OK Larry, you don't need to chime in and make me feel even more
foolish. I did something wrong in my head with that calculation.

Damn, where is that calculator?

--

Roger Long



"RW Salnick" wrote in message
...
Roger Long wrote:
The AC element on my hot water heater is 1250 watts.

Can you safely draw from an inverter while the engine is running?
If I put in a 1500 watt inverter and used it carefully to only run
the water heater (which would also be getting waste heat from the
cooling water coil) and was sure that my other 12 V loads were
minimal at the time, could I get my hot water tank heated up in the
5 - 10 minutes that I do with shore power? (It takes motoring half
a day to do it with the waste heat alone from my 20 hp diesel).

Or, will this burn up my little 35 amp alternator? I have a 55 I
can put in but it needs a different voltage regulator.

I would never try to make hot water from the batteries through the
inverter for obvious reasons.

Your 35 amp alternator puts out 35 amps x 13 volts (approx) = 455
watts. Your 80 amp alternator will deliver 1040 watts... both
running flat out and probably overheating. Neither would supply the
1500 watts your heater needs, or the approximately 1700 watts your
inverter would need to make the 1500 watts your heater needs. Not
even both together would be enough.

Further, this electrical energy comes from the mechanical energy
that the engine develops. 1700 watts represents about 2.25 HP, or
in your case, about 10 % of your engine's maximum output. If you
are not running at full throttle, you could be delivering as much as
25% of your engine's output to the alternator(s). Much better to
use the waste heat in the cooling water loop - that is free from an
energy standpoint.

bob