# AC Coil Location Installation On High Efficiany Furnace



## rstarre (Dec 19, 2008)

I am the Project Supervisor for a government program to install high efficiency furnaces to older homes. The furnaces started getting installed this week I get a call from a home owner this evening saying the hot & cold air is blowing out of the cold air return. I went to the house and sure enough it was. I put a lighter near one of the heating vents and the air was being sucked into the vents instead of blowing out. This is a house with the duct work in the crawl space and should be a downflow unit. The HVAC installer has the AC coil on top of the new furnace connected to the cold air return plenum. The home owner told me her 80% Heil furnace had the coil under the old furnace. On a 92% Bryant gas furnace, shouldn't the ac coil be located in the same place, under the furnace if the duct work is in the crawl space. I called the installer and he was suppose to go to the house this afternoon to see what the problem is. he never showed up. I can't fire him since I have no choice on who the furnace installers are. What ever Union HVAC guys the city sends over to do the installations.


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## beenthere (Mar 5, 2009)

Yes, on a downflow furnace, the A/c coil is under the furnace.

Sounds like some how an up flow furnace got installed, and he put the coil on top like you should for an up flow furnace.


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## TimberlineMD (Jan 15, 2008)

These type gov't projects are 'lowest bidder' driven. The HO got what the city paid for, cheapest bidder.


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## flashheatingand (May 3, 2008)

beenthere said:


> Yes, on a downflow furnace, the A/c coil is under the furnace.
> 
> Sounds like some how an up flow furnace got installed, and he put the coil on top like you should for an up flow furnace.


Out of curiosity, if coils in the return are such a bad thing, why are the majority of gas-packs setup as such?


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## beenthere (Mar 5, 2009)

flashheatingand said:


> Out of curiosity, if coils in the return are such a bad thing, why are the majority of gas-packs setup as such?


Gas packs commonly rust out their heat exchangers, often in less then 10 years. Its easier to make them with the heat exchanger after the coil. Is basically the only reason its done that way.

York in their Affinity line has the heat exchanger before the coil to get a longer life span on the heat exchanger.


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## CompleteW&D (May 28, 2011)

What an idiot. Even if he somehow managed to get an upflow furnace instead of a downflow, how did he not realize all of the supply ducts were in the floor? If he didn't realize it, he's either blind or a moron. And, if he did and installed the wrong furnace anyway, that's even worse. I'm just.... :no:


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## TimelessQuality (Sep 23, 2007)

This thread just cracks me up :laughing::laughing::laughing:


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## flashheatingand (May 3, 2008)

CompleteW&D said:


> What an idiot. Even if he somehow managed to get an upflow furnace instead of a downflow, how did he not realize all of the supply ducts were in the floor? If he didn't realize it, he's either blind or a moron. And, if he did and installed the wrong furnace anyway, that's even worse. I'm just.... :no:


I have seen it happen before. Believe it or not, I haven't made that mistake, but worked for an outfit in which more than one person made that mistake.

Also, it's not the cheapest outfits in town who get those jobs. What kind of irks me, is, these people are getting nice gear, at the tax payers dime. I get that they need a working h.v.a.c. system, but, higher efficiency?


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## flashheatingand (May 3, 2008)

beenthere said:


> Gas packs commonly rust out their heat exchangers, often in less then 10 years. Its easier to make them with the heat exchanger after the coil. Is basically the only reason its done that way.
> 
> York in their Affinity line has the heat exchanger before the coil to get a longer life span on the heat exchanger.


Only dealt with a couple of pre-mature h.e. failures. I would just think it's not too profitable to make a product in which they have warranty issues.


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## CompleteW&D (May 28, 2011)

flashheatingand said:


> I have seen it happen before. Believe it or not, I haven't made that mistake, but worked for an outfit in which more than one person made that mistake.


Wow.... that's incredible. Hey, I _KNOW_ I can make some silly mistakes. But, from guys with as much schooling as they have to carry a license and to not realize what plenum configuration they're looking at when they replaced the thing, like before, I just.... :no: (shake my head)

But hey, at least he put the evaporator coil in the right place. Even though in reality, it was wrong too.


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## beenthere (Mar 5, 2009)

flashheatingand said:


> Only dealt with a couple of pre-mature h.e. failures. I would just think it's not too profitable to make a product in which they have warranty issues.


They make a lot of money selling heat exchangers for the ones that make it past ten years.


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## beenthere (Mar 5, 2009)

flashheatingand said:


> What kind of irks me, is, these people are getting nice gear, at the tax payers dime. I get that they need a working h.v.a.c. system, but, higher efficiency?


Thats so they don't need as much money from the state to heat their homes also. Saves us some tax money, since the heating bill is lower.


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## flashheatingand (May 3, 2008)

CompleteW&D said:


> Wow.... that's incredible. Hey, I _KNOW_ I can make some silly mistakes. But, from guys with as much schooling as they have to carry a license and to not realize what plenum configuration they're looking at when they replaced the thing, like before, I just.... :no: (shake my head)
> 
> But hey, at least he put the evaporator coil in the right place. Even though in reality, it was wrong too.


