Is a cover for an a/c unit worthwhile in the winter?

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Jadnashua

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Some people cover their a/c units in the winter, some never do. Does it ultimately help to prolong the life of the thing, and if so, is it more likely to be important on some brands/models than others?
 

Cacher_Chick

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I have no personal experience with this but in thinking about it, blowing snow often contains salt and soot residue, so a cover would protect the unit from the increased potential for corrosion that such foreign substances can cause. On the other hand, if a cover is installed which is sealed too well, it could trap moisture during swings in temperature/humidity. A cover that allows airflow through the unit might be a worthwhile investment.
 
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I vaguely recall a good HVAC contractor telling me not to use one of these covers, but I don't remember why clearly. I think it was a matter of condensation being trapped in the unit's wiring and fan resulting in earlier failure of these external components. If it was left open, liquid moisture would not be trapped inside for months like it could be with the cover. I didn't plan to cover mine so I didn't give it another thought.

I did shut off the crankcase heater in my dual stage unit during winter by flipping the breaker. The CCH for that unit was there to prevent flooded starts in heat pump mode but was wired up even for AC only installs. For dual stage this was a 40W heater for each compressor that kicked in below 60 F as memory served. I didn't see any reason to burn 80W continuous and the HVAC contractor confirmed that it was okay to shut it down as long as I gave it 24 hours on before starting up when AC weather returned. (I did measure/confirm the draw before and after turning it off.)
 

WorthFlorida

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There is not a manufacture that even suggest to cover the condenser unit. The only ones who do are cover manufactures.
 

Dana

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At my house we have received 5 feet of snow in the past 10 days, which isn't a super-rare condition here (way more than once per decade, but not every year). If you let thing pack up with snow over a New England winter subsequent freeze/thaw cycles can potentially separate the fins from the coils. I dig the thing out whenever snow drifts cover it, and always at least cover the top, to keep it from getting filled up from the inside. YMMV.
 

DonL

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Covering because of snow would be a good thing.

Around here leaves can be a problem. Also dogs pissing on the coil.

If you have a/c where it snows you may be spoiled.
 

Dana

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Southern New England maritime climates have real cooling loads, often dominated by the latent load. The 1% outside design temp in my zip code is a whopping 83F, but with 30 design grains at 50%, which is comparable to the latent load in Austin or San Antonio.

The central air at my house is ridiculously oversized for the load (5 tons for a 2400' house that is mostly in the shade after 2PM), apparently necessary by the size of the refrigeration coil in the hydro-air handler somebody installed that still serves a heating zone. It's not worth ripping it out, but it's not how I would have done it. The central AC runs maybe 20 hours/year, and the latent loads are managed primarily by a 70-pint room dehumidifier in the basement of this moderately tight house. A 3/4 ton mini-split would do a better job of handling the cooling loads at this house, but it's not worth the investment given the ridiculously low sensible load.
 

DonL

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How much water do you get from the dehumidifier ?

I think a dehumidifier is the way to go, instead of using a central AC unit to dehumidify.
 
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The central air at my house is ridiculously oversized for the load (5 tons for a 2400' house that is mostly in the shade after 2PM), apparently necessary by the size of the refrigeration coil in the hydro-air handler somebody installed that still serves a heating zone. It's not worth ripping it out, but it's not how I would have done it. The central AC runs maybe 20 hours/year, and the latent loads are managed primarily by a 70-pint room dehumidifier in the basement of this moderately tight house. A 3/4 ton mini-split would do a better job of handling the cooling loads at this house, but it's not worth the investment given the ridiculously low sensible load.

Wow, that is way oversized. I had a 4 ton unit (2-stage) for ~2,700 sq. ft. in a climate with high latent heat loads in summer and days that could exceed 105 a dozen times or so in a hot year. That was early 90's home, cathedral ceiling's for half the roof space, not well sealed and insulated (although I did some measurable improvements in both areas). Based on my own measurements of AC consumption vs. temp. over a summer we could have made do with 3 tons after my changes, but that design was tight for 108-110 F which we might have 1-2 days/summer...and I wanted room for any degradation in performance over the expected 15 yr. life of the unit. 3 1/2 ton would have been a great fit, but would not have changed the air handler frame size like a 3 ton would have. Without reducing frame size I couldn't get a smaller ECM blower or a smaller furnace--both of which would have been a better fit 95% of the time.

Newer home now has a 5-ton single stage, but I expect/hope it will be substantially oversized despite being a 3,500 sq. ft. home. Climate here is essentially desert with many 100-105 F days each year and some hotter. Initial impression is that the envelope is tight and well insulated. I've been surprised by how even the temp distribution has been between first and second floors. The ventilation/duct layout is well done compared to most other homes I've been in. But, man-oh-man I miss my ECM blower. This PSC blower draws about twice as much power as my ECM blower did, which is sad because the duct design appears to be relatively low/moderate resistance. It's enough of an issue (from sticking a kill-a-watt meter on it for a month in winter) that I'm going to check into a retrofit.
 

Dana

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How much water do you get from the dehumidifier ?

I think a dehumidifier is the way to go, instead of using a central AC unit to dehumidify.

Since I have it draining into a sump I can't verify the true volume. I've monitored power use on it with a Kill-a-Watt from May-October for at least a couple of years. Limiting the basement to 60% RH is usually enough to keep the upstairs reasonably bounded and keeps mold from taking off in the basement. At that level of dehumidification is uses between 400-600 kwh/year. Working backward from the rated 1.7 liters/kwh that's 680-1020 liters (180-270 gallons) per year.
 

Sino King

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Some people cover their a/c units in the winter, some never do. Does it ultimately help to prolong the life of the thing, and if so, is it more likely to be important on some brands/models than others?
If your unit's fan blows up into the sky, a roof is needed to protect the fan(s).
 

derekbrian

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It is not necessary. AC 's external body is made to withstand harsh weather conditions. If you want to prevent its outer body from dust particles etc, for safety point to view you can cover it.
 

Dana

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Not necessary?

Mine would have been completely full of compacted snow and ice, with the top a full half meter below the top of the snow if it didn't have a cover. The fins on the coils would have been under the mechanical stress of the weight of the melting snowpack. The total snowfall over the worst 10 weeks of winter added up to about 3-3.25 meters. It was not a record snowfall year, nor was it a record snowpack depth. This happens 1-2 times per decade in my area.
 

Reach4

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IMO replies 16 and 17 are maybe preparing legend for future spam. Maybe practicing language. They are unlikely to reply.
 

DonL

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Most people are lucky to have a working AC unit to cover.

Do not forget to remove the cover before operation.

I only did that once. :eek:
 
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