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You're blocking 300-500 W of solar radiation on a heat exchanger that runs 20-100% of the day. So yeah you're definitely going to get some improvements. Most notably it will run less often because it isn't dealing with the excess heat.
AC units SHOULD be designed for 100% duty cycle. But we all know that nothing is really capable of that - even industrial stuff. So if your shade reduces the duty cycle by a few percent, you might increase the longevity of the unit by an order of magnitude.
Interesting. I should see how much sun my units get.
This is interesting. Gut says that it does increase efficiency. Thing I'm questioning is by how much?
Anybody got numbers or a good educated guesstimate?
https://www.aceee.org/files/proceedings/2002/data/papers/SS02_Panel1_Paper24.pdf
Shading the compressor can help but it can also hurt.
Those units can draw enormous amounts of air. Unless the shading covers a very wide area around the compressor, it's likely to mostly pull in air that wasn't shaded and is still at normal ambient temperature.
If the shading obstructs airflow, it can reduce the efficiency of the unit.
Nice source! Thank you kindly.
Planting trees and shrubs close by a condenser may actually reduce system efficiency due to impedance of effective air movement. We conclude that any savings produced by localized AC condenser shading are quite modest (<3%) and that the risk of interrupting airflow to the condenser may outweigh shading considerations. The preferred strategy may be a long-term one: locating AC condensers in an unobstructed location on the shaded north side of buildings and depending on extensive site and neighborhood-level landscaping to lower localized air temperatures.
Tracks with the gut feeling. Shade will only marginally improve efficiency but constricting flow definitely hurts. Units are best installed on the North/Northeast sides of houses in the northern hemisphere.
If your unit is a heat pump, are you then paying for that savings in the winter when it doesn't benefit from any solar warmth to help heat your house? If so, I wonder if it is a relatively balanced outcome or if one of the seasons has a bigger impact. I imagine it depends in part on which season is more extreme in your area.
I would think so. Another factor would be dropping leaves in the fall and winter so less shade, a good thing, in this case.
Not going to give an educated guesstimate, but I do know our ac unit is in full shade of trees, with not much greenery around. It is probably 20 years old. We were told, ten years ago by a repair man, it was close to kicking the bucket, yet it's still going.
My neighbor, has the same unit, newer, leas than ten years old unit, in full sun with bittersweet growing all around it. Last summer they spent half the time trying to fix it, and this year I saw them install window units..
I'm guess, it helps to have it shadded with no plant debris. Purely anecdotal.
Knock on wood oh boy..
Have you been able to quantify how much more efficient your unit is because of the shade?
I have an emporia energy meter. While I can't answer your question exactly, I have sprayed mine with a hose during the hottest part of the day and watched the power usage drop a decent amount. So I imagine as long as the shade wasn't too expensive it'll pay for itself.
Sprayed it down with the hose again. Pic added showing energy usage drop. Doesn't last long from water, but does show it not working as hard when cooler.
Thank you for that visual! And for the new item to research for my home (the meter). 😁
I just want to say that I heart you. Like a lot. 💙
Sadly there are just too many variables in play. Many other changes have been made to help keep costs down such as different thermostat settings, extra insulation, and duct sealing. It does all add up to quite a bit of savings.
I reckon at least three
Boy I'll tell you what, 3 is alot.
I doubt it will make it more efficient. The air it sucks in is still the same temperature.
It might help with longevity of the device itself though, as it doesn’t stand in direct sunlight.
By keeping the sun off it, that helps with keeping the equipment cool which the radiator is part of so there's less heat the fins have to dissipate no?
There's no radiator, it's a heat exchanger.
You have two sections in your heat exchanger. One part wants the cooling agent cold so it can effectively imterchange heat from your room into the cooling liquid. The other part wants the cooling agent hotter than the air outside so it can effectively dissipate the heat to the outside. To achieve that the liquid gets compressed. On the cold side it gets cooled with airflow.
I don't think sunlight will change anything significant in that mechanism.
I think it’ll have an effect. If you think of the cross section of the piping in the condenser (radiator in the outside unit shown in photo), you have heat trying to transfer from the fluid on the inside diameter, through the pipe wall, then to the air surrounding the outer diameter.
Heat has to flow from hot to cold, so ideally you have a gradient from hot to cold going from inside to outside.
But suppose the sun intensely heats that pipe wall and it ends up higher than either fluid on either side of it. Now you’ve got heat flowing from the wall to both inside and outside.
Not saying that ever happens, but every degree warmer that the pipe wall is, is a slow down in the heat transfer rate. Less of a gradient for the heat flow.
...I hate the be the one to tell you this but there are two radiators in a heat pump. The condenser and the evaporator are both evaporators.
I have mine under some trees. It’s shaded in the summer and in the sun in the winter, which helps because it’s also a heat pump
I'm curious why you rehang it every year and don't just install a retractable awning. Hell, putting some smaller retractable shades over the windows, especially the sunnier ones, would probably also save you a chunk of change on those bills.
Snow weighs quite a lot! So it must come down after a/c season is over. This was $20 4-5 years ago. I wish retractable shades were in the budget, that would be awesome.
And your HOA just lets you?
My neighborhood is just too dull to have one I guess. Although once per month the city workers come and pick up leaves and sticks if you place them by the curb, which is pretty exciting.
Easy there, chief. Remember where we are right now.
It’s a sad reality when people assume having an HOA is a given.
Feel bad for people subjected to it but I’d never purchase a property under the thumb of an HOA. Sucks how ubiquitous they have become.
And you can’t legally stop her!
Not all HOAs are bad... mine pretty much only exists to take care of our neighborhood pool, they've even loosened some of the few restrictions that had been in place since the 70s (restrictions on the type of fencing or sheds has been lifted). And it tends to run with a flat budget so our rates are very low for the area.
I'm glad it's working out for you, but fuck if I'm about to pay some self appointment group to tell me what kind of fence or shed is unacceptable for me to own on my own property.
If I want to plop down a shopping container on my own front lawn, anyone who doesn't like it can kick rocks.
And that's why I'm glad there are properties without an HOA because I don't want to have to see the shit you put on your front lawn.
For now.
The fun thing about HOA’s is that they can change and are absolutely dynamic. You never know when Karen’s crew is going to come into power.
Oh, they also changed the bylaws so that further changes to the bylaws require 75% approval from all homeowners in the neighborhood. Karen's crew is going to have to do a lot of work if they want to make any significant changes.
IIRC, my AC guy said the vertical throw of those units is far higher than that, I wonder if that translates into it sucking in more of it's own air (less efficient, higher cost)? Then again, UV seems to destroy everthing...
This is what I came up with. I'm not seeing any heating of the siding it's hard to tell on the sail as it's in direct sun. Also the unit is just under the corner of the sail so air can definitely get up and around. There's about F10* difference between the siding in direct sun and the condenser.
I doubt it. That's quite far and it's open so there's plenty of room for it to spread out. You wouldn't want part of your building to be in the air stream because the air from the condensing unit would heat it up, but it's fine if the tarp gets warm.
Same goes for heat pumps, a little shade can prolong their life and increase effectiveness.
If you're hot, they're hot!
