Selecting roof airs

[andy]

I've been looking at 3 differant roof airs with heatpumps. I thought with heat pumps I could get by until I could afford the webasto unit. The Duo-Therm says for use in temps 40 degrees and up. Carrier says basically the same thing. Coleman on the other hand dosen't say if it will operate at lower temps can anyone shed some light on the subject.  Thanks for your input. Andy

[Nick Badame Refrig/ACC]

Hi Andy,

40 deg. is the normal cut off for all heat pumps before they become inefficent and freeze up.

Most RV type HP's don't have a defrost cycle to melt a frozen coil, they just shut down.

Heat pumps make good sence when you have wabasto type diesel fired heat. In mild temps you can

save diesel fuel by having the electric source, and vice versa....

Nick-

[Ross]

Roof airs usually have electic heat strips....Or are they making one now with a heat pump?  If memory serves, the heat strips are rated in BTU, and they don't put out much.

Ross

[andy]

yes they are making heat pumps that are capable of 15000btu of heat

[NewbeeMC9]

Ilike the low profile Carrier AC with recovery from Condensate evaporation.

Get a slow speed fan or you'll have regrets.

Mine came with colmans, they are loud without slow speed and the heatstrips a dont workwith the high speed fans.


get the ones with higher BTU and lower amps to limit more troubles

if you have to have roof airs thats my $.02 let us know what you go with too.

[andy]

Thats a good point I do want somthing quiet are there any more opinions it all helps to make an educated purchase.

[NJT5047]

I've have two Dometic heat pumps that have worked great.  They will provide plenty of heat down to a little less than 40*.  Above 40*, they make much hotter heat than my home heatpump...which is good.
Be aware that the heat cycle uses just above 15 amp to operate, while the AC cycle uses between 11 and 13 amps (per unit). 
These are real heap pumps and not the little 7k heat strips.  Heat strips are about useless.   Heat pumps have no heat strip backup such as is used in home heat pump units.
Also have LP backup furnace...just in the unlikely event I'm caught in real cold conditions.   
Dometic heat pumps are 15k cool, 12K heat.  They are wall thermostat operated, are zone capable, and have low and high fan speeds.  The low speed is not especially noisy, but high is.  Still, it feels good in hot weather.  Keeps the air circulating.
My units have been used a right good bit on AC for 3 years...going into the 4th season. 
These units are pretty low profile compared to some.  We painted the covers and they don't really look that bad.  MC9 is just over 12' with air suspension inflated.  No raised roof. 
Raised roof generally rules out rooftops.   
If this pix works, it'll show the height of Dometics. 
Best, JR

[DavidInWilmNC]

I've got a 15K Carrier heat pump on my MC-8.  It puts out quite a bit of heat until the temp drops to around 38 outside.  My bus is still in the construction phase, and there is a lot of exposed metal (those alum. panels on the wall), which conduct quite a bit of cold.  If I leave the unit on overnight, it will be nice and toasty inside (around 72) with outside temps around 40-45.  Starting with a cold bus, the heat pump takes a while to warm up, especially when it's close to 40 outside.  Otherwise, it heats quickly.  I'd recommend two - for redundancy and quick heat.  I'm not sure of the current draw on mine, but I could check it.  I have it on a 36' 50 amp cord going to a 25' 30 amp cord plugged into a 20 amp outlet.  I can have lots of lights on, a circular saw, drill, or sander, and the heat pump and it's never tripped a breaker, so it doesn't seem to pull too much current.  The Carriers also have a 1500 watt heat strip, but it doesn't do a whole lot of good. 

