Roof A/C

[JohnSiebert]

Trouble with cooling a 2015 Holiday Rambler Vacationer 36SB Class A with two 13,500 AC. Has any one had this problem? To reduce heat build up from the sun, I have painted the AC cover, from black to white. Cleaned the coils and straighten out any bent fins. Painted the dark color trim around the top edge of the roof. Added a larger cooling fan to the back of the refrigerator to pull the heat from the unit. This has help a hole lot but still not cooling the inside on a sunny day.
I am thinking of removing the front room 13,500 AC and replacing it with a 15,000, or installing a third 13,500 AC, but a third AC would put a larger amp load on the 50amp connection.
The question is, has anyone added a larger AC or added a third AC to there RV, and did it fix the cooling problem?
John Siebert

[Old-Biscuit]

Have you measured air temp differences?


Return air vs discharge air temps>........hopefully 18*F-20*F difference


IF NOT....then warm return air is mixing with cool discharge air/plenum--return area not sealed for each other.

[tombottcat]

we have found that in the arizona summer when we use two sets of blinds on all windows has made a huge difference and along with leaving the settings on Auto, a tech told me these units don't preform well on high cool, go figure,hope this helps, YOU CANT GET LOST IF YOU DONT CARE WERE YOUR GOING

[Lt Dan]

Before you go to the expense of adding or modifying the A/Cs, get a set of exterior sun screens. If you can stop the sun from getting inside the windows you can reduce the heat load by a large percentage. MagneShade and SunProMfg are two great sources for screens

[Quincy]

Lt. Dan is right.

Even if you have lived a life of celibacy you cannot expect any more than about eighteen degrees drop in temp from outside to inside. If you are in Phoenix in the summer time (and I don't see why anyone would be) you wont get the inside temp comfortable during the hottest part of the day.

You don't say where you want the temp to be inside the rig. If you expect 70 degrees then it cant be any hotter than a max of 90- out. That is if everything is working perfectly.

[jerichorick]

Originally Posted by JohnSiebert

Trouble with cooling a 2015 Holiday Rambler Vacationer 36SB Class A with two 13,500 AC. Has any one had this problem? To reduce heat build up from the sun, I have painted the AC cover, from black to white. Cleaned the coils and straighten out any bent fins. Painted the dark color trim around the top edge of the roof. Added a larger cooling fan to the back of the refrigerator to pull the heat from the unit. This has help a hole lot but still not cooling the inside on a sunny day.
I am thinking of removing the front room 13,500 AC and replacing it with a 15,000, or installing a third 13,500 AC, but a third AC would put a larger amp load on the 50amp connection.
The question is, has anyone added a larger AC or added a third AC to there RV, and did it fix the cooling problem?
John Siebert

John, may folks, previous to this post, have expressed some very valid points. My add to this may not help much but here it goes.
Starting to cool the coach off before you start to feel the heat of the day is most important. As someone has stated, keep the shads down, especially in the drivers area.


Upgrading to 15K units is not a bad idea and could help. Adding a third unit is another option. I have 3 units on my coach and the 50A service handles them fine. You generator would be the thing to be considered. I have to shut off one A/C breaker when on generator. The 8KW generator won't handle the loads.


Hope you can find a way to stay cool.



Happy trails.

[vito.a]

I just upgraded one of our AC units to a 15k. This new AC is working really well and cools down the interior much faster. http://www.irv2.com/forums/f115/repl...ch-405503.html

I also made an insulated inside windshield cover out of Reflectix. Most of the inside heat on these coaches comes from the windshield.
https://www.lowes.com/pd/Reflectix-1...5-ft-L/3011906

[bruceisla]

Depends on where you are located. I had 2 - 13.5k Dometic units in our much older Endeavor. I made some changes that made a difference. Reflectix in the windshield, awnings extended, automobile sunscreens in as many windows as possible, keep all the shades down, park in the shade when possible. Satisfactory in high 90's.


The biggest single change was Reflectix in the windshield ... resulted in a 7 degree drop in/beyond the cockpit.

[Old-Biscuit]

Originally Posted by Quincy

Lt. Dan is right.

Even if you have lived a life of celibacy you cannot expect any more than about eighteen degrees drop in temp from outside to inside. If you are in Phoenix in the summer time (and I don't see why anyone would be) you wont get the inside temp comfortable during the hottest part of the day.

You don't say where you want the temp to be inside the rig. If you expect 70 degrees then it cant be any hotter than a max of 90- out. That is if everything is working perfectly.

'


That 18*F drop is between the A/C return air and the A/C discharge air temps


Outside air temp DOES impact 'heat load' but even if 100's outside you CAN cool inside down to 70*F


Heat load is amount of heat coming in via windows/roof vents....block that and lower the heat load.

[MSHappyCampers]

Hi John! Welcome to IRV2! We're sure glad you joined the gang!

Changing the front A/C to 15K would help, but probably not as much as you might think. I would concentrate on blocking the heat, including window tinting, reflective roof coating, more efficient shades, etc.

Good luck, happy trails, and God bless!

[vito.a]

The 18 degree temperature differential is not accurate on our new AC. The cold air blowing out of the vents is 47 degrees with a higher volume. Our older AC output air is 55 degrees.
Outside air temp was just over 100. Inside started at 95 and pulled down to 75 in less than an hour.

I can tell you that this new Penguin II 15k heat pump much works better than the older units.

[AE Wanderer]

We bought a role of reflectix at Home Depot. Cut it to fit the inside of the windows. Made a huge difference. Especially in the cab/front. We saw a 24-26 degree drop from outside temp to inside temp.

[bruceisla]

Originally Posted by vito.a

The 18 degree temperature differential is not accurate on our new AC. The cold air blowing out of the vents is 47 degrees with a higher volume. Our older AC output air is 55 degrees.
Outside air temp was just over 100. Inside started at 95 and pulled down to 75 in less than an hour.

I can tell you that this new Penguin II 15k heat pump much works better than the older units.

The 18 degree number is on the low side. The spec has variations depending on outside air temp and humidity. A typical number is 20 - 23 degree Delta. Your observation is likely to be typical of the new Dometic units which have much better "under the shroud" insulation. The Brisk II unit has something similar to dense styrofoam ... I assume the Penguin II is the same. My old Penguin/DuoTherm had sheetmetal and thin fiberglass batting.

[BUB1988]

As others mentioned adding the reflectix from Home Depot for the windshield. We also cut out and put on the back wall of all of the cabinets. Worked well in lowering the heat in the cabinets.