metlmunchr
do you install heat pumps/ AC units for a living?
21 years in the business full time plus another 6 years part time during breaks from school. Primarily in commercial and institutional (schools, hospitals, university buildings, etc) rather than residential, but the principles are the same across the board.
I have been ask by who in a previous ?
by 3 people that I know that has been in business for 10 -40 years
no intension of blocking the air!
what I asked about was recommended by the 3 people that I know that do this for a living. minimum3" from the unit and NO top
This isn't an experience related issue. It is 100% related to knowledge of heat transfer principles, and that's not something that gets into the brain via hvac installation/maintenance experience. Experience says I'm standing here at this unit in the sun and its hot as hell, so some good shade would have to make this unit operate a lot more efficiently. Science says that's not the case.
If you google 'shading of air cooled condensers' you'll find this has been studied multiple times with the results always the same. Not worthwhile. Ambient air temperature, and not sun exposure, is the primary influence on efficiency. While the air in a shaded area may be cooler, the large quantity of air handled by the condenser fan quickly evacuates the cooler air which is then replaced by air from other non-shaded areas.
Most studies put the results in a range of 1% to 3%, but the most extensive work was done by a scientist with United Technologies, the owner of Carrier Corp, and another scientist from Kuwait. Their conclusion is that the actual gain is a max of 1%, and in most cases even less than that. If you're spending $100/month for cooling, a 1% saving might pay for one of your 2x4x12's in an entire summer.
These are studies done by groups actually looking for things that can be done to save energy, and not like many of the oil company funded "studies" that have the sole purpose of promoting petroleum products over alternative energy sources. If shading was in fact useful, then Carrier and all the other manufacturers would promote it since it would allow the unit to run under less load with the long term result being less in-warranty compressor failures.
Some of the myths about the benefits of shading come from statements by some government agency about 20 years ago where they made some wild guess that shading would reduce energy use by 10%, with no real data to back up the claim. Another source of misinformation was "This Old House" where someone on that show claimed that shading would reduce energy use by 50%. Once again, just a wild guess, and sorta irresponsible considering its a PBS show.
You can find all sorts of wild claims of savings due to shading on the internet. Some of these are "confirmation bias", which is a situation where a person builds some sort of shade for their unit and then goes on a continuous energy saving kick where the drapes are kept closed, no unnecessary lights are left on, the temperature setpoint is raised by a couple degrees, and so forth, and then all savings are attributed to the shading.
Others are just classic internet wackadoodles whose claims are so outlandish as to be immediately obvious. There's one guy from TX who posts replies to anything he can find that allows public replies. He claims he cools a 1700 sq ft house for $12 to $15 per month with an electric rate of 11 cents per kW-hr via unit shading and gravity attic ventilation. Unfortunately, he has plenty of company in the form of screwballs looking for some sort of internet fame.
If you want to save some real money, look for and correct any leaks in your ductwork. On the outdoor unit, you can save some money by giving the unit a thorough washdown yearly with a cleaner like Mean Green, Simple Green, or a similar solution, and water. A dirty condenser coil does affect efficiency. Avoid the use of acidic purpose made coil cleaning solutions as they're far too strong for any sort of regular use.
