Building shade structure for home ac condenser?

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I live in the Houston Texas area and my house is cooled by a whole house ac. I have an efficient unit but I think that it would run even better if the condensor didn't sit directly under the hot sun in the middle of the day. My thought is that I would build a structure to give it shade. I would be interested in hearing from people who have done this and suggestions of websites for possible designs.
Thanks, Al Kondo
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This is Turtle.
I don't see the great need for this to be done but I have seen it and done it for customer for years with the shade to the condenser and it is very easy to do and does not take any great thinking to do it. You only need to put a one side structure up to shade your condenser and don't need to enclose it. Go out at 1:00 P.M. in the day and stand close to the condenser and put your arms up in the air and shade the condenser at this time. This will be the hieghth of the one sided wall and just have it wide enough to cover the condenser till dark. Now some people prefer a 2 sided wall for looks and that is fine too. You can hide it this away too.
Now building the structure : Use 4 X 4 Lawn timbers for the post and board fencing boards for the cross member to shade with. Most Shade will have to be 6 foot or more to shade properly.
Now a good ideal is to keep the fence atleast 24" from the condenser coil to make sure it plenty of air.
I'm from Louisiana and do HVAC/R for a living , but i too will not object to the shade even when the hvac industry can show you of it's very small savings. It has got to save more than just a small amount like they say.
TURTLE
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I should think you could cut that 24" down to much less (with a suitably lower overall height and less of an overall eyesore) if you arranged for _lots_ of side ventilation.
Ie: don't run the walls to the ground, leave as much of the skirting open as you can.
If you can find (or make) cheap louver panels, use them instead of solid panels.
Etc.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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This is Turtle.
The Manufactor recommend minium 18" but would prefer 24" and so we can just take the installation instruction and throw them out and put as close as you want. Also the 24" is the space to work on that side without taking down the sun block to work on it.
TURTLE
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I'm in NY, where this is less of a concern. YOu'll get an assortment of opinions, but I'm for shading condensors. I don't remember the specs for how far off the top, but figure three feet or so, and open on the sides.
--

Christopher A. Young
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: I live in the Houston Texas area and my house is cooled by a whole : house ac. I have an efficient unit but I think that it would run : even better if the condensor didn't sit directly under the hot sun in : the middle of the day. My thought is that I would build a structure : to give it shade. I would be interested in hearing from people who : have done this and suggestions of websites for possible designs.
FWIW my brother lives in Phoenix and his unit sits on the roof of his house and thats the norm out there.
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Al Kondo wrote:

You'll get a million opinions and tons of pseudo-science.
Or you can examine a well-conducted study:
http://www.fsec.ucf.edu/bldg/pubs/pf302 /
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We conclude that any savings produced by localized AC condenser shading are quite modest (<3%) and that the risk of interrupting air flow 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.
What a conclusion! I notice they only studied one or two adress, and that they concluded not to block air flow.
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Christopher A. Young
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Al Kondo wrote:

I could be wrong, I have not done the numbers, but it would seem to me there would be very little to gain but doing it. The heat gain by the sun has got to be low compared to the heat gain from the coolant.
--
Joseph Meehan

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Take it for what you think it is worth.
A book on my shelf, published when SEER's were lower claims up to a 20% reduction in energy cost when the condenser is sheltered from mid day and late afternoon sun.
Based on what I have read since I would think that high but I throw it out for your consideration.
Colbyt
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This is Turtle.
when I was a ked working on hvac/r stuff in my father's business late 1950's till 1990 the ideal of shading a condenser was a must , but now days all the engineers and tom ,dick, and harry will tell you it make no difference.
Country boy theory : The hotter the condenser coil run or gets the higher the head pressure will run and then will burn more electricity at a higher head pressure. Call me the unknowing but i think it makes a difference.
TURTLE
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I'm with you about the higher temps. The desert dwellers have known this for years -- shade is cooler. AC guys have also known this, that lower head pressure is.... like you say.
--

Christopher A. Young
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Make the top 10 feet above the unit with all sides open. Otherrwise when the discharge air hits the underside of the shade, the air recirculates back through the condensor coil. This costs you more than the savings rou get from the shade. I have seen such shades and walls built around the outdoor units. I have measured air entering the condensors as much as 115 degrees on a 95 degree day. That is a heck of a penalty for shading your unit. Plant a TALL shade tree. It will shade the unit but not recirculate the air.
Stretch
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Shading the condenser will not make the slightest difference, IMHO.
If trees or other shade producing structures provide shade for the house, the house will not get as hot as when the house is subject to full sun. Therefore, substantial savings in energy can be achieved by shading the house.
However, shading a condenser is a totally different story. The cooling efficiency of the condenser is solely dependent on the temperature of the ambient air that is used to carry-off the heat generated by the condenser. A lot of air is pushed through the condenser fins and shading the condenser has no effect on the temperature of this cooling air. Just common sense.
Save your money.
Walter The Happy Iconoclast www.rationality.net

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Must me nice to be you know it all but still have time to answer questions on a news group! Now back up what you say!!!

