Air Conditioning Question

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
P

Pilothawk

Active member
Joined
Apr 21, 2018
Posts
30
There are two class C coaches in the area I have viewed.  Both are 31 footers....one Winnie and a Jayco.

My question is the number of A/C units on a coach of that size.  Each of these has only one A/C.  Even though ducted...is this enough cooling for that large a coach? 

My current TT has two A/C units , one ducted, and it is not cold in the heat of summer in the Mid-south.
 
Pilothawk said:
There are two class C coaches in the area I have viewed.  Both are 31 footers....one Winnie and a Jayco.

My question is the number of A/C units on a coach of that size.  Each of these has only one A/C.  Even though ducted...is this enough cooling for that large a coach? 

My current TT has two A/C units , one ducted, and it is not cold in the heat of summer in the Mid-south.
Click to expand...
I think you answered your question already. 

Check to see if the A/C is 13,500 BTU or 15,000 BTU.  Obviously the larger one will do better, but in 90+ temps two A/C will do better than one.
 
A 31 foot class C is a bit more centralized than a similar length trael trailer (the cab uses a fair amount of space), so it tends to be somewhat ok with the a/c in the center. A trailer that size needs an a/c in each end.  That said, I would want two a/c if possible.
 
I am old now.  I don?t sleep well if it is hot and muggy. 

Here in the mid-south, humidity can be unbearable.  Spent a week last August at a 30 amp site.  The weather was hot, the humidity oppressive.  I could only run the one A/C unit.  Nights were OK...days not so much.
 
Shade makes a lot of difference. My 30' Class C has one 13,500 Dometic not ducted. Non ducted creates much more air flow which keeps you cooler like a ceiling fan. Mine isn't a good comparison if compared to a ducted system but I would expect even a 15K ducted AC would be marginal over 90.

In in MS on a 95 degree day with 90% humidity if the lot is in full sun then the compressor will run non stop and pull it down to 77. Which is still ok because of the air movement. At 90 degrees in full sun or 95 on a shady lot it pulls it down to 70. It does help if you close the curtains on the overhead bunk and put the cover over the windshield since they are hot spots.
 
In my not very humble opinion one A/c is not going to cut it on anything over 30 feet. 20 feet pernaps 30 feet no way and as the world warms even on a 20 you might want MORE
 
Most folks don't understand that normal cooling with A/Cs won't do better than about 20 degrees cooler than outdoors.>>>Dan
 
Those big windshields allow a lot of heat to enter the motorhome so the more A/C the better, whether it's more units or larger units.  Also a light-colored solar screen helps reflect sun away from the windshield when you're parked.  Awnings can help shade the windows.  We also use foam vent inserts and I made blackout curtains for the bedroom.  Those help keep the cooled air inside in the summer and heat in during cold weather.  Finally, a lighter color exterior helps reflect the sun's rays from the entire motorhome.  You might not want the expense of painting it a lighter color but it's something to keep in mind when you buy your next one.  We have a 3-shades of blue exterior and the original graphic had the darkest blue on top.  We asked them (factory order) to put the lightest shade on top and are quite pleased with the result.

ArdraF
 
In my area the temperature has been in the high 90's with 90% humidity. The a/c will cool and lower the humidity. In my TT, I also use a small a dehumidifier which seems to make a big difference. In fact, it can get darn cold in here. But, my TT is also in a wooded area in shade all day except for the mornings which probably makes the biggest difference in being able to keep it cool all day.
 
Utclmjmpr said:
Most folks don't understand that normal cooling with A/Cs won't do better than about 20 degrees cooler than outdoors.>>>Dan
Click to expand...
Isn't that suppose to be cooler than the inside air temp?

Also it makes a big difference on what color the outside of your vehicle is.
 
In some rigs you want 3 of them. In our fiver (42 footer) it came with 2, but during these 98 to 105 degree temps the 2 don't quite keep up. I finally went to Lowe's and bought a portable 10,000 btu unit, the kind that has an exhaust tube that goes out a window, put it in the front living room and that made a difference for sure.
 
Quote from: Utclmjmpr on July 20, 2019, 05:21:19 PM
Most folks don't understand that normal cooling with A/Cs won't do better than about 20 degrees cooler than outdoors.>>>Dan
Click to expand...

wackymac said:
Isn't that suppose to be cooler than the inside air temp?

Also it makes a big difference on what color the outside of your vehicle is.
Click to expand...
Well, the cold air coming out of the air conditioner should be at least 18-20 degrees cooler than the temperature of the air returning to the air conditioner.  However with windows, not very good insulation, and especially the windshield, just because the air coming out of the A/C is cool there may not be enough of it to keep the rig cool.
 
Utclmjmpr said:
Most folks don't understand that normal cooling with A/Cs won't do better than about 20 degrees cooler than outdoors.>>>Dan
Click to expand...

That would depend a LOT on the heat gain of the conditioned air space...the inside of the MH.  You might be confusing the standard of a 20 degree difference between outlet air and inlet air on an A/C unit.  Generally speaking, about 20 degrees difference between what goes into the return air duct and comes out of the A/C outlet is about all you can hope for.  If the M.H. or whatever is insulated well enough to keep heat from infiltrating to the inside, you could easily see 30 plus degrees of differential between outside air temps and inside air temps.
 
I agree, but for 30 degrees, that's going from 100 outside to 70 inside, and all I got to say, you better be under a shade tree.  :))
 
I really don?t understand why, in light of the high tech insulation items we have today, heat gain thru the roof continues to be the problem it is.
 
Pilothawk said:
I really don?t understand why, in light of the high tech insulation items we have today, heat gain thru the roof continues to be the problem it is.
Click to expand...

Simple Economics 101.  It costs money for something not easily seen, and many of us State Park weekend campers don't typically care, we paid for a spot with unlimited electricity.
 
Pilothawk said:
I really don?t understand why, in light of the high tech insulation items we have today, heat gain thru the roof continues to be the problem it is.
Click to expand...
In addition to Spencer's comments, insulation doesn't usually STOP heat transfer, it just slows it down, depending on the rating -- weight and space (you lose ceiling or cabinet height with more insulation) are also factors.
 
I forgot to mention that I also put in ceiling vent/skylight insulation covers which makes a significant difference in preventing cool or heat loss through the thin vent plastic.

Here's what I purchased: https://smile.amazon.com/gp/product/B0024E6QX0/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
 

Attachments

  • RV vent insulator.jpg
    RV vent insulator.jpg
    83.5 KB · Views: 7
I really don?t understand why, in light of the high tech insulation items we have today, heat gain thru the roof continues to be the problem it is.
Click to expand...
I don't think the roof itself is a problem, at least not in mid & upper grade rigs. In the less expensive models, the R-value of the roof is typically lower so probably a contributor to the problem.  Regardless, skylights and roof vents are popular and they are just gaping heat holes.  Our last coach had  a 6" thick roof with excellent insulation, but 3 Fantastic vents plus a huge skylight over the shower.  We carried 3 vent pillows plus a foam insulation panel with velcro straps for the shower skylight and used them when we had to park in full sun. Made a huge difference in the a/c run time and interior comfort.
And then there are the side walls, side windows, windshield if a motorhome, doors that get opened repeatedly throughout the day, etc.
 
You must log in or register to reply here.

Latest posts

Members online

Total: 469 (members: 6, guests: 463)

Forum statistics

Threads
131,964
Posts
1,388,314
Members
137,717
Latest member
aquaticvegetation
Back
Top Bottom