I just moved into a new house, which has central heating and a/c, with the a/c unit on the ground on the side of the house. Above the unit is a small makeshift wooden “awning”, with planks nailed into the fence on one side and supported by two posts on the other. It’s high enough that I don’t think it’s causing an airflow issue, but I’d rather remove it anyway, if it won’t cause any problems. I’ve never really seen anything like this before, though I wouldn’t know if it’s commonplace or not.
The top side of the unit is the exhaust. If there’s nothing over the unit, stuff will fall on it. So if I dismantle this wooden shelter thing, could my unit be damaged from all the leaves, seeds, pine needles, etc. getting in there? Google only gives me results about shading it from the sun (with most saying not to bother), but I’m not concerned about that.
Unless the previous owner had a reason for putting it there (other than ‘it should be covered’), then no. They are designed to be outside. Some people like to keep them in the shade, and that could be the reason, but even with the sun on it, it should still be fine.
Leaves aren’t really going to get in to it and rain won’t hurt it (in fact, it can help).
If it were me, unless I could see some obvious reason to leave it, I’d tear it down.
My WAG is that someone was trying to keep it in the shade.
And, FTR, it’s certainly not common place, unless it’s a regional thing.
Just to reiterate, the condenser is, by design, okay to be outdoors and totally exposed to the elements.
I had a replacement a/c installed 2 years ago and per the specs, there should be no obstruction above the outside unit lower than 6’. If your “awning” is within that 6’ range, I would remove it to increase air circulation.
I’ve read that direct sun only reduces the performance of the A/C by about 2-3%. What’s really important is the temperature of the air that it’s sucking through the coils, and that the airflow isn’t obstructed. So being on the shaded side of the house, or under a large tree canopy is a good thing. If it’s on a huge black membrane roof or expansive black asphalt driveway, then shading it from the sun won’t help because that small patch of shade won’t cool the surrounding air.
And in my experience, it has to get really hot out before you start to notice reduced cooling.
I have 3 roof top compressors at work and I don’t start noticing the temp in my coolers or freezers going up until it’s at least 90F outside. When it gets that hot, sometimes I’ll put a sprinkler (or direct a hose) on the coils and it works just fine.
If you were to do this all day, ever day, you’d end up with other issues, like scale or mineral build up on the coils, but doing it for an hour or two a few times a year isn’t going to cause a problem and will greatly increase the amount of heat that can be pulled out of the building/cooler/freezer.
Personally, I don’t think that’s really worth the work for a house unless your having problems, but at work I have to maintain a certain temp because they have food in them.
Well, by the time you see reduced cooling you’re already using a good bit more electricity just to maintain capacity. What happens as outdoor temperature goes up (or airflow is restricted) is that the pressure in the system has to increase in order for the refrigerant to condense at the higher ambient temperatures. Higher pressure means the compressor motor uses more power, and it also increases strain on said compressor because of the greater pressure delta between the high-side (condenser) and low-side (evaporator). That’s how an a/c unit in an enclosed space, with blocked coils, or in a very hot environment can “burn out” in a short period of time. The compressor motor overheats and fails under high load.
I did some testing once with a window unit plugged into a watt meter. When it was 75 degrees outside it used about 800 watts. At 90 degrees it used over 1,000 watts. Also, regardless of the outside temperature, the highest fan speed always used the least power because the increased draw from the fan was offset by the lower condensing pressure and reduced compressor load.
Agree with all the above. It’s much more important to make sure you hose off the cooling fins a couple of times a year to get all the dust, spiderwebs and other crap off of them. Dirty fins=reduced efficiency and poorer cooling.
And don’t use a pressure washer.
One of the HVAC people I watch, from time to time, on youtube suggested never getting a condensing unit that has a decorative grate or louvers on it, like this. His reason being that when the fins aren’t exposed, they never get cleaned off by the rain.
Well yes, if it gets blocked by leaves it won’t work. For that reason I seldom see a top-exhaust unit except on top of a building, and the rare exceptions have explanations like “beside a commercial building with a regular maintenance schedule and a light roof” or “built by a commercial builder building his own house using office-building techniques”.
And are not under trees.
Does it look like that will be a problem in it’s present location?
Most of the condenser units I see are top exhaust, because otherwise the airstream has to be deflected to the side which adds resistance. Sure stuff will fall on the top, but it gets blown off whenever the unit comes on. Maybe a leaf or a few pine needles will get wedged in there, but they’re irrelevant. Even little twigs don’t seem to last long.
As for the “decorative” shrouds, I don’t think they’re that big of a problem. They protect the coils from getting dinged by lawnmowers or kids playing ball or any number of other things. They’re also a first line of defense against leaves or other debris that could clog the coils. Granted, things like cottonwood seeds would likely go right through, but I doubt rain would ever be sufficient to wash off bare coils considering how strong a jet of water it takes to dislodge most debris.
The shroud does make washing the coils very difficult, and it basically has to be removed to access them. I remember that being the case in my house growing up. We had a Trane whose coil wasn’t the typical fin/tube setup. The tubes instead had what looked like metal brushes around them, sort of like big pipe cleaners (is there a term for this?). I don’t know if it was easier/cheaper to manufacture, or if it gave better thermal transfer, but it would look awful if left exposed and even then it looks very difficult to clean properly. Here’s basically the same unit: https://www.oneprojectcloser.com/cleaning-you-outdoor-air-conditioning-coil-trane-unit-example/ I think I remember seeing something like that on a very old window a/c unit too.
