Air Conditioning - Split A/C Unit and 2 Wires to Thermostat

This concerns a York split A/C unit in our condo in Mexico. There are no standard wire colors as in the United States to apply color coded wires to be specific terminals for a specific installation. The compressor is outside and the air handler is inside the condo. There are two wires from the compressor that go to the air handler: one is connnected to the fan and the other is connected to a capacitor that is mounted on the fan. There are no wires from the air handler that are connected to the thermostat. The wires to thermostat directly run from the contactor in the outside compressor unit.

I want to install a digital thermostat. The voltage to the old thermostat is higher than the 24v needed for the newer one, which will require a step-down voltage unit.

My problem is that none of the diagrams show anything for a 2 wire A/C hook-up and I do not want to assume that what I see to be ok, is Wrong, ruining the new thermostat.

New Thermostat Terminals:

G Fan
Y Cooling
W Heating
Rc Air condtioning power
R Furnace

Metal Jumper intact on R and Rc

Are the terminal wires to be used Y and Rc without any jumper(seems way too simple, thus creates doubt)

Thank you

Half the color wire here are not what they should be. It pays to check it all the time.
Lets go this way an you check it all out. First the ac units all work with a 24V transformer so will read 30V . All low Volts tstat work on 24V to 30V. Find the transformer. Now one wire off it has to go to R on the tstat. The other side of it or wire has to run to the contactor on the condenser and to one side of the blower relay in the inside of the blower unit in the home. Now from the tstat a wire on Y has to go out to that contactor in the condenser unit. Then a wire on G has to go to that fan relay in the inside blower unit. This way when you call for cool both the outdoor unit and the inside fan unit turn on. On the tstat you have fan on. so anytime you turn this on just the fan will run.
Post back in same post here if you dont get it.

ED;)

[QUOTE=Ed Imeduc]Half the color wire here are not what they should be. It pays to check it all the time.
Lets go this way an you check it all out. First the ac units all work with a 24V transformer so will read 30V . All low Volts tstat work on 24V to 30V. Find the transformer. Now one wire off it has to go to R on the tstat. The other side of it or wire has to run to the contactor on the condenser and to one side of the blower relay in the inside of the blower unit in the home. Now from the tstat a wire on Y has to go out to that contactor in the condenser unit. Then a wire on G has to go to that fan relay in the inside blower unit. This way when you call for cool both the outdoor unit and the inside fan unit turn on. On the tstat you have fan on. so anytime you turn this on just the fan will run.
Post back in same post here if you dont get it.



Before I go out and retrace the wiring, please clarify one point about another thermostat: As I have taken the old thermostat completely off the wall and it only has two wires,can a new digital faced thermostat be installed?

Thanks

Well yes and no. Does it need a common or batteries????? You can just run 2 wire . But that way you can only make the power go to the condenser and turn it on. But you can turn the blower relay on from the 2 wires that go to the condenser contactor.

ED ;)

Since the old thermostat activates both the compressor outside and the fan of the airhandler inside the condo at the same time, a two wire hook-up works. So if the new thermostat terminals are:

G Fan
Y Cooling
W Heating
Rc Air condtioning power
R Furnace

Metal jumper currently to R and Rc
New thermostat is a programmable for 24 Vac single stage heating and cooling systems, battery-powered,isolated heating and cooling circuits.

Would the terminal hook-up for the two wires to the new thermostat be Y and Rc without the jumper?

Thank you

Yes RC to Y will work

The R and RC are in there for if you have a transformer to run the heat that would go to R and another out in the AC unit then its power would go to the RC. If you have only one thansformer to run both then you put that jumper from R to RC