How many btu's for a basement a/c?

[ilyafish]

Online guides are saying 9,000-10,000 should be fine.  I will only be using this when not in motion and will be using my OTR a/c while underway.

Thanks guys!  Time to go rip up my floor

[John316]

Ilya,

Are you sure that you want basement air? What about roof air? I am just curious because if your basement unit goes out (I know you guys with basement units...it never happens ) you don't have air. If you have four or five 15,000 btu Due therm Dometic low profile units, and one breaks, no big deal. The band is happy because they can sleep, you are happy because all you have to do is take it down and get it fixed.

Just some food for thought.

Merry Christmas,

God bless,

John

[TomC]

My 40 x 102 bus has three 13,500btu Coleman roof airs.  I do not have any other a/c, but with 2.25" sprayed foam insulation, usually two do the job fine and one will keep everything cool once the sun is down.  If you use basement air, one 27,000btu (double 13,500btu unit in one) would be my choice.  Remember during the day lots of heat can come in just sitting still.  Good Luck, TomC

[John316]

Right on Tom!!!

Merry Christmas,

God bless,

John

[JohnEd]

Ilya,

I am sure with John and Tom.  You need redundancy....especially in a system that will make the bus not habitable.  

The roof airs/heat pumps are the easiest to install and replace and many advocate for them for that reason.  If you duct them they are quiet enuf but less efficient.  Does not take up any basement space.  You will need two so three seems prudent.

The home stuff is more efficient but some say that they won't stand up to RV use.  There isn't much in those units that can flop around so I am a little skeptical that they won't last.  The only home units that have been used are the "Mini Split".  I think that is the way to go and I suggest you install two of the 27KBTU units and put one heat exchanger in front and one amidships.  Lots of choices so be careful for the best deal and quietest operation.  Uses no ducts.  read up on these.

Basement air is popular but it needs ducts and uses a bay.  Nick has two in his bay and I think they are heat pumps.  He has all the info and sells the basement airs.  No reason not to buy from him especially considering the support.

You can't size these things using "HOME" formulas.  Beside simply need more BTU you have the added consideration of needing to col the bus down FAST ater a heat soak.

HTH

John

[sivrtnge2]

I have 3 basement heat pump units. I love them. My only drawback is heat. My coach is total electric and I have toe kick heaters. I would love to have one of the diesel fired units for heat as well as to help start this beast in the winter.
--
BILL

[Nick Badame Refrig/ACC]

Hi Ilya,

Merry Christmas!

The average basement A/C or HP system is 15,000 btu's for the single and 27,000 btu's for thr twin system.

With that said, the avarage car A/C system is around 5 tons [50 to 60,000 btu's] tonnage is very important for moving vehicles.

The heat gain in the sun, the traveling speeds in the wind, and the ability to cool off a 100 deg. + temp when parked in the sun

is calculated inti every vehicle on the road. If you notice that it usually takes 5 min's to cool off your very hot car and it could take

as much as 4-6 hours to cool off your home in the same temps should tell you something.

Good Luck
Nick-

[Len Silva]

I have had both and presently have two roof units.  I will never have another coach with roof units.  The noise, the vibration and the dripping water have turned me off forever.

[belfert]

10,000 BTUs won't even make a dent, particulary on a hot day if you have large windows (like my bus).

I only have a single 15,000 BTU unit in the front area of my bus and I might add another one because one doesn't do much on a hot day.  I have spray foam in ceiling and walls, but I also have four 3' by 4' windows.

[John316]

I have had both and presently have two roof units.  I will never have another coach with roof units.  The noise, the vibration and the dripping water have turned me off forever.

Len, that is interesting. We haven't had any problems with ours. What model do you have? What brand? I am just curious, because we will want to steer clear of those in the future. We have five 15,000 btu penguin Dometic Low profile roof airs (my dad always said go for redundancy ), and we love them. I just wondered why you didn't like yours.

Ilya,

Also, get a roof sealant, like Dicor  http://www.rvupgradestore.com/browseproducts/Dicor-EPDM-Rubber-Roof-System-Lap-Sealant.HTML roof sealant. That link is from a quick Google search. We sealed every single rivet on the roof of our coach. Otherwise you might have a little leak somewhere, and you don't want to fix that later, once it has ruined everything.

JAT

God bless,

John

[Len Silva]

John,

Admittedly, they are 1994 models, both Dometic.  Perhaps just replacing them would make a difference, I don't know.

I had basement air in my 4104 and it was whisper quiet just like at home.

[John316]

Len, Thanks the explanation. Basement units probably would be quieter.

God bless,

John

[JohnEd]

Ducting the roof airs will quiet them down a lot.  In your design make way to allow the opening of the duct right under the unit....much more efficient that way if you get in a bind somehow.

John

[niles500]

If you use "basement" units just make sure they're rated for Marine or RV use - HTH

[PP]

We've had both and I couldn't agree more with Len. Rooftops were noisy, water running off the roof, vibrating the whole coach. The latest experience was with 2000 Coleman Mach's. The others were on an older SS. We currently have three basement air and their effecient, quiet, couldn't ask for better. But we're planning on removing the front one to make room for a hide-a-way TV. Just my 2cents worth.
Good luck, Will