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CF100 Questions

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Posted by phillb on March 12, 2010, 12:21 pm
The Grumman Sunstream CF100 Solar Hot Water heater I have is old, the
storage tank is rusting and the control box is on the frits to often..
I want to change to a storage tank that has a heat pump within it, but
no one makes this
Seems like the only thing to do is get another storage tank and also
get a tank-less water heater

I have tried to find manuals for the CF100, I think they have all been

Any pointers of what could be done from someone out there

Or just sell the collectors, and upgrade?

Posted by phillb on March 13, 2010, 11:49 am

Be good for efficiency though
Use less of the Heat Pump

Posted by Josepi on March 13, 2010, 12:16 pm
 I am surprised we haven't seen much of this.

Possibly make the solar hotwater heater system usefull 100% of the year.

A small heat pump shouldn't make that much of a cost increase from the usual
price gouging.

Be good for efficiency though
Use less of the Heat Pump

Posted by Malcom \"Mal\" Reynolds on March 13, 2010, 8:06 pm
 In article

That may be true, but remember that the
other side of the heat pump is pumping
out "cold" that can be vented into your
HVAC which makes it run less

Posted by Robert Scott on March 14, 2010, 12:30 am

Well, here is one way in which solar energy can help out a heat pump:

Heat pumps operate with a Coefficient of Performance (COP) of between 1.0 and
maybe 5 or 6 at the maximum.  The COP is ratio of heat produced to electrical
energy consumed.  When COP equals 1.0, you essentially have straight resistance
heating.  When COP is 4, then you get hot water using only 1/4 the amount of
electrical energy that simple resistance heating would require.

The main factor affecting the COP is the temperature of the source where the
heat is being pumped from.  That source can be either ambient air or water from
a well or some other source.   For example, for my space heating I have a
geothermal heat pump using a closed loop with 2000 feet of plastic pipe buried
in my landscaping.  When the incoming water from the loop is 50 degrees F, then
the COP of my heat pump is about 4.0.  When the incoming water drops to 33
degrees F, as it does in late January, then the COP is down to about 1.4.  And
if the incoming temperature drops much less than that, then the heat pump simply
stops working.

So imagine a heat pump system where low-grade solar heat (say 60 deg. F) is used
by the heat pump to keep the COP up.  Under some conditions, such a hybrid might
be cost-effective.

Robert Scott
Ypsilanti, Michigan

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