I have a Lennox 2.5 ton heat pump along with a CBX32M air handler.
What i'd like to do is install a backup generator. A pretty large one
(22KW) but not large enough to power the heating system with the
electric backup heat which is 15KW in itself.
Can I just wire the compressor, and the air handler itself through the
transfer panel to get basic heat/cooling without the electric backup
heat? My theory being that it should be sufficient as long as its
not very cold outside. if that happens, then we can add space heaters
If that is possible, I think my problem is that the blower motor in
the air handler is wired in with the electric backup elements. Is
there a way to separate the blower and perhaps put it on the
compressor circuit instead, so that I can power that through by
transfer switch panel on a fairly modest ampacity circuit (about 15A
for compressor and 1.7A for the blower)?
On 9/7/2010 6:28 PM, email@example.com wrote:
I've setup systems like that in the past and the best way to do it
is through the control system. The way I would do it is have a relay
with normally closed contacts that will break the control circuit
for the heating element contactor whenever the generator is running.
It's not rocket surgery but you need to understand control circuits.
Simply interrupt the control side of the strip heat ( IOW the 24 VAC
control to it ) with a small relay with a 120VAC coil, use a NO
contact, and power that coil as 'always on' from a non-transferred
On Mon, 13 Sep 2010 04:41:56 -0700 (PDT), " firstname.lastname@example.org"
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On 9/13/2010 6:41 AM, email@example.com wrote:
Well duh! < me. It can be separated inside the unit without too much
trouble. The darn heat strips and air handler will draw more than
65amps alone at 230VAC. The diagram I found online shows what would
have to be split off. I would install a control relay to lockout the
heat strips to prevent any possibility of power back feeding through
the system via the electric heat relays when the main power goes out.
If you wanted to get a bit fancy, you can install a latching contactor
of the type used in many transfer switches and lighting controls that
will stay on until getting a signal from your transfer switch to open
the circuit to the heat strips. You may have a more detailed wiring
diagram that came with your unit than the one I found online. Of course,
when splitting the power, pay attention to the phases and
make darn sure BOTH power sources are disconnected when any work is
done on the air handler.
For a 2 1/2 ton heat pump, you don'g need 15kw strips in the first place.
All you need is 10kw. Also remember that in heating mode you will have
defrost cycles that will be running both the compressor and the strips at
the same time.
FWIW, those plug it in the wall heaters average 5kw each. That defeats the
Time for him to install gas logs and a propane tank. Of course, I wonder
what fuel the generator is running on. I remember back in the middle of
the last century when all electric homes in this area were considered to
be the cleanest and most economical to heat. 8-)
Clean electric. What a hoot. Just means that the pollution is some
where else, in the power grid. Back in the seventies, my area got a
nuclear power plant. Which is fine with me. They were talking about
how clean the power is. Cleaner than coal, I'm sure. Just hope they
figure out what to do with the radioactive stuff after it's used.
An example of non polluting clean power. Is to go to the woods and set
up a gasoline generator, run a couple hundred feet of cord. The point
of use has no pollution.
I saw one blowing over the wet floor at the airport. Of course
it was using 277V.
Ah, can't find that one, but:
has lots of high output, portable units.
You _do_ have 440 service to your living room, right?
Knowledge may be power, but communications is the key
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