"Vic Smith" wrote in message
...

On Fri, 30 Jan 2009 04:52:40 -0500, "Eisboch"
wrote:



My current boat has two reverse cycle AC/heat units. The Navigator had
four of them. Marine types exchange using water rather than ambient air
and
surprisingly, there is still enough heat in the ocean water up here during
the winter for them to produce enough heat to keep the boat nice and warm.
I usually shut them down and winterized them before the deep cold set in.
If I had stayed on the boat all winter, like some others do at our marina,
I'd would have used them throughout the entire winter. I know a few
people
that live on their boats year-round at the marina and they have told me
that
there is only about a 2 week period in the middle of the winter when they
have to supplement the heat pumps with some electric space heaters.

Didn't know they were that good.
You ever look at the efficiency trade-offs at different temps?
Like when it's more efficient to use the space heater, even though the
pump can do the job.
I wonder if those motel thru-wall units are heat pumps. Had to turn
the heat on in one of the motels on the way to Florida last year, and
I just assumed it had heat coils. But maybe not.
From what I've read it's too cold up here to make heat pumps a frugal
investment.

--Vic

Some of the reverse cycle heat pumps have strip heaters also. I suspect
hotel types use strip heaters in the heat mode. One of the units on the
Navigator was equipped with heaters. You could program it to run using the
compressor in the reverse cycle mode or using the heat strip.

The water based systems seem to run pretty well down to water temps of 40
degrees, then start to lose ground if the water temp goes lower. They will
still extract heat, but not as efficiently.

Obviously, an air exchange system won't work with air temps even higher.
Our pool heater has an interlock to prevent it from running if the ambient
air temp drops to about 45 degrees or less.
If it continued to run, it would simply ice up the evaporator.

Eisboch