It's not the contractor who makes the mistake. Heck, (s)he is likely trying to take care of other drama. Sometimes the employee gets done with the installation and, uh-oh. Could have been a snafu at the supply house, who knows. There are a lot of I's to dot, and T's to cross.


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## flashheatingand (May 3, 2008)

beenthere said:


> Thats so they don't need as much money from the state to heat their homes also. Saves us some tax money, since the heating bill is lower.


How much is gas/ therm in PA? Generally, it's the fancy-folk homes that benefit the most from the higher efficiency furnaces. You know, the bigger the house, the bigger the savings.

Then there is the maintenance thing with condensing furnace. If not maintained, those things age awfully quick. At least with a standard furnace, they can take a beating. I just think it's more financially prudent to install a standard efficiency furnace with those who "economically burdened".


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## CompleteW&D (May 28, 2011)

flashheatingand said:


> It's not the contractor who makes the mistake. Heck, (s)he is likely trying to take care of other drama. Sometimes the employee gets done with the installation and, uh-oh. *Could have been a snafu at the supply house, who knows. There are a lot of I's to dot, and T's to cross*.


I totally understand and agree the snafu could have originated anywhere. But when the guy had the new furnace out and see's it's an upflow, and the existing supply plenum is in the floor and the return plenum is coming from directly above, wouldn't that ring a bell with the installer?

Or, even giving him the benefit of the doubt and let's say he mistakes the existing return air plenum as a supply air plenum. Wouldn't he or better yet, _SHOULDN'T_ he question why the return air is coming from the floor directly below the furnace and not via a return air drop like on a regular upflow configuration?

Just sayin.... :whistling


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## beenthere (Mar 5, 2009)

$1.07 per therm.

With a standard condensing furnace. There isn't really much more to go wrong or look at with them, over a 80%er.

Even if it only saves the person an average of 10 bucks a month. In many areas that still comes out to 70 to 80 bucks a year less to heat with. And if they are getting assistance with their heating bill. Its just a little less you and I have to pay for. Or the savings that some agency gets goes to someone else that needs help.

As the demand for nat gas stays low compared to supply. it also helps keep the price down for everyone else.


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## HVAC1000 (Feb 4, 2013)

beenthere said:


> $1.07 per therm.
> 
> With a standard condensing furnace. There isn't really much more to go wrong or look at with them, over a 80%er.
> 
> ...


But won't it take something like >10 years to get that return a due to the cost and installation of the upgraded equipment? I know the savings will be immediate but it will take a while to pay off the the actual installation. Plus what about maintenance costs?


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## flashheatingand (May 3, 2008)

B.T., just saying, if we were to take identical houses, compare receipts including install, utility, & repairs, over a 20 year period. I will bet dollars to donu... er croissants that the 80% model would be the better value.

Fancy-folk house, maybe that's different. But, for po-folk?


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## flashheatingand (May 3, 2008)

beenthere said:


> $1.07 per therm.
> 
> With a standard condensing furnace. There isn't really much more to go wrong or look at with them, over a 80%er.


My good h.v.a.c. buddy from across the river, I beg to differ. If we were to compare two poorly maintained furnaces (80% versus condensing model) over a 15 year period. the condensing unit will be in far worse shape.

That condensate can get ugly.


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## beenthere (Mar 5, 2009)

HVAC1000 said:


> But won't it take something like >10 years to get that return a due to the cost and installation of the upgraded equipment? I know the savings will be immediate but it will take a while to pay off the the actual installation. Plus what about maintenance costs?


Look at the bigger picture. 1,000 furnaces upgraded to condensing furnaces. The state and federal govs paying out less money per year to subsidize heating cost on those 1,000 furnaces. Nat gas price staying lower longer for everyone.


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## beenthere (Mar 5, 2009)

flashheatingand said:


> My good h.v.a.c. buddy from across the river, I beg to differ. If we were to compare two poorly maintained furnaces (80% versus condensing model) over a 15 year period. the condensing unit will be in far worse shape.
> 
> That condensate can get ugly.


Yes, the condensate can get ugly on a condensing furnace if its not set up right.

B vent flue pipes can rust out quickly too on 80%ers if not set up right.

Early version condensing furnaces were a nightmare at times. They have improved alot since the late 80s early 90s.


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## ScipioAfricanus (Sep 13, 2008)

My question is; how deep are your 'crawl spaces' that you can get a down or an up-flow furnace with coil in there?


Andy.


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## HVAC1000 (Feb 4, 2013)

ScipioAfricanus said:


> My question is; how deep are your 'crawl spaces' that you can get a down or an up-flow furnace with coil in there?
> 
> Andy.


They along with everyone put them on a floor that is living space most of the time in a closet then just the duct work is in the crawl space not the unit


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