Chromalox incremental heat pump

[Sledge]

Hi all, I hope someone can help.

I am working on a

Chromalox
M#SHPIDF1504.0
S#86041269
15000 BTU cooling
13650 BTU heating
with an electric heating coil for emergancy heat

This is an air to air heat pump.

The deal is that this unit has had a lot of hands in it, and has no wiring diagram.

My experience is almost non-existant on air to air heat pumps.

I am thinking that there has to be some kind of defrost control on this thing...to defrost do we run the a/c so that the outside coil has some heat to work with?

Would anyone happen to have a wiring diagram for this thing. Of course it is urgent

[back2space]

Whats actually wrong with the unit. The defrost mode basically is the cooling mode except the indoor blowers are usually off.

[Sledge]

I struggled through and made my own diagram. I have a kink in my back, from sitting hunched, peering into a 6 x 8" junction box, containing 3 relays, 3 time delay sequencers, a low temp control, a transformer, and a chaotic mess of wires.

What I discovered was that the way it was wired, it couldnt have worked, there is no defrost timer, and the low temperature control was wired to shut off the heat pump, and run aux heat when the temp was below 35F....which means no operating below freezing...so it is off cycle defrost.

So much for the cost savings of a heat pump when it is below 35F outside.

[momo]

Do not be surprised at your findings, optional defrost components often appear on system sold to Russia and cold contries. Especially economy kit which skips on the complication of the cycle back2space mentioned. You have worked out with back pain what is usally programmed into the chips controling heat pumps a/c's - most times we do not get that near to knowing how the thing is run !!