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Posted by SteveB on December 25, 2007, 5:43 pm
> SteveB, not exactly sure what you are asking about the power
> requirements. Normally, you have a 240volt circuit run to the outdoor
> unit, ideally sized according to the information on the tag on the unit.
> Then a separate 240 circuit to air handler to power the heat strips and
> the blower, with the breaker and wire sized according to the size of the
> heat strips, which can typically be between 3 and 20 Kw. A lot of units
> with 15kw and larger strips have the strips split into 2 circuits. The
> strips will come off and on with the outdoor unit running if the
> thermostat determines they are needed. They also typically are energized
> when the HP goes into defrost so it does not blow cold air.If the
> thermostat is turned to "emer heat" , the outdoor unit does not run, and
> the blower and heat strips are used, so that it operates just like a
> regular electric heat system. Again, dunno if this answers you question
> or not. Larry
Yes, it does. It sounds like I'll need another circuit just to power the
heat strips. I was wondering if one or the other worked at any one time,
like the heat strips OR the compressor, and, apparently, they run at the
same time, plus all the power draws of the blower.
Steve
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Posted by J.A. Michel on December 24, 2007, 3:49 pm
> My house has a Rheem heat pump, installed in 1991 Model #RPND-042C, with
> "Heater Kit RXPJ," according to its nameplate. Temperatures are about
> 35-40 degrees F this time of year where I am.
>
> Often in the morning the heat pump blows cold air for a half-hour (or
> more?). I had an HVAC service tech out here a week ago. He could not find
> anything wrong.
>
> Does it simply take a while for the refrigerant to get to suitable
> temperatures for evaporation/condensation operation when in "heating"
> mode?
>
> What symptoms might I observe that indicate the unit needs a charge of
> refrigerant?
>
> Also, I would like an operating manual, hopefully with a layperson's
> troubleshooting guide. Although I am pretty handy and I would prefer to do
> electrical side troubleshooting myself. Anyone know where I can get such a
> manual for this unit? I tried both the Rheem and Ruud sites; no luck.
>
Heat pumps blow colder hot air than a regular furnace will.
Some folks (like me) hate heat pumps. If it bothers you that much,
can the HP and get a real furnace. That's what I did.
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Posted by Elle on December 28, 2007, 5:45 pm
> My house has a Rheem heat pump, installed in 1991 Model
> #RPND-042C, with "Heater Kit RXPJ," according to its
> nameplate. Temperatures are about 35-40 degrees F this
> time of year where I am.
>
> Often in the morning the heat pump blows cold air for a
> half-hour (or more?).
Further update:
Last night I set the thermostat at 68 degrees F. Overnight
the outside temperature got down to about 38 degrees F. I
woke up about 5 AM to a freezing house and cold air blowing
from the registers. I waited 15 minutes, and cold air was
still blowing out.
At the thermostat's thermometer, the room temperature
reading was 62 degrees F. I then turned off the heat pump.
Freezing my rear off, I pondered it all. I let ten minutes
go by, set the thermostat at 63 F, and then turned the heat
pump back on. Cool air blew out for a minute or so, and then
warm air followed, and the house warmed. Over an hour or so,
I raised the thermostat setting to 71 F or so. The house
continued to warm, and all was well.
The same HVAC technician that came out a few weeks ago came
out again today. This time he determined that the reversing
valve was sticking. Obtaining a new valve will take a week
or so. Meanwhile he said if cool air was blowing out again
when I wanted heat, then switch the thermostat from heat to
cool, and then back, and listen for a "swish" sound. This
might jar the valve free and cause it to open(?) properly.
Any advice on helping ensure my house has heat in the days
remaining until the new valve arrives and the tech can
install it? I will continue with the "gentle touch" when
raising the thermostat setting. Perhaps the mechanical
features of the valve respond better to less extreme
electrical signals?
I know the basic function of the reversing valve. But I am
not sure whether it (1) throttles the refrigerant at all or;
(2) it's always wide open for heating mode, and wide open
for cooling mode, just directing the refrigerant flow in
opposite directions depending on the flow; or (3) switches
between the two directions when in heating mode, as a part
of the defrost feature?
I think understanding this might help my dealing with it in
the days before the repair. TIA for any light anyone can
shine on this. Meanwhile, I will google.
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Posted by lp13-30 on December 28, 2007, 8:03 pm
Elle, you are correct on #2 & 3. When a heat pump goes into defrost,
three things happen-- the reversing valve switches to the cooling mode,
the outdoor fan shuts off, and the OD unit sends a signal to the air
handler to turn of the heat strips to prevent it from blowing cold air.
Your valve may be sticking in the cool position. Hopefully the tech
carefully checked out the defrost controls and is sure that is the
problem. (replacement of a reversing valve is very expensive) On most
heat pumps, the valve is in the heat mode when there is no voltage to
the solenoid coil on the valve, and power to cool. For some reason,
Rheem/Ruud units are the opposite. They have to have power to heat. If
he found voltage to the coil, and the valve still in the cool mode,
then his diagnosis sounds correct. Good luck Larry
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Posted by Elle on December 28, 2007, 9:58 pm
> Elle, you are correct on #2 & 3. When a heat pump goes
> into defrost,
> three things happen-- the reversing valve switches to the
> cooling mode,
> the outdoor fan shuts off, and the OD unit sends a signal
> to the air
> handler to turn of the heat strips to prevent it from
> blowing cold air.
> Your valve may be sticking in the cool position. Hopefully
> the tech
> carefully checked out the defrost controls and is sure
> that is the
> problem. (replacement of a reversing valve is very
> expensive) On most
> heat pumps, the valve is in the heat mode when there is no
> voltage to
> the solenoid coil on the valve, and power to cool. For
> some reason,
> Rheem/Ruud units are the opposite. They have to have power
> to heat. If
> he found voltage to the coil, and the valve still in the
> cool mode,
> then his diagnosis sounds correct. Good luck Larry
Hi Larry, the technician said he alternated voltage to the
reversing valve and found it sticking. He may very well have
done something more sophisticated (or simply what you
indicate above) but did not want to explain it (on his
admittedly valuable time) in too much detail to someone
unacquainted with heat pump systems.
A few weeks ago he did check the defrost controls, and, beg
pardon, replaced the defrost control board, though initially
claiming nothing was wrong. This happens to be the second
board in a year. I think the technician knows what he is
doing, since, as you suggest, the board is a lot less
expensive to replace, and they do fail often (from my
reading on the net). On the other hand, two in a year seems
excessive, and I wonder if the sticking reversing valve was
overlooked in both cases, so as to avoid the expense. I am
on a home warranty here for the heat pump, so I can't blame
them too much. I'd hope the cheaper item was the problem as
well, if I was DIYing it.
I think I follow what you mean (in your other post) about
what the tinkering s doing. It's maybe keeping the heat pump
from getting that 30, 60, or 90 minute signal to defrost. At
least, that's what I remember from reading on the net
earlier and a few comments from the technician on this. What
you propose does seem to explain the symptoms of the
problem. I will try again the "gentle touch" of just upping
the thermostat a degree from room temperature at a time,
starting around 5 AM, when no doubt again cold air will be
blowing due to the reversing valve being stuck in "cooling"
mode while defrosting. After that, as the sun rises, I think
I won't need defrost any longer for the day and will
continue to adjust the thermostat upwards every hour or so.
Or I will come up with some similar plan. It seems to me I
want to let it get into defrost mode and remove frost, then
deal with the valve sticking by cycling the controls a bit,
worst case.
Thank you for sharing your experience. It helps a lot.
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