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[merrellroofing]

      I am getting ready to start my install.  Got the pad poured for my CB.

      Dismantled part of my trunkline and my humidifier to access my plenum as it is pretty cramped around my furnace.  The plenum is roughly 19x20 but less than two feet tall.  The A-coil for the A/C sits on a rack on top of the furnace and I have about 4 inches to the top of the plenum. 

      I am assuming the only option is to move the A-coil all the way to the top and try to squeeze a hx under it.  My HVAC buddy said that will hurt the efficiency of the A/C.

      Just looking for help or suggestions.  I will try to post pics when someone more qualified for that job gets home.

[RSI]

I would just put it above. I actually prefer it to be above the A coil than below.
It will hurt the efficiency of the AC a little but that won't have anything to do with where you put it. The only way to avoid that is make it removable. The loss in efficiency isn't usually enough to be worth doing that though.

If you can get at both sides of the plenum, I would use a 19x20 heat exchanger. (or 20x19 depending on which side you need the pipes) The heat exchanger dimensions are of the finned area and most have a 1" flange at each end. Putting the flange out of the airflow keeps the air restriction to a minimum.

[TLuckoski]

I had no room at all in my plenum because of the A coil. So talked to my buddy (hvac guy) who suggested to replace the A coil with a N coil which is shorter. I had him replace it and then put the HX above the N coil  and all is fine AC worked perfect this summer. I did a test run last week on the boiler fired her up work perfect. The wife made me shut it down got alittle warm in the house lol. Hope this helps!

[mikenc]

can u cut existing plenum above a-coil & install rectangular ell then install Hw coil in horiz run just past ell. Just a thought not knowing how much room you have or your duct arrangement.

[Firechaser]

4 inches should be enough to put it above the a coil.

[merrellroofing]

    It will definitely be easier to put it above the A-coil.  But it will be at the top for sure.  I just didn't know how well it will transfer heat being up there where the air can't blow thru it, just blow by it.

[RSI]

You don't have a 4" tall straight section that is 19x20 inches?

[merrellroofing]

   Ya I have 4inches but it will be at the very top, but the trunk comes out a couple inches down from the top so I was worried that the air will just blow right by.  Would it work well enough just being in the plenum and the air not being able to go thru it?

[RSI]

I guess I am picturing it wrong.
You want all the air to go through it.

[oldchenowth]

Knowing full well this may spark an argument, would it work better to put it on the intake side?  I had to do this because of space issues.   Had a HVAC guy build me a special section of cold return wide enough to fit my HX with some angle to rest it on and take up any open area where air could flow around the HX.  Just a suggestion.  I know it is said that it is rough on the blower motor, but so  far so good with mine.

[Bull]

Mine is in the return as well with no issues, I have just run it 1 season so time will tell but so far so good.

[BIGDIESEL20S]

I'm installing mine this week or first of next. I have to put mine in the return (before the fan). Furnace too close to the walls to fit it in the supply.

[willieG]

im not sure if putting it in the return is going to harm anything but you sure do want it after the filter...you don't want your rad acting as the dust collector?

[Firechaser]

I did not realize your trunk came off before the 4 inch space. Sounds like you have to go into the return. I thought I read somewhere that requires an extra switch in your furnace because the incoming air will be hot.

[RSI]

Did you ever get pics?