On Fri 31 Jul 2009 01:15:03p, Dave told us...
I would have thought that cooling the unit with mist would help, but given the mineral content of our water here, I would never consider it without it going through a softener in addition to filters. I expect that the fins would clog quickly.
On Fri 31 Jul 2009 03:25:48p, Ed Pawlowski told us...
Our A/C system is properly sized for the space being cooled. Even in 118°F temperatures it can maintain any interior temperature we set. My concern was the outside components deteriorating prematurely when exposed to consistently high temperatures. I had hoped that shading the unit would be of some benefit. I was less concerned with heat load and improved performance.
At all previous home and A/C installations, the condenser/compressor unit was in the shade most of the day.
On Fri 31 Jul 2009 08:11:36p, benick told us...
In that case, maybe I'll just stop worrying about it. :-)
This comes up every year on various HVAC sites, the consensus is that it does very little. To put some math to it:
The maximum heat gain from a surface directly facing the sun is about 1000 BTUs per square meter. The condenser has maybe a half meter of surface facing the sun at any time, probably not even that since the sun is overhead during the hottest weather.
You didn't say how large your HVAC is, but let's look at a 4 ton unit. That provides 48,000 BTUs of cooling, and depending on the efficiency, has to transfer approximately 55,000 BTUs of heat into the air. The solar gain of 500 BTUs amounts to less than one percent. So all it does is slightly reduce the amount of subcooling, probably not even measurable with typical instruments.
My experiment was in a rental house I lived for a while. With outside temps 110+ the A/C would never cool the house below 81 until after 7pm. As I said before, the water had no effect.
The A/C unit was built in '97 and IIRC, it was a 2.5 ton 10 SEER on a
1250 sq/ft house. I'd consider that marginal if not inadequate.
Good analysis. I've never seen it explained that way before. I have seen at least one study that was done comparing the identical installations of shaded vs no shade and the conclusion was similar. It made no measurable difference in energy usage.
On Sat 01 Aug 2009 06:46:53a, DT told us...
Thanks, Dennis. This is very interesting information that I didn't know. However, I am less concerned in improving performance (it is more than adequate), than I am in wanting to minimize deterioration from the constant sun exposure.
The house and A/C are both 3 years old. The A/C is a 13 seer 3-1/2 ton unit. It appears to be properly sized for the house.
On Sat 01 Aug 2009 07:25:43a, Dave told us...
I would consider it inadequate if an A/C cannot cool to the desired temperature.
Both our house and A/C are 3 years old. The A/C is 3.5 ton 13 seer, cooling a 1645 aq/ft. house. The house is extremely well insulated. We normally cool to 75° on the weekends and from 5:00 p.m. to 10:00 a.m. during the week. While we're at work we only cool down to 80°. To conserve energy, I would make that 85°, except that we have several indoor pets and aquariums.
Having said that, during "high activity levels" in the house, we often cool down to 70-72°.
Paint the exposed parts with higly-reflective and durable paint.
On Sun 02 Aug 2009 10:24:42a, HeyBub told us...
That may be a viable alternative. Thanks!
Nothing like a dose of glossy white.
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0
f =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0- Hide quoted text -
Living in an area where 110F+ temps are common, why did you go with only a 13 seer unit 3 years ago? I would think the pay back from a higher efficiency unit would be fast and go to putting more money in your pocket than worrying about the effects of outside temps on the life of the cooling eqpt.
Yeah, well, it don't cost much... and if you don't like it, you can paint it back.
You know, thinking on it, maybe that white paint they use on roofs would work. It's made for the action and, heck, it's got to be durable.
On Mon 03 Aug 2009 09:15:16a, HeyBub told us...
I believe that some of those white roof products are supposed to have insulating qualities, too.
Last year I noticed a neighbor resurfacing their roof with one of these white products. They also used the same "paint" to cover their roof- mounted swamp cooler. I should ask if it made a difference.
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