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-   -   New furnace this winter, now freezing ac coil. (http://www.diychatroom.com/f17/new-furnace-winter-now-freezing-ac-coil-150338/)

robsmale 07-15-2012 12:43 PM

New furnace this winter, now freezing ac coil.
 
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My central ac is definitely old, but has worked no problem until this summer. Over the winter I had a three-stage Bryant Evolution put in. I live in a three bedroom rambler.

What is happening is that water is leaking onto the floor underneath where the blower motor resides. The ac works, but as I feel it starting to not work efficiently, I get "Clean or replace air filter" warnings on my thermostat control. I had been using MERV12 over the winter with no problems. So I switched to MERV8. Still having the problem. I went around and made sure all the dampers were open. They were. Then I start thinking that it is a dirty ("A"-frame style) evaporator coil or the condensation drain hose, hole in the drip pan or something like that. The "tent" of the A-frame is sealed on both sides and I would have to take off more screws than I would necessarily dare to, as it does not appear to be just an access panel. Freon was checked last summer (I could maintain 78 degrees but no lower and now this year I was struggling with 82 degrees, as the coil would begin to accumulate ice).

Here is the new bit of info that just came to light. Any time I have looked at the coil, I only took off the panel on the "back" of the unit (the side without the send/return freon lines or drain hose.

When I came to take off the panel with the hoses running into it, I removed the metallic duct tape that the furnace installers used to seal a big 1" gap where the top of furnace is larger than the bottom of the ductwork where the ac coil resides. They don't match and it leaves a "ledge" just above where the furnace burner manifolds reside. When I took the tape off, there was a lot of condensation underneath it. My question is, could this ledge be providing a non-drained area for enough condensation to build up, drop down onto the blower motor, get blown up to the coil and freeze on it? I have it set so the AC motor is always on high when the AC unit is running.

Also, what is the usual "fix" an installer should follow when things don't match like that? Three of the four sides match, but again, this fourth side is about an inch larger on the furnace side than the existing duct they had to join with and they just taped it up.

JJboy 07-15-2012 12:57 PM

You need to check if the drain line is clogged. You must install a flow safety switch to shutdown your system when the drain line will get clog.

You can use Aluminum Foil Tape and mastic to fix this gap.

robsmale 07-15-2012 01:26 PM

Thanks for the reply. The gap was fixed by the furnace installers with aluminum foil tape. The pic is after I took that off. Drain line was clear.

The bigger problem I just discovered is that the drip tray for the coil is rusted through all over the place. Time to call in the pros for a new coil unit. : (

hvac5646 07-15-2012 02:08 PM

cha-ching$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$

robsmale 07-15-2012 02:54 PM

Getting the whole system replaced. They will be here tomorrow. 15 seer 2 ton Carrier installed for $2500 (after $280 efficiency rebate from power company).

I believe that is what I paid for my whole car!

Cha-ching is right. Seems like a fair enough price though, I guess. It is through a company that five different people in the neighborhood endorse.

hvac5646 07-15-2012 05:25 PM

does that assume you have a VS motor, or is it doing 15 seer on its own?

robsmale 07-15-2012 06:23 PM

Interesting question that it didn't occur to me to ask at the time. I assumed it is 15 SEER on its own because I thought my VS motor was supposed to always run on high while the AC was running. I'll have to ask tomorrow.

robsmale 07-15-2012 07:22 PM

Carrier 24ACB3

http://www.residential.carrier.com/p...formance.shtml

robsmale 07-15-2012 07:30 PM

My mistake. Just talked to sales. It is a much better model.

24ANB6 from the Infinity series.

http://www.residential.carrier.com/p...infinity.shtml

Mr.HVAC 07-15-2012 11:09 PM

I don't know, but someone can correct me if I wrong. It looks like they used rubber hose as condensation line? It's ok with a pump, but isn't that a bad idea for condensate line? Also, I hate it when someone build a plenum between the A-Coil and Furnace. How hard is it to raise the A-Coil down, or even if you have to extend the suction/liquid line and rebuild the plenum on top instead? Robsyale, where is that rubber line connected to the A-Coil going out to?

robsmale 07-15-2012 11:20 PM

Rubber joiner to some kind of flexible pvc to a pump. That was all the old setup from before I bought the house. 18 year old Coleman setup. I figure I got my money's worth. Tomorrow they are installing a unit with the correct sized plenum. Why is it bad to fabricate a plenum to fit with the right proportions?

Mr.HVAC 07-17-2012 02:31 AM

Quote:

Originally Posted by robsmale (Post 966705)
Rubber joiner to some kind of flexible pvc to a pump. That was all the old setup from before I bought the house. 18 year old Coleman setup. I figure I got my money's worth. Tomorrow they are installing a unit with the correct sized plenum. Why is it bad to fabricate a plenum to fit with the right proportions?


It's better if the evap coil sits above the furnace than some thin sheetmetal. It was designed that way

robsmale 07-17-2012 02:37 AM

I bit the bullet and had a whole new Carrier Infinity system put in. HOLY COW IS IT QUIET! I got 22 years out of the old Coleman. Props to that system.

Evap coil is above the furnace. They did a good job and fabricated a plenum to fit correctly.


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