Two AC's...

[aknavy]

Will two AC's keep a 42 foot Newmar cool in Florida/Texas summer? If not, what would it take to add an AC?

[LJowdy]

A lot depends on how well you insulate the front windshield and side windows the BTU's put out by the A/C units and just how cool you want it to be.

Typically a 42' would or should have 3 A/C's and trying to install another is a major undertaking. The first thing to do is call Newmar and find out if it's wired for a 3rd unit. Once you know that then you can either proceed or spend a lot of time trying to figure out how you're going to do your wire runs and, getting a wire back to a thermostat. If it is wired but no provisions for a thermostat then you could install a manual controlled A/C, in other words, you turn it on and off via a switch on the vent plate.

[wildtoad]

I’d say that the two states you mention might be a bit shy on natural shade so you’ll have full sun a lot of the time and you two units will not meet your expectations. Are looking at buying a used unit or buying new? If new, order it with three.

[aknavy]

Originally Posted by wildtoad

I’d say that the two states you mention might be a bit shy on natural shade so you’ll have full sun a lot of the time and you two units will not meet your expectations. Are looking at buying a used unit or buying new? If new, order it with three.

This is a used unit that has two AC's installed. Would prefer to have a third, but it doesn't.


Was hoping that the feedback would be positive, as my 39 foot fiver with two AC's stays cool.

[Capt. Bill]

Definitely get 3 - I have a 43' MADP & it struggles in FL when it's 93 + out in the sun.

Happy Trails

[JC2]

What we have done/do in situations where existing ac,(s) might be borderline in efficiency is to turn both ac fans to manual on either to low or high. Next set the thermostat to 72-73 which will allow the compressor(s) to kick on/off but let the fans continually run. Keeps air inside circulating continually. At night u can set the fans back to auto if temps get cool enough the turn back to manual if needed the needed.

[96 Wideglide]

Originally Posted by aknavy

Was hoping that the feedback would be positive, as my 39 foot fiver with two AC's stays cool.

Doesn't have a massive windshield.

An outside mounted windshield cover would be a good investment. Also start cooling coach in the morning. It's easier to keep it cooled, than trying to cool a 80* coach.

[Sky_Boss]

Having had one before...

It will be a challenge to keep things comfortable but not impossible. What year and model are you looking at?

A few thoughts are:

1. Use windshield covers on the OUTSIDE (like Magneshades) to make a MAJOR improvement.

2. I also had outside covers on all cockpit windows and larger windows in the living room area.

3. Use window awnings as much as possible.

4. Use your patio awning as much as possible. This can be especially helpful when it can shade one side during the extremes of the sun exposure. BTW...since older Newmar's to have topper awnings over what is typically the kitchen slide we also rolled the awing out enough to cover that slide. It made a big difference in keeping the slide cabinets on that side cooler.

5. Lock fans on high during the day.

As to adding a 3rd AC you could consider adding it outside of the current power distribution system. Installing a separate breaker box in the power bay would allow you to use a separate 30 amp circuit with its own plug. You could then use what it typically an extra, unused 20 or 30 amp pedestal outlet to power it. I'm no expert on how you would install the HVAC itself but it would be a way to get a 3rd AC in without causing other issues trying to integrate it with current power distribution.

[aknavy]

Originally Posted by 96 Wideglide

Doesn't have a massive windshield.

Didn't consider that.

[aknavy]

Originally Posted by Sky_Boss

Having had one before...

It will be a challenge to keep things comfortable but not impossible. What year and model are you looking at?

2005 Mountain Air 4304.

[bruceisla]

We have a 45' and frequently run all 3 units when outside temp hits 95 and the RV has lots of exposure (long summer days).


Call Newmar and ask if the roof on your RV has the framework installed for a 3rd A/C. This is far more important than the wiring. If the framework is there you can pull additional 12vdc and the Dometic communication cable wiring from the "middle" unit .... can be pulled thru the existing ductwork. A remote sensor can be added to #3 and fastened inside a bedroom return vent ... it's not necessary to mount on wall. A degree or 2 of accuracy is not important (the wall mount sensors aren't that accurate anyway).
Ask whether the 120vac wiring is in the roof near #3.

The other item is generator capacity ... do you have a 10K/12.5K genset?

[96 Wideglide]

Wow! M.A with only 2 A/C's

[twojayhawks]

If the 2005 MA is as well insulated as my 2015 DS I believe you can be comfortable with two 15K AC units.

[Dutch Star Don]

I know that Newmar does a good job with insulation, but two A/C's are not enough in their 40' models. Some say they get theirs cool in Arizona in 105 weather, but their idea of cool is not mine.

We've had two identical 40' Dutch Stars and in 105 degree weather, the units will barely keep the coach at 80 degrees. If you arrive in the afternoon and start them, you won't cool down until the early morning hours.

In a PERFECT situation, where the sun is shining just the right direction, you have a tree, you black out everything in the coach and start the A/C's at 7:00 am, you might keep it comfortable.

We keep a medium sized box fan in the coach, partially close the bedroom door and pull cool air from the bedroom, forcing it into the main cabin area. This will keep it livable if you don't move around.

My idea of cool is 74-75 degrees.