How do you power a roof air?

[ojgetaway32]

Coleman 13,500 BTU...

[thomasinnv]

you may want to elaborate on that question a little bit.  do you mean how to run wire to it?  or what type of power?  or how to connect it?

[ojgetaway32]

Good point.  Simply put, ignoring running wire etc, what should one use to produce the electricity whilst motivating down the road?

[thomasinnv]

most people just run the onboard genny while driving.  there are a few that run it off inverter while driving, but you will need to make sure you have enough amperage from your alternator to do it that way.  the oem alt on most of these buses are north of 200 amp which is plenty.  make sure you match the inverter voltage to your system voltage. (12 or 24v)

[bevans6]

Here is my recent thread on exactly how I power my 15Kbtu roof air on the road.  I decided I didn't want to run my generator, since it is a gas generator not really intended for use in an RV, so i went with a pure sine inverter.  The link is my detailed description of exactly how I did that, what equipment I used, and how I wired it all up.  It works  flawlessly.

http://www.busconversions.com/bbs/index.php?topic=16972.0

Brian

[TomC]

Usually when you need A/C going down the road, you will need to run at least two roof top airs to keep the entire bus cool.  The simplest is to just run your on board genset to power them like I do.  The more complicated way is to run them with the inverter and large battery pack (powered by the large 50DN alternator @ 27vdc [270amps @ 27vdc {when the engine is running} equals 7290 watts]) like Sean does.  You ultimately will use more fuel running a second engine for the genset over the extra drag on the main engine to run the A/C's by the inverter.  Good Luck, TomC

[Len Silva]

Using the 50DN and an inverter seems to work very well in a 24 volt coach.  Trying to do that in a 12 volt coach I think might be problematic.   You might squeak by on the road but any idling or heavy traffic time is going to draw down the batteries.

[bevans6]

To expound on Len's point, a 24 volt 50DN puts out a nominal 270 amps for the 6500 watts.  It's 12 volt version puts out a nominal 300 amps for around 3600 watt's, a tad over half as much power.  To run two roof airs (I only run one, but I don't cool the whole bus, just the front half) you need 4000 watts of inverter, and will draw right on about 3600 watts when both are running, so that's why you would be marginal.  I agree a gennie is probably a better solution for a 12 volt bus.

Brian

[TomC]

It was interesting to note that when I bought my 2500 watt inverter, I was thinking of stacking them to get 5,000 watts to power the A/C going down the road.  The gal that sold me my inverter asked if I had a Diesel genset, and I said yes.  So rather then trying to sell me a second inverter, she said to just run the genset for the A/C and use the inverter for incidental small loads.  The two large loads I do have wired through the inverter are my bathroom wall heater and my primary water heater.  All are inductive electrical loads (meaning no motors) and are not of the continuous run type.
Running my 300amp 50DN produces 14.1 volts which equals 4230 watts.  Even so, I keep with running my A/C straight from the Diesel genset.  In 15 years-no problems.  Good Luck, TomC

[Sean]

...  All are inductive electrical loads (meaning no motors) ...

Tom, I think you meant to say those were "resistive" (non-inductive) loads...

-Sean
http://OurOdyssey.BlogSpot.com

[BUR]

     I run the front air off of the inverter going down the road with no problem. When  I get to where traffic might stop for a while, I will start the generator. I have 2500 Prosine 24 volt inverter and seems to work  good. The problem I have is dry camping. The inverter only puts out 50 amps max charge and with 8 group 31 AGM's it's just not enough charge.      Good Busin' Wilbur

[TomC]

Your right Sean-resistive loads.  Inductive loads would be all motors.  Thanks, TomC