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Old 08-10-2015, 10:41 PM   #15
"Formerly Diplomat Don"
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I think you have to look at this two ways. First, if you're parked, it cools down substantially at and night and you have everything closed, 2 units in a 40 unit will be just okay.

The second situation where you've been driving all day and it doesn't cool down at night, for example....Vegas, 2 units won't cool the coach down past about 79-80 degrees.

It also depends on what you think is cool. For me, cool is about 72-73 degrees. My new Dutch Star, with two 15K units won't get anywhere near that on a 100+ degree day. I wish I could add a third A/C, but there just aren't that many times where we camp in that type of heat to justify adding another. If I were to order a new coach, I would definitely order a third unit.

Don & Mary
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Old 08-11-2015, 05:50 AM   #16
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Has anybody installed a roof A/C unit (or replaced one)? What am I missing here?

After locating a spot inside and outside, slice the roof and remove top piece in order to look for trouble between roof and ceiling panel.
If none found, find electric wire that powers one of the roof A/C units (shouldn't it be running on centerline down length of coach?)
Finish cutting into coach.
Horse new unit into place after splicing the A/C supply wire and pushing aside.
Connect wire, install trim, caulk roof

A/C would work in tandem with the other unit's thermostat.

Is it that easy?

Rick and Sandy
2003 American Eagle, 52K miles
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Old 08-11-2015, 07:06 AM   #17
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I have friends with a 37' coach that has 2 15k units and in the extreme heat (105+) it does not keep up without floor fans. Their coach has 4 slides and it is just too much for those 2 units, it should have 3 for the south in summer.
Kent - '03 Fleetwood Storm Ford F-53 V-10
With Susie (Lhasa); Angie (Shorkie) Ferbie (ShihTzu)
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Old 08-11-2015, 07:44 AM   #18
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I think Smitty hit most of the points earlier and Don the most important one... to those that say two is enough - bet if you came to the south you'd sing a different tune
(Hate to quote the NYT, but here is an interesting take on population shifts)

Yesterday I was out in the rv while a tech was working on it and it was 108 inside!
I was melting (since after quitting sports LONG ago I have been an 'office jock'!) but the tech was barely sweating... he's acclimated to the heat, like I USED to be

So, in MY case, four would not be enough
'11 Monaco Diplomat 43DFT RR10R pushed by a '14 Jeep Wrangler JKU. History.. 5'ers: 13 Redwood 38gk, 11 MVP Destiny, Open Range TT, popups, vans, tents...
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Old 08-12-2015, 01:08 PM   #19
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Another consideration is which brand of MH you are looking at. From my limited experience, the Newmar and Entegra are better insulated and will cool down better that most other brands. I know for a fact that my sons 45' Mountain Aire cools better than our 44' Allegro Bus. Many companies use the same construction methads as Tiffin, so they would be similar to ours. If the front cap above the windshield is not insulated well, a lot of heat will come through that area. A good way to check is on a hot sunny day after the coach is cooled down, open a cabinet up near the ceiling and feel how warm it is. This will tell you where a lot of heat can be coming through. FWIW, most brands 40' or longer, will need three A/C units to cool a 40' coach down to 72* sitting in 95* sunshine. A 40' Newmar or Entegra would be fine with two.
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Old 08-12-2015, 01:19 PM   #20
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Originally Posted by Lincolnboy2 View Post
I have friends with a 37' coach that has 2 15k units and in the extreme heat (105+) it does not keep up without floor fans. Their coach has 4 slides and it is just too much for those 2 units, it should have 3 for the south in summer.
Some brands are better insulated than others. So far our Magna seems to be as well insulated as the previous Dutch Star. I wish all manufacturers would publish the insulation factors for their rigs, but most don't want to let you see how little insulation there is.

2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
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RV'ing since 1957, NRA Benefactor Life, towing '14 CR-V
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