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I think the report Stormy posted a link to says it all! Nothing like a good study to lay this question to rest. Before we discuss this further, everyone should read the report.
Stretch
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Thanks, chief, but someone else posted the link.
I read the report, they only tried one house, and it sounds like they coulda done a better job designing the shade.
--

Christopher A. Young
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Did the laws of physics change?
Your conclusion that it does not save much may be correct, but your reasoning is incorrect. The sun will cause the condenser and any exposed fins to pick up some heat. The sun has been doing that for many years now. The only question is how much heat is gained and how much can be saved by shading and is there a payback. .
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Edwin,
I couldn't agree more. The savings from shading may be modest, but Walter's statement is poorly worded at best and poor science at its worst. I assume that he just didn't phrase his reply carefully this time.
A unit located in the sun is constantly picking up thermal energy from the sun. That heat negatively impacts AC operating cost, although there are questions about how much.
Imagine 3 AC outdoor units: 1) The first has a steady mist of cold water hitting the entire exterior of the case. The cold water plus the thermal losses from evaporation cool the case considerably. This is an extreme simulation of "negative solar heating." 2) A normal unit located outdoors. 3) A unit with "modest-BTU" flames hitting all four sides. Point four contractor propane heaters (jet engine style) at the 4 sides of the unit. This is an extreme simulation of solar heating. Provide ambient air from a protected source and path so that it is not being impacted by the heaters.
Which unit will operate most efficiently? Obviously, unit #1 which simulates "negative solar radiation." Next is unit #2. Worst is unit #3 which simulates extreme solar radiation.
Situations 1 and 3 above are extremes, but they illustrate the fact that one cannot honestly say that "efficiency of the condenser is solely dependent on the temperature of the ambient air." It may very well be possible to say "direct solar input on the unit is trivial compared to ambient air temperatures", but that is a very different scientific statement.
Personally, I believe that gains from proper shading are modest (1%-10%), but they are still relatively free and may also add cosmetic benefits. I'm hoping to install a new AC system this year and I'll go with the obvious choice - locating the compressor unit on the North side of the house instead of the back (East) of the house. That is quieter, better looking and certainly has to offer some minor but significant energy savings.
Regarding the study on the impact of shading, it is important to remember that this was a small study conducted by a university.
I interact on a continual basis with university professors and I know that some have a lot of common sense and are good at research. I also know that a lot of them don't know their ass from a hole in the ground and are radically out of touch with the real world. I live in a neighborhood full of PhD types and I spend a lot of time helping them get their lawn mowers started in the Spring, adjusting carbs, examining brakes on the car, helping them avoid getting ripped off my mechanics & contractors, etc. I'm no smarter than the regulars on this newsgroup, but I feel like a DIY genius next to many university types.
One engineer on our street didn't understand why the trash collectors aren't allowed to pick up dehumidifiers. When I mentioned freon and the (alleged) destruction of the ozone layer, he said "yes, but that is for refrigerators and air conditioners. A dehumidifier doesn't need freon." Duh. He is currently having problems with his Harley, which now leaks gasoline out of the carb when it is running. The problem started after he had a performance shop "soup up" his bike. I told him that this is a common problem on Harleys after a new camshaft is installed and the factory original manifold is still on the machine. The overlap between intake and exhaust valves has been radically changed and raw gasoline is getting blown back through the short manifold. My overeducated neighbor won't believe that and prefers to believe the mechanics who say "We didn't break your Harley. Give us a blank check and a couple of weeks and we'll fix it."
Sorry about rambling so much. I'm just saying that you shouldn't believe every over-educated nerd out there. And don't automatically accept every university study as gospel.
One additional point - if the air conditioning is derived from a heat pump setup which provides some or all heating in the winter, then I'd suggest installing one of the following: 1) Deciduous plantings which will drop their leaves in the fall and allow solar input on the unit in the Winter. 2) A wooden screen which can be easily removed and stored in the shed over Winter. You don't want solar input in the cooling season; you do want it in the heating season.
Gideon
========
Edwin Pawlowski wrote in message ...

Did the laws of physics change?
Your conclusion that it does not save much may be correct, but your reasoning is incorrect. The sun will cause the condenser and any exposed fins to pick up some heat. The sun has been doing that for many years now. The only question is how much heat is gained and how much can be saved by shading and is there a payback. .
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I moved mine inside a long time ago, where the air conditioning keeps it cool.
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