David

[andy]

I live in Indiana if I left for Fla. in Dec and the temp here was 20 or below the heat pumps would not do me much good if they dont work below 40

[NJT5047]

Andy, that's what the LP is for.     A Webasto or Proheat would also be nice.  The beauty of heat pumps is that it's free heat when plugged in...as long as it ain't your outlet.
At today's diesel prices, diesel fired heaters are not a bargan, although they work very well. 
As long as the bus is running, heat isn't an issue.  Bus heat will keep you plenty warm. 
As a guage to what it takes to warm a bus, we left for Arcadia in December and it was about 24 degrees the night before our departure.
I wanted the bus warm when we left (4:30A) so left a small 1500 watt ceramic heater running inside.   I knew the heat pumps wouldn't heat at those temps and didn't see any reason to burn LP. 
The bus was comfortable with the tiny little heater next morning.  Two of these little electric heaters will heat a bus.
If you plan to be plugged in most of the time, electric backup is good...if not, some sort of LP or diesel fired unit will be necessary.  You still have to have ACs, and the heat pumps work in any condition above 40 degrees....most of Florida in the winter.
This discussion is interesting in that there are so many ways to do utilities, yet no "best" way.
Post what you decide to do...I'm interested.   
Best, JR

[DavidInWilmNC]

I live in Indiana if I left for Fla. in Dec and the temp here was 20 or below the heat pumps would not do me much good if they dont work below 40

You would be correct if it never got above 40.  Do you have spring and fall (seasons)?  Will you be travelling to more temperate areas?  If so, then you could use the HP's.  Besides, mine was only about $100 more than the 15k AC only unit. Think of heat pumps as a secondary source of heat, and you'll be fine with them.

David

[NJT5047]

Just one more thing...an RV style LP ducted furnace like I'm using is a quiet, nice operating system.  It makes good heat, and heats a cold bus within a few minutes.   
The ducts have to be planned (should be planned) so that there are areas to run the ducts from front to rear.  There are 4,  4" outlets. 
A wall mounted thermostat controls the unit.  Runs on 12V.     
I'm using a 31 k Hydroflame.   Comparatively, LP is a good bit less expensive than diesel fuel.   
I don't know what your RV experience may include, but these heaters are good primary heaters, are not expensive, easily repaired, and parts are everywhere. 
If you plan to have LP, this is a reasonable option...if not, Webasto or Proheat, Aqua Hot has your heater.   Two upright 40 lb tanks are more than enough LP for most RV use.  They'll easily fit into a corner of a bay.   It'll also keep your fridge, hot water and range going...alas, that's another subject.   
BTW, have you priced a Webasto lately? 
I promise...I'm done!  JR

[TomC]

While I have 3 Coleman roof airs with heat strips, the heat strips do work, but have to give them time and in the meantime is blowing cold air-which is irritating.  If you are not inside and just want to warm the bus over about 20 minutes, all three on will warm the bus nicely.  What I don't like about the Colemans is that they have just 2 speed fans that are like high and medium-which is still noisy for night use.
For plugged in, I use two electric portable heaters that for the most part keep the bus warm down to about 40 then the furnace has to be used.  The price for 2 or 3 portable heaters is much less than the heat pump option on the A/C.  You then keep the A/C simple without the diverter valve for the heat pump function, and also can easily replace the portables when the time comes.  Good Luck, TomC

[muddog16]

I've been trying for the last year to find someone to purchase the new Carrier Low Profile HP's that are ducted from......and I'm not having any luck.  I've even called Carrier, talk about a nitemare, do any of these companies have humans left to talk to on the phone?    I like the idea of 7.5" profile at present with their lack of availability the clearances are even better............If anyone could help I would definately appreciate it! Thanks

Pat

[Dallas]

I've been trying for the last year to find someone to purchase the new Carrier Low Profile HP's that are ducted from......and I'm not having any luck.  I've even called Carrier, talk about a nitemare, do any of these companies have humans left to talk to on the phone?    I like the idea of 7.5" profile at present with their lack of availability the clearances are even better............If anyone could help I would definately appreciate it! Thanks

Pat

Pat,

Here are some things Cat, (the better half or 7/8ths in most cases), has taught me about getting through to a human on computerized systems.

These don't always work, but it's worth a try:

As soon as the other end picks up:

Press 0
or press 00 really quick

press *0

Press *

Press 4 or 5 (this came up the other day)

Press 0000 before anyone can start talking or the recording can begin.

There are more, but these will get through about 80% of the time.

Another one to try is not to press anything, sometimes an operator will come on eventually to see why that line is lit up but not connected anywhere.


Good luck