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Question about an A Coil


hausdok
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Hi All,

Well, today was a banner day. I actually got to see an air conditioner. (I think it is my 5th or 6th in 8 years.)

Anyway, I have a question about this puppy. They mounted the A-coil on the supply side of the furnace beneath a high-efficiency gas unit, with an electronic air filter at the other end of the furnace.

So, I open up the electronic air cleaner to take a look and it looks like it hadn't been cleaned in years. The, when I pull the last pre-filter out, a damned dead deer mouse falls out and damn near gives me a heart attack. (Sorry, I'm like an elephant when it comes to rats and a deer mouse is damned near as big as a rat.)

Anyway, back to the AC - The A coil is mounted on the underside of the furnace with the apex pointed downward! Now, I'm not an AC ace, but seems to me if the A coil is mounted with the apex pointing downward isn't it going to be impossible to clean properly without completely removing it? At least when they're installed with the apex pointed upward into the airstream you can vaccuum the intake side of the coil and remove all of the accumulated crud. With the coil mounted the other way, like a pair of cupped hands, to catch the crud, I should think it would be pretty well clogged up. (Installed in 1989 by the way and never serviced yet.)

Let this puppy run for about half an hour. Ran nice and quiet but only achieved about a 10° split and it dropped the temp in the house (on a 72° day) by only 2 degrees. (I set it much lower.)

What're your thoughts Norm and you other warm climate folks. Okay to have the A coil installed in such a way that you can't even get a vaccuum to the intake side of it? Could a coil clogged with dog hair result in some poor cooling? (They had two hunting dogs.) Or, do you think it has lost its charge after 15 years without any servicing?

ONE TEAM - ONE FIGHT!!! (From where turning on the air conditioner means cranking a window open.)

Mike

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It's not unusual, down here, for an A/C tech to remove the evap. coil in order to take it outside to chemically wash it then re-install it in the unit. Note I said "chemically" wash. Years ago only acid solutions were used now there are also alkaline solutions available. Sometimes only plain water from a garden hose is used. As to the low TD if the coil is obstructed with dirt or animal hair you would expect a high TD due to the fact that the air hangs on the coil longer. The CFM will be reduced. I suspect the system in under charged. If an "A" coil is installed upside down does it become a "V" coil?

NORM SAGE

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As Norm stated, the only proper way to clean a evap. coil is to remove and wash.

Was this a downflow furnace Mike?

When an A coil is installed on a upflow the condensate drips from the top of the coil to the condensate drain pan. If this were installed upside down really don't see how it would work. Something doesn't sound right about that installation. I would suggest calling the manufacture about this one. I'm off to do a Radon test but I'll see what I can dig up.

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With the "A" coil installed upside down it can be a problem with the condensate. On the coil when installed properly you will find a drain channel that runs around the base of the unit that collects and directs the condensation into the drain pan. I would bet that condensation is pooling in the apex of the "A" coil when it is upside down.

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I've never seen one set up that way, but I agree with your instincts about the high crud-catching potential. When I find a nasty one I always recommend not accepting "cleaned in place" to my clients, though some do anyway. I think there's a significant difference between chemical cleaning and plain vaccuuming. I tell clients it's like hosing off your filty car without taking a brush or sponge to it, it really doesn't get clean, just clean-er. I would think the coil would be quicker to reaccumulate crud because of it, but I don't know that.

On the dog hair / lost charge, it could be either or both.

Brian G.

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Mike - On downflow furnaces, the cooling coil (A-coil or slab) is mounted below while the filter would be on the top. Are you sure its an upflow furnace and not a downflow.

If its for sure an upflow, its installed wrong -I saw one about 1 year ago in a "No-Codes Zone" outside KC where they did a similar boo-boo and installed the A-Coil on its side in a horizontal furnace - owner and cousin bought the equipment and proudly installed it by themselves. Cooled like crap and the condensate pan was in an upright position so it caught nothing. They'd put a plastic rubbermaid pan under the unit with a garden hose to dispose of the condensate.

Dan

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Hi Dan,

No, it's a downflow. I just had a brain fart. Look at the time I made that post. My head kept bouncing off the keyboard and waking me up. I finally dragged my chubby butt into the sack at 0330hrs.. Out the door again at 0730 for the morning job.

I.F.,

It was a Fraser-Johnson Mod G/CM0305A. To answer your question about AC here - it probably gets hot enough for A/C for a few hours of one or two days of the year. When we do see A/C units, they've seen so little use and are so old they should probably be classified as antiques.

Thanks for your responses everyone. Neither the furnace nor the A/C had been looked at since 1996 and the furnace was a hi-eff Payne unit that was leaking condensate all over the place. It was easy to refer it to an HVAC guy for cleaning and repairs as necessary.

ONE TEAM - ONE FIGHT!!!

Mike

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No Terry,

It was leaking exhaust condensate from the furnace when the heat was on. When the A/C was turned on, no condensate came out of that puppy at all. I'm guessing that drain was stopped up with rat feces or something. Didn't really care, just referred it off. Was curious about the coil though, cuz with the amount of stuff that was clogging up the air filter, I'm betting the inside of that A (V) coil is similarly nasty.

ONE TEAM - ONE FIGHT!!!

Mike

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