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Old 12-03-2008, 01:39 PM   #1
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A coil installation


I am replacing an old lennox furnace with a new 80% Heil and am not sure where the coil should be, on the top or the bottom. It is a downflow furnace and the coil is installed on the top of the old one [the return air side] Is it okay to to install it on the top of the new one? I have read that it should be on the outflow side.

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Old 12-03-2008, 04:18 PM   #2
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Goes underneath. Not supposed to be on top cause condensation will rust out heat exchanger.

You got a lot of modification a head of you....can you post pics? Could give you detailed procedure if I saw what you have.

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Old 12-03-2008, 04:53 PM   #3
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That explains why the burners were rusted out. I have the old furnace out and it was sitting on a 18" high metal base with the duct connected on the side of the base. It's installed in a garage with the duct running under the house and the return in the attic. I dont have pictures yet, but can get some if needed.
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Old 12-03-2008, 04:59 PM   #4
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A coil installation


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That explains why the burners were rusted out. I have the old furnace out and it was sitting on a 18" high metal base with the duct connected on the side of the base. It's installed in a garage with the duct running under the house and the return in the attic. I dont have pictures yet, but can get some if needed.

If the duct is on the side you will have to build the base where the coil sits higher than the side duct opening. Otherwise you won't get any air flow.

I think that is why the old coil was on top. Do you have room above furnace to raise it higher?

You will probably need to custom fab the cold air return.
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Old 12-03-2008, 06:33 PM   #5
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I have room now because the new furnace is about 27" shorter than the old one. Which way would the coil need to face? Flat side to the bottom of the furnace or coned?
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Old 12-03-2008, 06:43 PM   #6
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LOL...I am glad you asked for advice. Flat side down. Didn't the the drain connection give you that clue?
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Old 12-04-2008, 10:35 AM   #7
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I vote for getting help from someone. What grade brazing filler you planning on using? Purging with nitrogen? What vacuum are you going to pull?

Do the dirty work but try to find someone in the know to check it out and connect it.

Just my 2 cents.
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Old 12-04-2008, 11:06 AM   #8
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There have been a few guys who have done their own replacement.

With a little input he'll pull it off.
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Old 12-04-2008, 03:34 PM   #9
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The which side is up on the A coil just had me thinkin the worst I guess.
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Old 12-04-2008, 04:16 PM   #10
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Not as bad as my buddy who first started out.

He was working for me and started to remove the deflector plate off the top of the A coil.

When I asked him why he was removing it (He was a boiler operator and done SOME resi work) he said we didn't need it because it was just a shipping
bracket.


Now THAT is just dumb.
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Old 12-04-2008, 11:02 PM   #11
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What's with all the lennox and heil crap. Jesus, isn't anyone concerned about efficiency, reliability and warranty? In the case of HVAC, yo really do, "get what you pay for" just because a furnace cost $500 bucks, doesn't mean it's a steal. You'll spend some more cash down the line once that warranty's up and all the sudden parts start failing. Happens with almost every fedders and comfort maker. I had a comfort maker the other day, 2 weeks past the warranty, blower blew out the fan relay at the board, needs new motor and board. Can't stress it enough people, pay the extra couple hundred bucks and get a good furnace and A/C. Or don't, I'll gladly come out to your house, for a price, fix the problem, for a price, and depending on the severity of the repair, you may be without heat or A/C until I get the right part. So, how far is the couple hundred bucks gonna spread out over the course of 1 bad repair? Not cocky, just honest. Not all techs are out for your cash, some of us like what we do, but at the same time, our recommendations are just that, most of us have your best interest in mind, mainly because it's fewer recalls for us to have to run. Think about it.
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Old 12-04-2008, 11:07 PM   #12
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Downflow coil is under the furnace *be sure you have the downflow kit for the furnace!!!! A coil should look like an A, not a V, you probably should have gotten an N coil, but, take what you can get. Now, when the installations done, you need to pull a sufficient vacuum on the system, and unless you're certified, don't touch, or in anyway shape or form come into any contact with freon or puron. You mess up and accidentally dump some into the atmosphere, that a 12k fine from the EPA. Just a heads up
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Old 12-05-2008, 04:09 AM   #13
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A coil installation


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Originally Posted by James W. Terwort View Post
I am replacing an old lennox furnace with a new 80% Heil and am not sure where the coil should be, on the top or the bottom. It is a downflow furnace and the coil is installed on the top of the old one [the return air side] Is it okay to to install it on the top of the new one? I have read that it should be on the outflow side.
Ensure to isolate the indoor coil from the outdoor coil by front setting the service valve from the outdoor coil. There is a procedure on some units that you can perform to recover as much refrigerant to the receiver. You will also need a recovery unit to recover all refrigerant in the indoor coil. You might want to hire someone to do this for you. It is illegal to purge refrigerant to the atmosphere, as already mention here. Place a cover on the refrigerant lines to prevent as much moisture and dirt contamination. As mention ensure to pull a good vacuum.I normally perform a triple evacuation to ensure all non condensible gases were removed. If you don't have it already with the new replacement indoor coil, add a thermostatic expansion valve. Good Luck!
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Old 12-05-2008, 09:17 AM   #14
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Downflow coil is under the furnace *be sure you have the downflow kit for the furnace!!!! A coil should look like an A, not a V, you probably should have gotten an N coil, but, take what you can get. Now, when the installations done, you need to pull a sufficient vacuum on the system, and unless you're certified, don't touch, or in anyway shape or form come into any contact with freon or puron. You mess up and accidentally dump some into the atmosphere, that a 12k fine from the EPA. Just a heads up

Lighten up Theo. It's a DIY site not a PRO hvac site.

Help if you can and please do not knock brand. There are plenty of Pros here who use Lennox and Heil to great effect.
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Last edited by hvaclover; 12-23-2008 at 02:32 PM.
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Old 12-23-2008, 01:15 AM   #15
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A coil installation


Hi,

I just bought a vacation mobile home with a down-flow central heat and windows AC units. The furnace is about 30 years but was only used about 10 days a year. It actually passed a carbon monoxide test.

I was thinking about adding an A-coil to the existing furnace and a condenser.

I'm a handyman with electrical background but no experience in HVAC. Although I did several minor repairs in HVAC, but I have never installed one. I really need your help in saving some money$$.. I plan to call in a pro to deal with the vacuum\fillup once I complete the dirty work.

btw.. The furnace blower has a warning label stating "Do not use with an AC system" Would that really be a problem giving that I will be using the system just about 2 days per week.

Any receommendations or assistance you can office to guide me are greatly appreciated. Thanks.. and Merry Christmas everyone!


Last edited by bekind42; 12-23-2008 at 02:14 AM.
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