"Terry K" wrote in news:1151068708.100276.227550
@m73g2000cwd.googlegroups.com:

Why does not every a/c unit include provision to use it as a heater?



Most have strip heaters in them, or have it an available option.....

A heat pump needs, well, heat to function well. Here in the South we
heat our homes with heat pumps. But, alas, they only work good down to
about 40F outside air temperature, then the evaporator (the outside unit
of the reversed cycle) starts to freeze up requiring us to temporarily
reverse it again to boil off the ice that forms on the outside coils.
They call it "Defrost Cycle". I've always called it "Freeze Your Ass
Cycle" as really COLD air comes out of my vents when it's going on.

Boats with heat pumps work great in Charleston because the water from the
Atlantic is always WARM, even in January. The water never gets below
about 50F for long, so the warm water pumping through the water-cooled
heat pump keeps it from freezing up. If a water-pumped heat pump ever
DOES freeze up, say from the creepy crawlers plugging up the seawater
strainer, for instance, or the seawater pump failing, an amazingly fast
block of ICE forms INSIDE the seawater heat exchanger, which is just
tubing, after all. This ice, of course, does what ice likes to do,
expand and rip open any "pipe" it freezes in, including the amazingly
expensive seawater heat exchanger.

Another reason I don't like it is the damned maintenance, especially
going to the boat in winter to clean the creepy crawlers out of the
strainer so often. Even in winter they colonize a strainer here as they
get sucked in. One good reason for that is the ones trapped in the
strainer are warmer than the ones outside the boat, I suspect. They seem
to relish in the warmth of the strainer.

Electric heat, heat strips, suffers from none of these problems. When's
the last time you took your electric heater apart to clean it out?
Mostly never?

Now, economics. Noone gives a rat! They're paying for dock space with
50A of 120VAC for a god-awful amount each month. If the electric bill on
the boat is $200/month or $20, who cares? Boaters with electric meters,
excepted, running strip heat in the boat simply drops marina profits.
It's cheap heat when someone else is paying for the power to run
it...especially if you factor in the boater's expense of heat pumps,
maintenance, the damned seawater pump that has a MTBF of 150 hours,
cleaning out strainers on a freezing, deserted dock on Feb 2nd in the
gale.

It's not an issue "Up Nawth", anyway. With a seawater temperature of
33F, the heat pump is nearly useless as its seawater heat exchanger
freezes below the water freezing point and it either has to do frequent
reverses of the cycle to deice it or just freeze it solid.....