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-   -   Help with wiring onf HVAC system (http://www.diychatroom.com/f17/help-wiring-onf-hvac-system-80760/)

viper 09-07-2010 01:21 PM

Help with wiring onf HVAC system
 
Oh this one should get all the pros worried..:thumbsup:

I am curious about signal wiring of the thermostat and most importantly the condenser. I have my 2, 120V contactor wires coming from the condenser but where in the air handler do they go? Also, there are some taps in the handler Marked, W, R, G, C, etc. I do NOT like to simply rely on color matching to wiring things. I wanna "know" how this thing is wired.

I do have the schematic for the system in my hand but does not indicate a voltage on half of the stuff and certainly does not include an output for the condenser coil contactor. Where does this power come from? There just does not seem to be enough wires to get this all done.

I guess maybe 3 is all that is needed? Request for heat, request for cool, common.... Maybe I am over complicating this..

fabrk8r 09-07-2010 01:30 PM

Quote:

Originally Posted by viper (Post 497271)
there are some taps in the handler Marked, W, R, G, C, etc.

Those lugs are for the low voltage (24V) thermostat wiring. Does your schematic show the thermostat connections?

viper 09-07-2010 01:39 PM

I do see where the Tstat wires in but reall does not tell me which is what so I guess going to have to go off what is here.

I still do not have any clue where the outputs are for the condenser. That should be a 120V source?? Looking at the wiring in the condenser, there is 2, 18ga-ish wires to the main contactor and wires led back to the air handler. (used system that I am reinstalling). Because this is a heat pump, the wiring is probably much more complicated that it should be and I still do not know how the heat pump system is initiated. Has to reverse the system somehow and 1ph motors do not like to reverse so I would assume some type of diverter valve in the condenser somewhere.

viper 09-07-2010 01:49 PM

EDIT: after taking another peek, that latching coil in the condenser main contactor is actually 24V. I am looking at the wiring for it right now. Looks like there was probably supposed to be several wires to the blower unit to control the heat pump system and looks like that has already been bypassed because it was controlled with 2 wires. I can see where they are headed but just do not see what they should tie to in the air handler.

fabrk8r 09-07-2010 02:37 PM

Condensing unit/heat pump should be 240V.

There will be a 110V reversing valve inside the condensing unit. You can usually see it if you look down through the fan. It will have 2 wires on it's quick connector that come out into the unit's access panel area.

Do you have 5 conductor thermostat wire from the air handler/furnace to the condensing unit?

viper 09-07-2010 04:31 PM

Quote:

Originally Posted by fabrk8r (Post 497319)
Condensing unit/heat pump should be 240V.

Yes, I realize. The main power to the condenser is 240V. I am only referring to the signal wiring. ie, contactor relay.

There will be a 110V reversing valve inside the condensing unit. You can usually see it if you look down through the fan. It will have 2 wires on it's quick connector that come out into the unit's access panel area.

Do you have 5 conductor thermostat wire from the air handler/furnace to the condensing unit?
There is only 2 wires coming from the condenser and I can tell the heat pump side has been bypassed thus the 2 wires. there is 18/2 going from the condenser to the furnace. Just need to know where to get my 24V to turn on the condenser.

Please read above.

beenthere 09-07-2010 05:37 PM

Quote:

Originally Posted by fabrk8r (Post 497319)
Condensing unit/heat pump should be 240V.

There will be a 110V reversing valve inside the condensing unit. You can usually see it if you look down through the fan. It will have 2 wires on it's quick connector that come out into the unit's access panel area.

Do you have 5 conductor thermostat wire from the air handler/furnace to the condensing unit?

Residential heat pumps don't use 120 volt reversing valves.

viper 09-07-2010 06:41 PM

Yeah, it would have to be 24V or 240V because those are the only 2 voltages at the condenser. common is not carried to the condenser so 120V is not used.


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