Thermostat Wiring Carrier AC Split System

[drewdin]

I have a question about the wiring in my Central AC, I have a Nest thermostat and recently I had an issue during the recently cold weather we had.

When we had the -10 degree week, my nest lost power. I found that my carrier condensor has a thermal cutoff where when it get too cold it cuts power to the system to prevent it from running. This cut the power to the thermostat and I didn't have heat. Nest Support said that I needed to add the common wire from the system to the thermostat but I only had three wires.

So I went and purchased a 5 wire thermostat wire, and replaced the existing wire. Everything was fine until i opened up the carrier AHU to wire in the new 5 wire.

I noticed that there are two thermostat wires going into the AHU, a two wire from the condenser and the 5 wire from the thermostat. The way the system is currently wired, The condenser is run in series with the white wire from the AHU to the thermostat.

This might be the correct wiring as during the past summer the AC worked fine but seeing the condenser wired in series does not look right for me. I though the wires would be landed differently, to the thermostat or something. I have the AHU wiring diagram and current wiring in the included pictures.

You can see the thermostat wire at the bottom of the picture with the green wire wrapped around it is the condenser wire.

Can someone let me know if this is the proper/normal way that condensors are wired?

Thanks!

 

[drewdin]

not a word from no one?

 

[nealtw]

word 1
but not much help

 

[user 4883]

Is this a heat pump / Ac ?

 

[drewdin]

no heat pump, forced hot water with a Boiler and AC.

 

[user 4883]

at the thermostat jumper Rc & Rh, also connect the red wire from the air handler to either.
connect the yellow wire to Y1.
Connect the white wire to W1.
Connect the green wire to G.
In the air handler switch the white and yellow thermostat wires.
Use the green A/C wire for Common, connect it to the blue wire nut with red and white wires.
Connect the other end of the green A/C wire to C on the thermostat (if you cant find the other end then you could use the blue wire on the other cable).

 

[drewdin]

so I did a ton of research and I had it wired wrong. I found an image online that was my exact setup. The first thing I did was rewire the thermostat and AHU using the correct color wires for the type. Then I wired it per the included diagram and it works like a charm.

Initially I just needed to add another wire to the common and bring it to the NEST. I guess I took the round about way to do it.