AC compatibility question

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elm

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Dear DIYers,

Forgive if this is a stupid or trivial question. Hopefully, it's an easy one for many experts here. We recently bought a condo with an in-wall AC units in three different rooms. One of them barely cool, two other ones don't cool at all. All three look dated and beaten up. A friend of mine offered us his used AC units for free if we want them. They were used for no more than few months. They are about the same size as our units although I will need to do exact measurements to confirm but they are different makes and models. However, my friend's units are Window units, not the through wall units like ours.

My question is whether it's possible, and if so not unreasonably difficult, to install the window AC unit into the wall. I understand that some mounting hardware modifications might be needed. I am reasonably handy and even have access to a small machine shop at work.

I would appreciate any advise on whether it is worth to at least try taking my in-wall units out and swap them for window units.

Thank you in advance!
 

Dana

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The through-wall AC units are usually designed to slip in into metal wall-sleeves of standard (or sometimes custom) sizes. As long as the window unit isn't so tall or wide that the hole has to be enlarged, it's usually possible to do a reasonably air-tight installation of a window-unit into a pre-existing wall sleeve. Just make sure the tilt is correct for draining the condensate from the window AC to the outdoors, not onto your floor. Use cut up rigid foam insulation to fill any side & top/bottom gaps between the sleeve & AC housing, and use can-foam to seal the rigid foam (use sheet plastic on the exterior of cabinet of the AC unit to keep the can-foam from gluing it in place.)

On a related note, if you're not on the gas-grid and heating with #2 oil, propane, or electric baseboard, there may be an advantage to replacing the AC units with a heat pump version (called PTHP = "point terminal heat pump") often found in hotels, and using the PTHPs to heat the place whenever it's above 25F. The heat out of a heat pump is substantially cheaper than #2 oil or propane, even at CT style electricity pricing. Somewhere between 20-25F most PTHPs turn off the heat pump and switch-on resistance heating, which is 2.5-3.5x the cost of when it's running in heat pump mode, and more expensive than heating with oil/propane. Current PTHPs often come with scroll compressors are actually pretty quiet compared to reciprocating AC compressors.

A PTHP in heating in heat pump mode delivers between 10,000-12,000 BTU/ per kwh (varies with outdoor temp) which makes 20 cent electricity roughly equivalent in cost to $2/gallon heating oil or $1.50/gallon propane in a zero standby loss, zero distribution loss heating system. That's not a huge discount from current oil pricing, but it's a steep discount from the past 5 year average, and quite a bit cheaper than propane even at current pricing.

If you're heating with natural gas, fuggedaboutit, proceed as planned with the nearly-new AC window shakers.
 

WorthFlorida

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In the winter months you'll need to fashion a cover of sorts with some insulation to keep the drafts down. Another could be power. Those old through the wall units we quite inefficient and most used 220v. The window units are more likely 120v. A little electrical work may be needed. Lastly, depending how tight the fit is, the old units pull air from the rear and discharge the air right back out on the other half. Window units usually pull air from the sides and discharge out the rear. If it's a tight space there may not be enough air flow over the condenser coils.

Wow, Sears still sells through the wall units. I sold many of them at Sears in S. Florida because the century villages built in the 1960's to the 1970's used nothing but these units, cheap to install. If you read the description at the URL below it mentions the wall sleeve, as Dana explained.
http://www.sears.com/frigidaire-a-c...M7742624122?prdNo=33&blockNo=33&blockType=G33
 

Tom Sawyer

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Just frame the opening like you would for a window. Include the jams that will hold the unit.
 

Dana

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Just frame the opening like you would for a window. Include the jams that will hold the unit.

There can be complications with that approach with a condo-association that cares about things that change the appearance on the exterior. If you screw up the flashing & siding and end up with a downstairs neighbor with mold growth in the ceiling it gets even uglier. The safest approach would be to use the existing opening & sleeve & flashing if it is known not to leak.
 
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