Pimp My Coleman Mach 3 AC

[mstell2]

What are you trying to achieve with this modification?


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[Soga65]

Wow I've got to try this my 1ac Mach 3 on my 831ress struggling to keep kool, in fact at the beach in the heat of the day it doesn't

[Pinn]

Originally Posted by mstell2

What are you trying to achieve with this modification?


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X2

[Herk7769]

Originally Posted by mstell2

What are you trying to achieve with this modification?


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Sorry I have been a bit busy and have not had time to answer.

Someone on the forum a while ago was up on the roof of his RV working on the air conditioner and noticed the air handler was ice cold. He thought that meant he was losing cold air through the cracks and crevasses of the loosely screwed together air handler. His solution was to metal tape all the corners to seal the unit air handler and then he glued Mylar insulation to all the flat surfaces to keep the cold air in and the hot air out. I agree and his (and my) mod allowed my unit to function flawlessly in the Texas 115 plus heat.


As to insulating the large compressor pipe:

"The large, cold, low pressure line, carrying the evaporated refrigerant from the air handler, should be insulated to prevent condensation. The small, warm, high pressure line, carrying condensed refrigerant into the air handler, should not be insulated. I am not an air conditioning professional so your mileage may vary.

Explanation: The unit outside the house compresses the refrigerant from the large line. This makes the refrigerant very hot. Then the refrigerant is run through the condenser coils and the fan blows outside air over them to remove the heat and condense the refrigerant back to liquid. The small line now carries the warm liquid refrigerant back into the house. No insulation is needed on this line because it is still warmer than the outside air. If the air cools it some more, that only helps. In the house, the pressurized liquid refrigerant is allowed to rapidly decompress in the evaporator coil. The instant drop in pressure causes an instant drop in temperature, making the evaporator coil very cold. Interior air is blown over this coil, cooling the air and warming the coil and refrigerant. The evaporated refrigerant, which is still rather cold, now flows out of the house in the large pipe. It does not help us for this refrigerant to get warmer after it leaves the evaporator coils. It just makes it harder to compress and cool in the condenser coils. So we want to prevent condensation on this pipe. That is the reason for the insulation. "

[Justice]

Last week managed to do this mod on our Coleman Mach AC 15k. This week we're in Kansas and outside temps are in 90's and expected to see 100s. The mod has improved the performance of the unit. Thanks Herk7769 on

[Soga65]

Also did this mod after reading this an was very pleased with the out come camping in Fla last wkend, I have a tan roof an now debating coating it white , Trying everything before installing a second Ac .

[Paul GA]

Did this morning... finished and it was 82 inside. Cranked her up and two hours later dropped 7 degrees to 75.

Never could get below 80 in full sun before.

[BDavis]

Our Dometic AC units have black cowlings. Would painting them white really make that much of a difference?

[Herk7769]

Originally Posted by BDavis

Our Dometic AC units have black cowlings. Would painting them white really make that much of a difference?

IMO, no. Keeping the cold air INSIDE the camper is more important as it has a greater effect on cooling the inside. Making the ROOF white reflects heat that would have been absorbed by the camper back into the atmosphere. The cowling's impact on the heat inside the air conditioner (exclusive of the air handler) should be minimal. The giant fan blowing across the compressor coils is using ambient air at outside air temp anyway.

[Jimandchris]

Herk, do you happen to remember what size the refrigerant line is that needs to be insulated? Great looking mod and I have plenty of reflectix left over for evaporator box - may as well do it all at once.
Thanks!

[rockfordroo]

Originally Posted by BDavis

Our Dometic AC units have black cowlings. Would painting them white really make that much of a difference?

Actually, black on the back half (condenser) may actually be better. As I learned in engineering school, a "true black body" will absorb all incoming heat if colder, but will give off heat if warmer. So black will dissipate the internal heat better than white, while white reflects external heat better than black.

So, in theory, better to have white on the evaporator cover and black on the condenser cover. But it would take some experimentation to prove it.

And the amount of "improvement" is probably not even worth worrying about.

[aceinspp]

Originally Posted by rockfordroo

Actually, black on the back half (condenser) may actually be better. As I learned in engineering school, a "true black body" will absorb all incoming heat if colder, but will give off heat if warmer. So black will dissipate the internal heat better than white, while white reflects external heat better than black.

So, in theory, better to have white on the evaporator cover and black on the condenser cover. But it would take some experimentation to prove it.

And the amount of "improvement" is probably not even worth worrying about.

This one reason why motor vehicle engines are painted black. Later RJD

[Herk7769]

Originally Posted by Jimandchris

Herk, do you happen to remember what size the refrigerant line is that needs to be insulated? Great looking mod and I have plenty of reflectix left over for evaporator box - may as well do it all at once.
Thanks!

The large diameter pipe is cold when running and that is the one you insulate. The small one is hot when running so you should not insulate it. I do not see any need to insulate the hot section as you want THAT heat to leave the enclosure.

[jeff64]

Anyone have experience doing this mod with something other than reflectix? The bubble wrap material seems a little flimsy to me and the R values, from what I've read are more like R-1 than R-5. The overall concept here seems to be a winner. Would like a more robust material with a better or at least consistent R- value. I'm leaning to Frost-King Aluminized duct wrap, self adhesive, R-3 on the air handler housing. The cost is comparable

[MarkyB]

I've done similar mods to my Jeep.
Insulated the cold pipe in the engine bay, and lined the inside of tub with the reflectix. The insulated pipe makes the a/c blow just a little bit cooler... The reflectix under the carpet helps with heat transfer through the floorboards. It's about changing the percentages in your favor just a little bit. Even if it's "1%", the result is the Jeep is nice and cool even with a soft top 95 degree weather.


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[Herk7769]

Originally Posted by Jimandchris

Herk, do you happen to remember what size the refrigerant line is that needs to be insulated? Great looking mod and I have plenty of reflectix left over for evaporator box - may as well do it all at once.
Thanks!

Not 100% sure but I think I used 1/2 inch pipe foam insulation I had around the house.

[Paul GA]

1/2"

[Captain America]

1/2" is what I used

[Fire Instructor]

There's a parallel thread to this running over on the Jayco owner's forum, where I now spend most of my 5'er forum time..... It was mentioned that the tread, and the idea originated on the Forest River Forum, and I said to myself that it looks like the kind of thing that Herk would try.... So, I looked for it today, and lo and behold! Herk's the guy who started it! LOL!!!

Disregard the info in the sig. Traded the Rockwood for a North Point (Jayco) 377RLBH late last Fall. Took all of the solar stuff off the Rockwood and reinstalled it on the 377!

[SeaDog]

It a good move to insulate the suction line (cold as you call it) it will help the AC run a little more efficiently. I have done this to mine and added a hard start. I plan to do the reflex soon. good job