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From: (no name) (no email)
Date: Mon Feb 03 2003 - 13:29:14 EST
In a message dated 02-Feb-03 19:36:52 Eastern Standard Time,
writes:
> I would appreciate recommendations on what size of marine air unit would be
> substantial enough for a 28' boat, in Florida?
> Then what size inverter and battery bank would be needed to power it
> overnight at anchorage...recharging the bank the next day while running the
> main engine with a dedicated alternator for the separate bank..also what
> size alternator?
> Thanks,
I have a 16,000 BTU unit that services the aft section of Bandersnatch which
is about two or three times larger than the interior of a 28 foot sailboat
and is about 70 % insulated. I would think that a 8,000 BTU unit would do on
a 28 foot sailboat with white hull and deck in average conditions. I would
recommend a reverse cycle unit so you could use it to take the chill off
winter mornings. We have this and it works well in St Augustine in the
winter.
As for inverter. I am not aboard right now to see if I can start and run my
16K BTU unit with my 2.5 KW Trace inverter. If you send me an email in a
week or so I will try it. But I imagine a 2.5 KW would work a 8K BTU AC
unit.
As for batteries. I recall my 16K BTU AC runs at about 16 amps at 120 vac.
Perhaps we can presume a 8K BTU unit would run at half that, 8 amps, which
would be 80 amps at 12 volts, plus about ten percent for inverter loss so 88
amps times 12 hours for a hot, sultry, Key West night is 1056 AH. Assuming a
50% discharge floor this would require a battery bank of about 2200 AH.
Using 220 AH golf cart batteries it would take 20 golf cart batteries, 10
pair in parallel, to run the 8K BTU AC for 12 hours.
As for an alternator to recharge the batteries, I would suggest the largest
alternator you could physically mount and drive. Using two v-belts off the
crankshaft, this seems to be around 200 amps. And, of course, an external
regulator. Anything bigger would have to have a Power Take Off (PTO) to avoid
too much side strain on the crankshaft bearing. A genset with a very large
battery charger would also work and have the advantage of working when
plugged into shore power.
Norm
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