A lot of it also depends on location and how much they’re used. At my house, I’ve never had to clean my coils. I check them regularly and they’re always fine. At work, my outdoor (and indoor for that matter) have to be cleaned quite a bit. The indoor ones, I probably clean anywhere from once a month to two or three times a year, but they run 24 hours a day, the outdoor ones need to be cleaned a few times a year.
My fridge at home has that type of coil. I figure it’s probably cheaper to manufacturer, doesn’t gather dirt and dust and really never needs to be cleaned since they don’t have fins with narrow spaces to trap debris.
As far as the pros and cons of a ‘decorative’ panel on the outside unit, what I said came from an HVAC youtuber and it seemed to be a throwaway comment when he was a bit frustrated over some dirty coils. I can’t find the clip right now. He does have a video on why he doesn’t like those covers, but it’s not the specific clip I was looking for.
On the other had, self contained heat pumps set out side of the house in the ones I have had it is best to build a roof over them with about 4-5 feet of clearance.
Since they have to work year round a snow buildup or super heavy rain is not good for the unit nor it’s operation. Leaves and twigs are real efficiency killers with them.
I have never had a heat & air professional say to not roof over an outside self contained unit.
So, 3-4 data points from here.
It is surprising how many people do not know if their unit is self contained or not.
Mine have always been in an all electric situation.
My Mom keeps a fabric/waterproof cover over hers when not in use. Drives me nuts. I really worry she’s gonna turn it on and forget about the cover probably destroying it or at least popping some breakers. Maybe cause a fire. This is one thing that she absolutely won’t budge on.
I have seen some people have a vinyl cover for the outside unit for the winter, to prevent ice getting between the fins and doing damage; but the majority of people don’t do this and I’ve never heard of problems. (I don’t do it).
Slight hijack, but I have also heard you’re not supposed to turn off the 30 A circuit breaker to the AC unit in the winter. Reason being… there’s a small heater in the oil reservoir that keeps the oil from freezing. Again, just something I heard. Not sure what the straight dope is on this.
What difference does it make that it’s a “self-contained” unit? Just like leaves and sticks, snow won’t accumulate over the fan because it will blow it away. It could accumulate on the top of the rest of the unit, but so what? I’ve never heard anyone say heavy rain was a problem either. Yeah it can be a bit noisy, but only if it’s a heat pump and near freezing can I see rain being any factor at all.
Speaking of heat pumps, having the unit elevated off the ground is a benefit. For one it keeps it above accumulating snow, but it also helps the water drain away when defrosting. Around here (Cincinnati) I see most new houses have their outdoor units sitting on a couple of posts cantilevered out from the foundation wall, a good foot or two off the ground. This isn’t really heat pump territory, but I suspect even for just an a/c unit it prevents damage from lawnmowers and keeps out grass clippings and leaves.
I’m sure this is different from model to model, but many have a thermal overload breaker that should trip and reset a little while later, not that I would suggest relying on it. If she’s been doing this since forever, she’s probably not going to forget to remove it. However, there should be a shutoff right next to the condenser. Turning it off there would be a good way to remember to pull the cover since you’ll have to go over to it in spring to flip it back on.
I don’t claim to know everything about HVAC, but I’ve only seen heaters on commercial units for freezers and coolers.
The oil won’t freeze, that’s not the issue. Freon* migrates to the coldest place (and lowest pressure) part of the system. If all your freon is sitting in the compressor, it’s going to cause problems with the oil. If it’s all stacked up in the suction line, the compressor is going to slug the next time it turns on.
I know my walk in freezer has a crankcase heater. In times where it’s been shut down for days, in the dead of winter, we’ve turned the heater on for a while before turning the compressor back on. Some of my coolers have a heater wrapped around the accumulator, but that may be to evaporate off some of the liquid. I believe some of them have a heater wrapped around the compressor as well.
Lastly, as I look around on the internet, I see that it’s common to have a heater built into a residential AC compressor. I’m not sure, however, if it’s necessary to have it on all winter or if it’s just meant to prevent migration while the unit is cycling on and off during the cooling season. Many commercial compressors (even air conditioners) run year round. A restaurant, for example, may very well have their AC on even through it’s 20F outside.
*Freon=refrigerant, I always trip over that word and freon is easier to type a bunch of times.
The purpose of the crankcase heater is to prevent refrigerant from condensing inside the compressor, and to keep the refrigerant separate from the oil. Since liquid is basically un-compressable, a “slug” of liquid refrigerant going into the compressor can break the piston, or at the very least dramatically increase wear on the compressor.
The oil used in the system is soluble in liquid refrigerant but not vapor. When the oil is dissolved in the liquid refrigerant it loses most of its lubricating effect. Normally, the oil is just sort of pushed along through the piping by the fast moving vapor. So in actuality there’s some small bit of “liquid” going through the compressor, but it’s more of an atomized spray or trickle along with the refrigerant vapor.
Anyway, the point of the heater is to prevent damage to a cold system when starting up. Even if the compressor can handle the slug of liquid refrigerant, with the oil dissolved in it, the bearings and pistons wouldn’t be properly lubricated for potentially several minutes and thousands of rotations.
It looks like most crankcase heaters use anywhere from 30-100 watts, which can add up to a couple tens of dollars over the off season. If you want to shut down over the winter, best practice seems to be to reconnect power 24 hours before starting the system up again.