DDoyle9570@aol.com wrote:
> The A/C is 208 volt 3 phase, 60 cycle. It has a 28.5 amp requirement.
> My question is what size generator will be needed to power this?
Do you know whether 28.5 amps is the start-up surge, or the
steady-state operating current? My 1965 TM 9-2320-209-10 says that the
air conditioner circuit breaker is a 20-amp thermal circuit breaker,
which suggests to me that the A/C pulls a rated 28.5 amps when the
compressor turns on, but quickly settles down to under 20 amps once
the compressor is up to speed.
That current specification is probably the per-phase current. Using
the 28.5 amp surge current for a conservative estimate, the A/C power
requirement is:
120 volts * 28.5 amps per phase * 3 phases = 10,260 watts
Thus, a 10 kW generator like the MEP-003A diesel set that I just got
on Ebay would just barely run the air conditioner! (Its actual rating
at sea level is 34.7 amps per phase, or 12,492 watts).
> What size would I need to also power the few (8 two bulb fixtures)
> fluorescent lights in the van body?
What is the wattage of the bulbs? If they're 40 watt bulbs, for
instance, they'll use an additional 640 watts, which is not too big
compared to the current draw of that A/C.
If the van had a main power supply fuse or breaker, I'd suggest that
the generator should be sized to supply the full current rating of
that fuse/breaker. My old TM implies that there is no master breaker,
so I'd add up the current values of the 120 volt breakers, then add
three times the 28.5 amp surge current, and multiply that all by 120
volts to get the minimum generator size. I recommend using the A/C's
surge current, not its running current.
Assuming that my TM correctly represents your truck (which it may
not):
* 2 20-amp circuits
* 10 15-amp circuits
* 2 28.5-amp circuits for A/C
==> 275.5 amps * 120 volts = 33,060
That suggests that a (conservatively-rated) 30 kW generator should
supply the maximum power requirements of your van.
Now, if you don't plan to run any heavy equipment other than that air
conditioner, a 15 kW set may be sufficient for your needs. That would
leave 5 kW of headroom for lamps, a fridge, a microwave oven, etc.,
even during the A/C's turn-on surge. I noticed that Coleman's Surplus
has a 15 kW diesel set on a trailer listed on their web page
(www.colemans.com). I haven't done business with them before, so don't
take that as a referral! :-) I'd guess that it's an MEP-004 generator,
and it looks like it might even have the acoustic suppression kit.
I hope that helps!
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