On Thu, 29 Jan 2009 21:54:02 -0500, "Eisboch"
wrote:


wrote in message
...
On Jan 29, 8:24 pm, "Eisboch" wrote:
wrote in message

...

If you have a small cabin on a boat can you get a small heat exchanger
that heats in winter and cools in summer that runs on 12 volts? What
kind of system would you use?

No.

Eisboch

So how do they air condition boats and campers?

My smart ass answer was because you said "runs on 12 volts". You would
have to have a battery bank the size of the boat to have enough amp capacity
to run a heater or air conditioner for very long. A small AC unit will draw
roughly 8 amps at 120 volts, so figure more than 10 times that using a 12
volt compressor (if they made one) or running it from a 12vdc to 120vac
inverter.

Generating enough heat BTU's would be a similar current draw. 12 volts is
simply unrealistic.

Air conditioners on boats or campers run from either 120 volts and in rare
cases, 220 volts.
The power is supplied from a genset or shore power.

Campers usually have either a heat strip in the AC unit and/or propane
heating systems.

Propane heat and maybe something like this for 12V A/C.
http://www.arcticbreeze-truckac.com/...eezeintro.html

But you're still going to need a genset for the A/C unless you have
120v service and an inverter.
Might be better/cheaper then to go with cheap 120v home window unit.
Larry has recommended these kind of setups and you can google his
solutions.
The Mac 26 forum had a number of guys installing A/C, and they all
went the shore power/genset 120v window unit route.
See what the ice-fishing guys uses to heat their ice shacks.
I know nothing about heat pumps, except the temp differentials often
make them non-cost effective.

--Vic