I'll say it again. Beenthere is in a class by himself :notworthy:
> 
> Thanks again Beenthere for furthering my production of additional brain cells. I really enjoy learning about this stuff and I will not be deterred by those that would rather I spent my free time as they do....watching re-runs of "Seinfield".....:thumbsup:
> Key1


Wait till you get my $7,800.00 bill for first Semester Tuition. :laughing:


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## key1cc (Nov 21, 2008)

beenthere said:


> Wait till you get my $7,800.00 bill for first Semester Tuition. :laughing:


 
:smartass: Check is in the mail ....:whistling2:


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## yuri (Nov 29, 2008)

Plus $6800 for Yuri. LOL. Should have never given out that meter clocking info. LOL:laughing:


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## kennzz05 (Nov 11, 2008)

zzzzzzzzzzzzzzzzzzzzzzzzzzzz


































































































































zzzzzzzzzzzzzzzzzzzz














































































zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz


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## hvaclover (Oct 2, 2008)

key1cc said:


> I still have no idea what you are talking about.....an actually I probally don't want to know.
> 
> Remember the glass can always be perceived as half full or half empty. It is up to the interpreter to decide which.
> 
> Key1



Half way? You sayin' the new president is half white?:huh:


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## hvaclover (Oct 2, 2008)

kennzz05 said:


> zzzzzzzzzzzzzzzzzzzzzzzzzzzz
> 
> 
> 
> ...


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## drdon51 (Jan 14, 2009)

I disagree with zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz-----------This was better than reading my playboy-LOL--seriously


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## key1cc (Nov 21, 2008)

drdon51 said:


> I disagree with zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz-----------This was better than reading my playboy-LOL--seriously


Good! it's going to get much better if I ever get my tools. :hammer:

In the mean time a link for your continued reading pleasures.

http://www.helpinaflash.com/House-Projects/Heat-Transfer.cfm

For those who prefer to read this thread as a sleep inducer rather than count sheep....:yawn:
Glad we can save you a few pennies off your sleeping pills... :sleeping:

Key1


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