<VV> Heat Pumps

[JVHRoberts at aol.com]

I think you need to check out what the state of the art is capable of. Heat  
pumps with two stage/two speed/variable speed compressors can go MUCH colder 
and  still put out good heat. In fact, check this one out:
 
_Energy  Innovations ~ Cold Climate Heat Pump electrical specs_ 
(http://www.energy-innovation.com/products.php?mode=prd&prdid=9)  
 
For most of us, running electric backup is fine, since there's not that  many 
days where it's cold enough to need it. 
 
In a message dated 10/23/2005 10:19:35 P.M. Eastern Standard Time,  
pp2 at 6007.us writes:

>In  regard to heat pumps,  those which are air-to-air (the usual) require  a
>fairly warm winter  climate

Lowest I have seen in Orlando  was 17F about a decade ago. More often we 
just hope for a few days below  freezing to curb the bug population.

That said, we have a 50,000 btu  heat pump for the house that is much more 
efficient than the 36,000 btu  unit when we built the house cooling the new 
500 sq ft addition without  any problem. The monthly bill in summer went 
down considerably when it was  installed so they have gotten much more 
efficient..

Heat pumps  themselves are good to about 20F and have electric coils 
(resistance heat)  for lower temperatures. Before we had the new one 
installed, I had the  electric strips disconnected for years and we never 
really noticed. We  also have heaters in the ceiling fans in the bedrooms 
which I run on the  low setting (800w) for really chilly nights.

The basic problem is that  the heat cycle is basically an a/c in reverse and 
the outside air must  warm the coils to function. Once the air temperature 
gets down to the  working temperature of the heat pump, transfer stops. Most 
still use R-22  Freon which limits the working temperature just as high 
outside  temperature limits the effectivity of the a/c. With the right 
medium you  could get heat at far lower temperatures but it would cost a bit  
more.

So for temperatures down to about 20F, a heat pump can be  effective and the 
EER is a whole lot beter than resistance heat but once  it gets colder they 
do not work so well and "help" may be  needed.

Padgett