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Old 07-15-2013, 11:01 AM   #1
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AC Insulation Experiment

Took the cap off AC to clean and inspect for bugs and dust. I noticed that there was no insulation at all around the cap or the duct that brings cool air into the inside. So I got some of the insulation that was used to insulate my sons garague that looks like bubble wrap with foil on one sideI used the spray on glue that is used to glue down the rubber roof that will not melt the insulation. Here are some after photos. Oh if you notice that on the inside of cap I put the foil side pointing toward the out side and the white side to the inside to reflect the heat. You can get this insulation at Lowes or any home improvement store and the glue you can get at most camper parts store. Will let you later how well it works. [ATTACH]Click image for larger version

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Old 07-15-2013, 11:32 AM   #2
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I want to do this!! In their infinite wisdom, my Coach manufacturer painted the AC unit covers BLACK!!

I've noticed that the AC isn't as efficient when the sun is baking the roof!

Please let me know if this makes a difference, if it does... I will definitely do this!

Mal
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Old 07-15-2013, 12:00 PM   #3
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I looked at the white plastic paint, but if this works........
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Old 07-15-2013, 12:43 PM   #4
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That seems to be an excellent idea and mod. Let us know how this works out.
Drat, another thing to add to my list.
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Old 07-15-2013, 02:16 PM   #5
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Outside air doesn't mix with inside air. The air outside is drawn through the condenser to remove heat from the freon. That same freon circulates back into the evaporator, inside the RV and inside air gets cool from the evaporator. I can't see any way insulation added outside could help. In fact, it could cause the unit to overheat by blocking air flow.
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Old 07-15-2013, 02:54 PM   #6
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Outside air doesn't mix with inside air. The air outside is drawn through the condenser to remove heat from the freon. That same freon circulates back into the evaporator, inside the RV and inside air gets cool from the evaporator. I can't see any way insulation added outside could help. In fact, it could cause the unit to overheat by blocking air flow.
Over at HVACfun words it:
Lack of condenser cooling:
Insufficient air or water flow over a condenser will raise the head-side pressure and temperature, and may cause the compressor to run in an overheated condition. It's important to determine that sufficient air or water is available for condenser cooling. In addition to causing potential compressor damage, high head pressures lower the compressor capacity, increase running time and increase power consumption.

Apply that to higher ambient temperatures and you run into the same issue, not to the same extent but it is noticeable.
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Old 07-15-2013, 03:01 PM   #7
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He is not blocking the vents to allow proper airflow... just reducing the amount of radiant heat is entering the AC cover by insulating it.

I agree that blocking the airflow would have a negtive impact, but I don't see how lowering the ambiant temp around the unit within the housing can have an ill-effect?
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Old 07-15-2013, 03:41 PM   #8
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He is not blocking the vents to allow proper airflow... just reducing the amount of radiant heat is entering the AC cover by insulating it.

I agree that blocking the airflow would have a negtive impact, but I don't see how lowering the ambiant temp around the unit within the housing can have an ill-effect?
X2, that was the impression I got too. I think he is insulating the duct work and cover. My covers are also black, so I am interested if this helps.
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Old 07-15-2013, 05:43 PM   #9
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My covers are black don't know why they went to the trouble and expense to paint them when they were white and would reflect heat. I did not cover the coils only the air handling box, that is were the inside air moves over the cooling coils where there shouldn't be any water and also by doing this it should take the chance of water condensation and dripping back inside. The material that I used, I don't think it really has a great R value but it has the reflective foil. I am not a engineer just a country boy with commonsense and some know me as the TU-- oh well you know the story if you were at the NR.
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Old 07-15-2013, 05:45 PM   #10
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Ok... So I peeled off work to do this. I bought a roll of sticky back silver duct insulation from Home Depot. (I'll post a link to the product when I get to a computer). $18.00

It is 95 degrees here with bright sunshine. I keep the coach at 80 degrees so I was able to check the efficiency before and after.

Before the intake temp was 81 and the exhaust was 69 degrees. Not a bad break, 12 degrees. (Checked with a infrared gun)

I pulled the cover and applied the insulation to the underside and front of the cowl, being careful not to block any of the vents. I cleaned the surface with alcohol before i applied.

I also applied the insulation to the cooling box for the inside air. There was already a very thin layer (1/16) of insulation. I cleaned the surfaces and applied the insulation to three sides. The back had styrofoam up against it.

Put the cover back on. Total time about 15 mins.

Back in the coach, intake temp was 80 (I had to lower the thermostat to run the ac), the exhaust was 65. 15degree break now!! I gained 3 degrees.

I imagine this was mostly from wrapping the cold box more so than the cowl underside. Either way 3 degree colder air makes it worth it for me!

Now to do the bedroom AC. I'll take pics when I do that one.

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Old 07-15-2013, 05:46 PM   #11
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OK, so you took pictures of the inside of my AC units. NSS is everywhere. I think the biggest improvement is the piece glued to the top which seals it better. The light weight foam that seals the top probably gets tired and allows air to sneak past. The added insulation helps compress and seal it. I don't think the outside sun makes much difference in any case. While in there be sure to check where wires pass through and seal those. It does not take much to let water bypass the condenser. I do believe it made a small difference on ours. We are in intense heat in the Sacramento Valley and need as much help as possible.

The biggest improvement in overall cooling is modifying the registers inside. Those ductwork systems rob about 50% of the efficiency of our system.
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Old 07-15-2013, 05:48 PM   #12
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Run your fans on High versus Auto when it is extremely hot. If the compressor cycles off you still get the last of the cool air versus letting it just sit there.
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Old 07-15-2013, 07:35 PM   #13
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OK, so you took pictures of the inside of my AC units. NSS is everywhere. I think the biggest improvement is the piece glued to the top which seals it better. The light weight foam that seals the top probably gets tired and allows air to sneak past. The added insulation helps compress and seal it. I don't think the outside sun makes much difference in any case. While in there be sure to check where wires pass through and seal those. It does not take much to let water bypass the condenser. I do believe it made a small difference on ours. We are in intense heat in the Sacramento Valley and need as much help as possible.

The biggest improvement in overall cooling is modifying the registers inside. Those ductwork systems rob about 50% of the efficiency of our system.
YC1, what modifications did you do to your registers?
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Old 07-15-2013, 07:56 PM   #14
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YC1, what modifications did you do to your registers?

A/Cs wont keep MH cool; Are some RVs better insulated?

Go to #18 for pictures. These were less than $10 at a local Osh store.
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