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Old 01-16-2025, 04:48 PM   #1
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Class A Roof AC units?

Hello - I am considering buying a new or recent Newmar 45' Class A Motorhome (King Aire, Essex, London Aire) - and noticed that nearly all of the 3-AC Units are 15 ton each with heat pumps. Appears that all manufactures use the same.

As I understand most of the Prevost converters have 4-AC units with 15 ton each with heat pumps versus 3 for Newmar and other manufactures?

We live in Texas and travel to Florida in the winter and Midwest/North in the summer, so we need good AC most of the year.

Would we be happy with 3 units on the roof in a warm climate, or should we rethink our plans for 4 units?

Also, Newmar and others including Prevost are installing large inverters and Lithium Batteries to power 1- 2 AC's for traveling, plus Prevost and some specialty shops offer an alternator package as well on the engine. Would like to hear your thoughts on tis any and pros/cons to consider.

Many thanks,
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Old 01-17-2025, 11:52 AM   #2
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We have two in our 36 and wish for three.

So, my rule of thumb is one A/C per 12 feet is comfy. So, yes, go for four if budget is less of an issue than living in a 78°+ coach in summer.
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Old 01-17-2025, 01:14 PM   #3
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Thanks for your feedback!
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Old 01-17-2025, 01:25 PM   #4
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If you have the 4 option available on a higher end coach, I reckon that would be nice.

However, we have 3 and have never wished for 4. It’s all about managing your coach.

Also, I would imagine that 4 may not be adequate in certain circumstances either. Just have to keep them running at peak performance.
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Old 01-17-2025, 01:31 PM   #5
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Apollo2, just a quick bit of information for your reference, Your units are 15,000BTU which equal about 1 1/4 ton. Having 3 of them is fantastic. Having camped in Las Vegas during the summer at 116° during the day, my two units barely kept up so 3 will be perfect!

Safe Travels!
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Old 01-17-2025, 02:00 PM   #6
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Apollo2, just a quick bit of information for your reference, Your units are 15,000BTU which equal about 1 1/4 ton. Having 3 of them is fantastic. Having camped in Las Vegas during the summer at 116° during the day, my two units barely kept up so 3 will be perfect!

Safe Travels!
That is not camping.

I am in Las Vegas at the moment. I rarely run my A/C. My RV has wheels and goes where A/C is not needed.

I am on a 20 amp service. When I had to be here in the summer, I closed off the back and just ran the bedroom A/C. It was fine for sleeping.
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Old 01-17-2025, 02:05 PM   #7
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I cant argue with that! We were on our way to Utah for a family wedding and this was just a layover stop fortunately! And with 4 Aussie's on the trip with us

Safe Travels!
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Old 01-17-2025, 02:22 PM   #8
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Originally Posted by Apollo2 View Post
....

Also, Newmar and others including Prevost are installing large inverters and Lithium Batteries to power 1- 2 AC's for traveling, plus Prevost and some specialty shops offer an alternator package as well on the engine. Would like to hear your thoughts on tis any and pros/cons to consider.

Many thanks,
Welcome to the forum.

It is not practical to run A/C on batteries. It's an engineering thing. A/C needs Detroit muscle.

If I need A/C when driving I run the roof A/C on the generator. You need to load up a generator for at least an hour a month.

I am old school. I do not have any experience with systems that run motors in with inverter technology. In a house, it is nice to have the fan ramp up to speed. Running off the alternator may reduce how long it lasts.
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Old 01-17-2025, 02:33 PM   #9
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"Also, Newmar and others including Prevost are installing large inverters and Lithium Batteries to power 1- 2 AC's for traveling, plus Prevost and some specialty shops offer an alternator package as well on the engine. Would like to hear your thoughts on tis any and pros/cons to consider"

I wondered when this technology would finally show up! If I had the option to have that system on my RV I would do it in a heartbeat! The flexibility is incredible allowing you to run everything that is 110/120 in dry camping spots. Its definitely something you should consider at the very least!
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Old 01-17-2025, 02:36 PM   #10
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Hello - I am considering buying a new or recent Newmar 45' Class A Motorhome (King Aire, Essex, London Aire) - and noticed that nearly all of the 3-AC Units are 15 ton each with heat pumps. Appears that all manufactures use the same.

As I understand most of the Prevost converters have 4-AC units with 15 ton each with heat pumps versus 3 for Newmar and other manufactures?

We live in Texas and travel to Florida in the winter and Midwest/North in the summer, so we need good AC most of the year.

