Air conditioners/heat pumps

[scanzel]

I am still trying to decide on roof top or basement air units and I am wondering how much heat does the heat pump version put out as far as temperature. I realize they only work good down to about 45 degrees but is the extra cost worth or is it better to just provide more supplemental heat by another source and skip the heat pumps all together. I was planning on either the Coleman basement unit or the Carrier low profile units which both have a heat pump version.

[DavidInWilmNC]

The heat pump models are not much more expensive than the normal A/C's (+- $100 or so).  Mine (a Carrier 15K standard model) also came with heat strips, which don't do a whole lot.  Mine puts out a lot of heat 'til the outside thermostat cuts off the compressor and switches to the heat strip.  I believe the switchover temp is actually around 38° from what my thermometer tells me.  It's not really cold here too often, so the heat pump works well; even so, you'll likely need either a diesel or propane furnace / boiler if it gets down much below 40°.  I don't really see it as an either-or kind of decision, but more of an 'in addition to' type of thing.  You can get a lot of heat for a little electricity with a heat pump. 

David

[cody]

We have 2 carrier 15K units w/ heat pumps, they work well for 90% of the time, it's when the temp gets down below 40F that we have to add some additional heat, usually a small electric heater.  My only gripe is the fans are a little on the loud side so when we're in the living room area, we turn on the bedroom one and at night we use the living room one, it works well for us that way.  We have a center isleway so the heat moves pretty well.

[Jerry Liebler]

Steve,
     You really should also consider a ductless minisplit heat pump that was/is normally used in residential situations.  The equipment for residential use is subject to federal regulations and because of this comes much closer to delivering the rated performance.  Additionally RV equipment is rated for cooling capacity at 80 degrees outside temperature while the residential units are rated at 95 degrees.  The difference in rating temperature usually means that at 95 outside a 12,000 BTU residential unit will do more actual cooling than a 15,000 BTU RV unit and because of mandatory efficiency requirements do it with about 1/2 the power use.  I have an 18,000 BTU residential minisplit heat pump in my bus, it cools the whole bus to 75 with outside temperature of 103, sitting in bright sun and does it on 13 amps of 120 volt power.  Also, my heat pump works  down to 0 degrees outside, producing about 12,000 BTU of heat at 0.  The residential minisplits have defrosting functions to allow operation at below feezing outdoor temperatures.
Regards
Jerry 4107 1120

[NJT5047]

I've got two rooftop heatpumps and they are good, as has been stated for down to about 40*. However, they are great down to about 45*.  That last area causes them to to start doing something that I would guess is defrosting.  The fan cuts off and they sit there and makes funky noises.  Then after the odd cycle completes, the unit resumes heating. 
The units don't do the "defrost cycle" as long as the outside temps are above 45*.  The fan turning off wakes me up...bummer.  One heat pump is all that is needed for our bus.  The front unit is all that I typically use.   A coach must have an open floorplan to get away with that. 
They are excellent for 90% of our camping...early spring and late fall.  They are useless in cold weather. 
The good part is that the campground is supplying power. 
An insulated coach will heat with two small ceramic heaters. Even with outside temps in the 20s.
A poorly insulated bus isn't any fun at all in sub-freezing weather.  A bus has to built for cold weather camping.
zJR
 

[Frank @ TX]

Hi Scanzel,
As you know everybody does it the way they want.
We knew that we would be caught in freezing weather ( by our chose or not ) from time to time.
As been stated heat pumps have a low temp limit cut out.
We choose to get 3 AC's on the roof and an AquaHot in the bay.
The Aquahot has an electric heater built inside that makes hot water for showers and heating.
The electric element alone will heat the bus with outside temps in the 20s.
When the temp goes lower it kicks on the diesel burner as an automatic function.

So we thought we'd put the extra $ of the heat pump toward the Aquahot instead.
The "Compfort Center" by Dometic does a great job of controlling both systems.
But do it like you want to, this is just what we thought to do with ours.
Frank

[Skykingrob]

Hi Steve
I put 2 of the Coleman heat pumps (2 compressors in each unit) in my 91 XL and a 45K Aquahot. I have done test runs inside my shop and have needed 3 or the 4 units to cool the coach in 100 degree/90% humidity Missouri. Coleman tells you the key is plenty of return air and dropping the cool air from the ceiling with the return on the ceiling. It took quite some time to figure out how to do that but I believe I have accomplished it. I really like how quiet the basement units are, but there will be times in RV campgrounds when it would be nice to cover up a noisy campground with A/C noise. It is a trade off.
When I bought my units, the heat pump and the regular a/c were the same price. I got surplus stock, $795 each, from Winnebago through Colaw RV Salvage at 1-417-358-2125 in Carthage, MO. That is quite aways from you and don't have the name of a salvage place closer to you. I do like the sound of the mini-splits that Jerry talks about and I think Nick uses them. Nick is closer to you, is an a/c guy and so he may be able to help. If you choose to go with the Colemans and would like to talk about the ducting, email. I would certainly be willing to help any way I can.

Rob
91 LeMirage XL
Missouri

[Nick Badame Refrig/ACC]

Hi Steve,

If your looking for a clean roofline, then the basement HP is a good choice. Jerry and Rob mention the ductless split, this also will work but

in my eyes, the looks of the inside unit and the space needed for the condencers, is non functional for me. I have installed 9 ductless splits

to date in bus conversions, and from a mechanical stand point they are just not built strong enough or designed to be in a moving vehicle.

The design of the condencers makes it an extreame space eater when you have 3 to install in a coach. The airflo needed to cool the compressors

would mean having well more then 1 compartment open to the outside enviroment for cooling.

  The coleman and the Dometic units are designed for a compact space and I'm not saying they are efficient, or reliable, but over the years and

2 1/2 years of personal testing in my bus has sold me on the design reasons. Theese basement units are quiet, [no noise at all in your bus]

and all the mechanical componets are in the bay so there is also no water to worry about draining off either.

Good Luck with your choice
Nick-