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Old 03-28-2016, 01:33 AM   #1
Join Date: Aug 2010
Posts: 30
Year: 1986
Coachwork: bluebird
Engine: Int. DT466
Rated Cap: 35
AC advice

hey everyone.

I'm looking for some advice on AC units. Ive been told to get one of those standard rv roof unit that runs on 120V, requiring a generator or shore power due to the large draw. but isn't there a 12V option? I keep seeing sprinter vans and the occasional (apparently in-service) school bus with roof mounted units... they cant have generators on board can they? I've been looking for some definitive answers about this for a while now and it seems like everyone has their own truth.
I'm looking to find out whether theres a realistic 12V air conditioning option, or if i have to accept the standard rv style 110/120V units, and if so, What is the best type of low profile unit? my bus is only 25 feet long but gets blazing in the mid summer sun. it's well insulated with spray foam.

thanks in advance for the advice
kyletheyeti is offline   Reply With Quote
Old 03-28-2016, 09:15 AM   #2
Join Date: Mar 2010
Location: Texas
Posts: 214
Year: 1997
Coachwork: AmTran
Chassis: Genesis
Engine: DT466
Rated Cap: 84
DC air conditioners tend to be 48v or 72v due to the massive power draw. They are also rather expensive.
Timelord is offline   Reply With Quote
Old 03-28-2016, 10:21 AM   #3
Bus Crazy
Join Date: Jul 2011
Location: Winlcok, WA
Posts: 2,225
The ones you see on Sprinter vans and other kinds of buses have an engine driven compressor. In other words, the only time they work is when the engine is running.

Regardless of whether or not it is a AC or a DC powered unit, in order to run an A/C unit without running the engine, gen set, or shore power it is going to take a huge battery bank to keep up with the power draw an A/C compressor uses. And at the end of the day, if you don't have a huge solar array to replenish the battery bank you are going to have to plug in or run something to recharge for the next day.
cowlitzcoach is offline   Reply With Quote
Old 03-28-2016, 11:34 AM   #4
Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 14,384
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
another possible option if you think A/C will be your only High-power item is to look into a Pro-Pak or similar device.. its not cheap

but its basically what Semi-drivers are using now as many municipalities and rest areas prohibit main engine idling for trucks..

typically a unit consists of a 2 cylinder diesel engine, a belt driven A/C compressor, a coolant loop that can be tapped for Domestic cabin heat, and typically an alternator (usually 12 volt, but can be bought 24)..

this device would give you A/C, heat (if you want it), and enough power to keep your 12 volt system charged and operating your low voltage appliances.. (run an inverter for your TV's, computers, etc)...

the engine in it is small enough (typically smaller than a reefer engine) that it is allowed ot be idled anytime.. and Yes you can run it while you are driving your bus if you wish to run the A/C, and fail to have Dash A/C.

the compressor in it is typically a sanden variant so you can run the appropriate matching rooftop or skirt mounted condensor, and then either a basement ducted, or a side / rear mounted evaporator unit... I believe you can outfit them with the sanden 5xx or 7xx (larger capacity) compressor...

again its not cheap but its an alternative to a rather large genset (for an electric A/C unit you need a large gen to handle the compressor start surge).. or having to let your main engines run...

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