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From: donn@neurad.UUCP (Donn S. Fishbein)
Newsgroups: net.consumers
Subject: Heat pump/water heater energy conservation
Message-ID: <237@neurad.UUCP>
Date: Wed, 11-Dec-85 15:30:02 EST
Article-I.D.: neurad.237
Posted: Wed Dec 11 15:30:02 1985
Date-Received: Fri, 13-Dec-85 08:46:19 EST
Reply-To: donn@neurad.UUCP (Donn S. Fishbein)
Organization: Natl Inst Health, Bethesda, MD
Lines: 40

Having recently moved, and for the first time having to pay energy bills
directly, I have several questions about the most efficient use of an
electric heat pump and electric hot water heater.

First, the manual for my heat pump recommends setting one temperature and
making no further adjustments.  Is it more economical to set back the
temperature at night, and during the day when no one is home, or to leave
the temperature adjustment alone?  Is there something unique to heat pump
technology in this regard?

Assuming that temperature set-back is economical, I have noticed that nearly
all of the automatic thermostats available specifically say "NOT FOR HEAT
PUMPS".  After diagramming the existing thermostat and one automatic
thermostat (Magic-Stat 3000), the major problem seems to be that the heat pump
contains two thermostatic switches; one for the heat pump compressor, and one
for the aux. heating coils.  The heating coils are activated if one changes
the temperature set point abruptly eg. from 55 F to 68 F.  Does this occur
simply to decrease the time it takes to achieve the new temperature,
or is the heat pump incapable alone of affecting the change?  Is it more
economical to allow the heat pump to operate alone?  (NOTE: I have not seen a
situation yet where the heat pump alone could not maintain a temperature,
but I realize that if it is too cold outside the coils will be needed. )
Is there a solution to this problem of automatic thermostats being unable to
control an essentially two-stage system?

Finally, with regards to the hot water heater, is it advisable to install a
timer so that it only runs when people are likely to be home.
In other words, is the energy needed to reheat the water more or less
than that required to maintain the water temperature for a prolonged period of
no hot water use. My hot water usage is quite modest, yet I think this
appliance is quite an energy hog.

I realize that I have posed many questions, but I would appreciate hearing
from those with experience in these areas who can answer any or all of these
questions.  Thank-you


-- 
Donn S. Fishbein, MD  (N3DNT)   (301)496-6801
..!{harpo,allegra,decvax,ihnp4}!seismo!neurad!donn