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Should I cover my air conditioner for winter? It's difficult to find an appropriate cover, but finding a cover for an evaporation cooler is easy (and because they allow for air flow from the outdoors, it makes sense).

See this answer for things to do before winter hits, where it's not clear whether an air conditioner should be covered or not.

I don't want to let water build up inside and given my climate, it will freeze and thaw repeatedly which can be very damaging. On the other hand, I don't want to create a moisture barrier that leads to other problems.

Any official word on this?

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5 Answers 5

up vote 17 down vote accepted

I have never covered mine and this article also seems to recommend not covering it:

Your central air conditioning unit consists of a compressor and condensing unit placed outdoors in a metal housing. These units, built to resist the weather, generally do not need a cover. In fact, covers can cause problems because they trap moisture and create an inviting winter home for small animals.

Professionals who service the units tell me that most of the damage they see in spring was caused by rodents living in the units and chewing on wiring.

If your air conditioner is subject to falling ice or other debris, you could cover its top with a piece of plywood, plastic or metal held in place by a weight.
Reference: http://misterfix-it.com/blog/?page_id=36#cac

They make a great point that a cover would provide a perfect winter home for animals which would cause damage to your air conditioner.

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1  
After talking to a friend in the HVAC business, I found out that sometimes people forget the covers, turn the units on in spring, and wind up with a service call when the unit overheads. –  JYelton Jun 7 '11 at 15:05
2  
Our installer was very explicit in saying nothing more then a piece of plywood with a brick on it should go on the unit, and he said that if I did that to make sure I open the outside disconnect. (I did do that last winter since my unit is right where the icicles usually pile up) –  mwalling Jun 7 '11 at 17:26
    
*Overheats! Doh. –  JYelton Oct 8 '12 at 19:26

I cover mine in the winter using a single unopened trash bag and some duct tape. The bag is the right size to cover just the top and not much of the sides. This allows ventilation on the sides while keeping snow and ice from entering from above. With the duct tape, it's just a strip down each corner and then I run a band of tape around the perimeter of the bag to reduce the risk of it blowing away. I think the important tip that Jeff's link mentions is to not completely seal the unit, but simply prevent damage from above.

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Most people who advocate covering mention that debris, ice, and snow can get into your air conditioner in the winter if it's not covered. Plus it'll end up more weather-beaten if left uncovered.

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Never covered mine in the 31 years I've had it and I live-in upstate New York--brutal winters. no need to cover it.It's designed to be outdoors.Around here there's more damage done in the spring with the cotton wood seeds plugging the condenser.

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It is good to cover the top 1/4 to 1/2 of the air conditioner. This stops moisture from entering through the top and then freezing/thawing repeatedly through the winter. First, although paint technology is very advanced, constant expansion and contraction of painted metal will eventually lead to cracking and this rusting of the metal. Secondly, there are threaded connections between the tubing that goes from the compressor and condenser/evaporator cooling coils. Water can enter these threads and expand and contract eventually causing a leak and thus loss of gas. Covering 1/4 to 1/2 of the unit will keep the interior of the unit under the same temperature/humidity conditions as the outside air. Although this cover will keep the interior of the unit dryer, it will not provide as good a quality of home for critters as if the unit was covered completely. There will still be good ventilation of icy air to make animules look for better digs.

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