A/C Expectations

[CJ7365]

40' RV = at least 2 15,000 BTUs

[triplewide]

Originally Posted by W5WTX

Need to calibrate my expectations. We spent this past weekend at Lake Mineral Wells State Park near Mineral Wells, TX. Very nice park and I recommend it. That said, we picked one of the hottest weekends of the year to go. Heat of the Day temperatures where in the 106-108F range.

We have a 2003 American Eagle with one 11.5K and one 13.5K BTU AC units. With both running full on, the interior coach temperatures rose to the mid to high 80s during the hot afternoons. I would have expected better cooling but I really have nothing to compare to since this was our first trip during a really hot spell. I put a thermal gun on the discharge air of both AC units. discharge air was consistent on both units at about 65F.

What should my expectations be for cooling and maintaining coach temperature on extreme hot days?


Doug
Amarillo, TX

You currently have a total of 25K BTU. If you upgrade to two 15K units for a 30K total and a 20% improvement.
If it were me I would look into adding a third unit at 15K. This would give you a total of 40K for a 60% increase. If the two current units are working properly, as it sounds, then replacing them is a large expense for a small gain.


The third unit could be added at an existing fan opening if you have one. It may not be supported by your generator, depending on its size. It need not be ducted, straight dump would serve your purpose. Would cost about the same or less and would add redundancy to your your AC units.


I added an AC to an ACE 29.3 with similar issue as yours, solved my problem.

[Tha_Rooster]

OP’s question is not cut and dry. Location,temp,how long the sun hits without shade, do you have a windshield sun screen etc.... A very general rule of thumb is 20 degrees or so cooler than the outside.

[tommar]

FWIW, once the sun goes down, the temps in my MH rapidly go down. By the time it's bedtime, I actually have to turn the thermostat up because it's too cold to sleep! Honest! Then, the next day, insidiously, the temps creep up. But the tower fan keeps it tolerable. Would not want to go to AZ or Death Valley! Texas is bad enough!

[maf92]

We are in SC, and installed two new units on our motor home two years ago. Upgraded the main unit to 15btu from 13.5. Still 13.5 unit in the bedroom. We installed thermal/darkening fabric to the backside or our windshield curtains, and use reflective rolled stuff in the other windows if needed. No problem keeping the unit at 69 degrees ih heat of day. We camped in Columbia at the fairgrounds for USC football game and it stayed cool with absolutely no shade at all.

[JMonroe]

I suspect you've got the gist by now. Too little BTU for the size coach. An inexpensive desk fan can fit almost anywhere and will help a lot with personal comfort. When the old one(s) die, well, you know what to do.

[AE Wanderer]

X2 on the Reflextix. We had our 2008 AE at China Lake, California. We could not keep inside temp under 80°F in the afternoon. It was 112°F outside. Bought a roll of Reflectix, cut to size for each window, and inside temps lowered 12°F! Also, you can make a curtain to go just behind the cab portion. Those big windows up front let alot of heat in. Park your rig facing east so you don't get the afternoon sun on those huge windows.

Agreed that you need 15K air conditioners. My coach is 42' long and has 3 ACs on it. All are 15k.

[backpack96]

When we purchased the used coach we installed Reflectix in the closet, which had a very large wall, and in each cabinet throughout the MH. Not sure if it really helps but figured that it would not hurt. I used Reflectix for the windshield but after reading the positive comments on the Magna Shade I placed an order for one yesterday. Would like to thank all of the more experienced people who take the time to review the posts and who provide some very valuable information. I am amazed at how technical some of the posts are and how people go out of their way to help others.

[W5WTX]

Yep, I got the message. Too much heat, not enough insulation and too few BTUs/hr. My American Eagle has been in Texas since it was new. I’m the second owner. I suspect in its day and time, the AC units I have were the base equipment offered by American Coach.

I will try some of the low dollar suggestions first. If we don’t feel like we can live with the results, I’ll explore beefing up what I have or as was suggested, adding a third unit. Swapping out to larger units although pricey, would be easy as long as my 20A / unit wiring is enough. I’ll look at some specs and see.

So again, thanks to all who shared their thoughts. This is why I like this forum.

Regard,
Doug
Amarillo, TX

[Roadmiester]

Your 20 amp wiring for the A/C's will be fine for 15k btu. We have 3 15k btu's and each one is on a 20 amp circuit. They will pull around 14 amps when running. What you have to watch is other things on at the same time. For example, to run our dryer we need to shut off A/C #3 and the same thing if we use the microwave. The parks 50 amp services will sometimes handle all the load, but not all the time. You will need a 10k generator to run 3 15k A/C units. Have you done anything about your roof? I have a fiberglass roof and put two coats of Dicor on it to reflect heat. And like many have said, the heat coming in from the front is the killer. Keep the sun off that big windshield. That said, we have no problem keeping 70 degrees inside from Florida, Texas and California.

[TXiceman]

Originally Posted by Tha_Rooster

A very general rule of thumb is 20 degrees or so cooler than the outside.

This is WRONG. The internet keep propagating this incorrect information.

The 20 degF temperature difference if the A/C unit inlet ait temperature to the A/C outlet temperature.

Ken

[W5WTX]

Originally Posted by TXiceman

This is WRONG. The internet keep propagating this incorrect information.

The 20 degF temperature difference if the A/C unit inlet ait temperature to the A/C outlet temperature.

Ken

Understood. What you said about temperature Delta was clear from the start. Thanks TX Iceman.

73,
Doug

[tuffr2]

Agree that you is going to be normal. Especially with two small(ish) A/C units. 11,500btu is not used except on the smallest of units anymore.

Not sure but you could look into replacing the 11,500 btu A/C unit with a new modern 15,000 btu unit. That will help a bit, my guess is 2 or 3 degrees cooler.

I know it is miserable as I spent a summer in stinkin hot and muggy Virgina on just a 30 amp electrical service in my 5th wheel. I was in direct sunlight 94 degrees. Lucky I could keep the bedroom cool. But it was miserable. Oh, I had 2 15,000btu A/C units but could only run 1 A/C unit at a time.

[stew1]

Best thing we did for the heat was a windshield cover that’s on the outside, made a big difference in cooling and window awning