Community Forums

sailorman1 · 07-18-2021, 08:27 AM

Can you run living space air conditioning while driving as I don't see a standard engine being able to do it?

Are typical RV alternators high enough capacity to run an AC via an inverter.

wolfe10 · 07-18-2021, 08:29 AM

Roof A/C's are 120 VAC and with (very) rare exception (read that $$$), can only be run from either shore power or generator.

Podivin · 07-18-2021, 08:33 AM

Yes, most of us that travel in hot weather will fire up the generator so that we can run the roof air conditioners. That's the only way to have any chance at all of arriving with a decently cool RV.

sailorman1 · 07-18-2021, 09:14 AM

So people drive with the generator running?

What are typical sizes of roof top AC units?

I can run my boat AC off the batteries and inverter, just not very long before running down my batteries. But a 200+amp alternator on a RV and a 2-3000W inverter on a 300HP RV doesn't seem a big deal to my know nothing brain.

MSHappyCampers · 07-18-2021, 09:18 AM

We run our generator and both A/C units when traveling in hot weather!

twinboat · 07-18-2021, 09:50 AM

Quote:

Originally Posted by sailorman1

So people drive with the generator running?

What are typical sizes of roof top AC units?

I can run my boat AC off the batteries and inverter, just not very long before running down my batteries. But a 200+amp alternator on a RV and a 2-3000W inverter on a 300HP RV doesn't seem a big deal to my know nothing brain.

Your going to need about 160 AMP@12 volts for each AC, thru your inverters.

You will need over a 350 amp alternator but then the engine belt can't handle that kind of load, long term.

The answer may be a mini split AC system. They reportedly draw less current.

PDR John · 07-18-2021, 10:05 AM

Gennys need to run regularly, so I start it up before we leave on each trip. We always arrive with a cool coach.

rk911 · 07-18-2021, 10:15 AM

you’ll need to run your generator in order to run the roof AC. we do it all the time.

Alpine36 · 07-18-2021, 10:20 AM

In extreme heat we run the dash air and generator with roof air set to zone1, the front one. Make sure to set your dash air to recirculate for best results. The alternator/inverter/house batteries will not efficiently run the roof air for any length of time before bad things start happening.

Jon_C · 07-18-2021, 10:22 AM

Quote:

Originally Posted by sailorman1

So people drive with the generator running?

What are typical sizes of roof top AC units?

I can run my boat AC off the batteries and inverter, just not very long before running down my batteries. But a 200+amp alternator on a RV and a 2-3000W inverter on a 300HP RV doesn't seem a big deal to my know nothing brain.

I run 1 roof air on a 340 amp alternator and inverter while driving. Ran 4/0 cables to alternator and inverter. Adds a little load on the motor (diesel) but no issue.

BillJinOR · 07-18-2021, 10:31 AM

I’m sure someone will develop or use new mini split inverter ac for motormen in the near future. Your standard alternator will not be enough or seriously over stressed for today’s roof top ac units . . That and ac’s are not wired into the inverter to even be able to run them without complete rewiring in my case the inverter panel is in the basement and the main panel on an inside cupboard 20’ apart , a real pain to re wire even if I wanted to
For now just run the darn generator, most people I know do ! it was made to be run while in motion or not .plus …. It needs to be run to keep the elect windings in good shape. That’s what it’s there for! I guess There are those that put up curtains etc to just use only the dash ac but my opinion is I want the entire coach cool. Trying to leave the generator off to save 2 or 3 gallons of diesel kind of defeats the whole multi thousand dollar coach comfort purpose.

KanzKran · 07-18-2021, 10:41 AM

Quote:

Originally Posted by Jon_C

I run 1 roof air on a 340 amp alternator and inverter while driving. Ran 4/0 cables to alternator and inverter. Adds a little load on the motor (diesel) but no issue.

My van doesn’t have a generator, but it does have a second alternator for the house system. I run the roof air off the 3kW inverter when driving if it’s needed, though the front air is usually enough, and also when stopped for lunch using battery power. It’ll run for hours on high off the battery, and all night if it isn’t too hot and it can cycle.

I wouldn’t attempt to use the standard chassis alternator that the chassis manufacturer supplied, though. It’s got enough to do, and probably wasn’t designed to output rated power for an extended period. My 270A second alternator never quite gets to 200A, and usually will sit around 150-160A when running the roof air. That’s just under 3 hp (electrical) at 14V, and probably close to 5 hp input with belt losses and electrical inefficiency. Not much of an extra load on the engine.

KanzKran · 07-18-2021, 11:54 AM

I forgot to include a photo that’s representative of Sprinter second alternators; not my photo. It has its own belt, so it’s not adding load to the existing.

There are kits out there for various other vehicles. Don’t know about DP’s or Ford powered Class A chassis, though, but never had a reason to look into it, either.