Would we be happy with 3 units on the roof in a warm climate, or should we rethink our plans for 4 units?

Also, Newmar and others including Prevost are installing large inverters and Lithium Batteries to power 1- 2 AC's for traveling, plus Prevost and some specialty shops offer an alternator package as well on the engine. Would like to hear your thoughts on tis any and pros/cons to consider.

Many thanks,
Cover your roof in stand off solar panels and install Airflow mod in living room. One Ac cools my rig 38ft rig on the hottest days and don't have to listen to bedroom ac all night!
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Old 01-17-2025, 02:45 PM   #11
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Quote:
Originally Posted by Apollo2 View Post
Hello - I am considering buying a new or recent Newmar 45' Class A Motorhome (King Aire, Essex, London Aire) - and noticed that nearly all of the 3-AC Units are 15 ton each with heat pumps. Appears that all manufactures use the same.

As I understand most of the Prevost converters have 4-AC units with 15 ton each with heat pumps versus 3 for Newmar and other manufactures?

We live in Texas and travel to Florida in the winter and Midwest/North in the summer, so we need good AC most of the year.

Would we be happy with 3 units on the roof in a warm climate, or should we rethink our plans for 4 units?

Also, Newmar and others including Prevost are installing large inverters and Lithium Batteries to power 1- 2 AC's for traveling, plus Prevost and some specialty shops offer an alternator package as well on the engine. Would like to hear your thoughts on tis any and pros/cons to consider.

Many thanks,
Prevost and Newell cater to a completely different use and mindset clientele. The focus for many of these coaches is entertainment. It has been said the ultimate coach sleeps, 2, diner for 4, and cocktails for 6. Heat and AC is sized to tolerate the doors being left open and traffic in-out during the day. On board power is designed to accommodate long term travel, (touring) whereas most RVs are designed for us at the destination. In addition to the difference in build the high-end stuff will get 20kw generators, multiple engine alternates, and either over the road heat and air or enough power off the engine to feed all the ACs. Even foe heat and hot water you see the Aqua Hots, sometimes more than one and multiple 10-gallon water heaters. For plug in power, you will see 80 amp or multiple 50-amp connections. 24 volt, 500 amp engine alternators ,(12KW) are common.

That said 3, 15,000 will do a nice job keeping a 45-footer with slides cool. That is 45,000 BTU of cooling. Compare that to having a 45,000 Btu boiler trying to raise the temp of the rig from 20 to 70 degrees. Except for the sun load that is plenty of cooling to drop interior temp 20 to 30 degrees.
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Old 01-17-2025, 03:23 PM   #12
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If you have the option to go for 4, then by all means get 4. Three may be enough unless you spend the summer in Moab.

Something that is important to us is redundancy. If one goes out, I don't want to have to interrupt the trip because we are uncomfortable in the coach. My wife does not like to be hot. Happy wife, happy life.

There is a reason entertainer coaches usually have 5 roof airs.
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Old 01-17-2025, 04:21 PM   #13
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My neighbor helped trade out 4 AC's on a large Super C that is normally used at the race track. The owner said the original AC's would keep up but barely. The newer AC's use a different refrigerant and are much more efficient. Owner says he can now get by with 2 AC's.
So do some checking on what AC's are being used and see if they are the new improved type.




I changed out both my older 13.5K BTU Duotherms and replaced with new 15K BTU Penguins. The old ones struggled to keep up in hot weather. Now if temps are 95F I can run one AC unit.
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Old 01-17-2025, 04:38 PM   #14
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Originally Posted by jacwjames View Post
My neighbor helped trade out 4 AC's on a large Super C that is normally used at the race track. The owner said the original AC's would keep up but barely. The newer AC's use a different refrigerant and are much more efficient. Owner says he can now get by with 2 AC's.
So do some checking on what AC's are being used and see if they are the new improved type.




I changed out both my older 13.5K BTU Duotherms and replaced with new 15K BTU Penguins. The old ones struggled to keep up in hot weather. Now if temps are 95F I can run one AC unit.
I think this post needs to be highlighted. My father-in-law has worked in HVAC for years and understands this stuff. Says the new units and refrigerant are a lot more efficient. So the answer more is “depends” than anything. Meaning which model AC/heat pump are being used. What type of insulation is being used, double pane windows etc.

We have a three unit 15000btu setup and have spent the hottest of the hot and humid summer in Houston. It handled it fine and was extremely comfortable. We also have automatic window awnings we use and an exterior mounted windshield shade. Those things matter.
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