I'm swapping thermostats from White Rodgers 1F97-1271 to Sensi WiFi thermostats, and verified that my best bet was to perform a board upgrade from my EWC-ST-3E to an NCM-300, specifically so that I can gain a C wire to power the stats at the wall. I have an American Standard Freedom 90 Single Stage Condensing Gas Furnace (AUX060C936D) and American Standard Comfort Coil (Universal Heat Pump / Cooling) (TXC036C4HPC).
I have attached a picture of the current setup. The damper motors and zones 2-3 are pretty self explanatory. I'm interested in making sure I wire up "SYSTEM", the zone 1 thermostat and the dip switches correctly given there are some differences going from the ST-3E to the NCM300.
* For SYSTEM I currently have Y, W, G and R. Y and G are self-explanatory. R connects to either Rh or Rc as they are jumpered. I believe that the previous W wire is connected to W1/B?
* For the zone 1 stat I currently have W, Y, R1, O, B, G. I believe I wire W -> W/E, Y -> Y, R1 -> R, G -> G. I previously had separate wires for O and B though, and they are connected to the existing thermostat. The current White Rodgers zone 1 thermostat is configured in "heat pump" mode, and I have a picture of that wiring as well:
Note that like the board, the new Sensi thermostat only have a single O/B terminal, not independent terminals:
For dip switches, I believe that I have to set dip switch 1 to "heat pump" and dip switch 2 to "heat pump" thermostats.
It would be great if someone could confirm this wiring for me. Thanks!
Upgrading EWC-ST-3E to NCM300
Upgrading EWC-ST-3E to NCM300
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Re: Upgrading EWC-ST-3E to NCM300
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Re: Upgrading EWC-ST-3E to NCM300
I configured as I had originally described, but wired the original system W to new W2/E rather than W1/B. Everything appears to be working fine - the system is ultimately controlled by master thermostat 1, though my other 2 zones may call for heating / cooling as before. I did notice that the dampers seem to be "open", even when no zone is calling for heating / cooling. I'm not sure if that behavior is different from the old board, or if I'm just noticing it more because of the LEDs that are showing.
I also verified that the C wire was working properly by removing the batteries from all of the thermostats and hooking them up to the wall - they all powered up properly.
The other thing I noticed is that when all stats were set to "cooling", the compressor LED came on, but my outdoor condenser didn't spin up. I assume the board is functioning properly, and that there's a problem elsewhere in the system. Last summer the condenser was having problems starting and I had an HVAC tech come out and get it going (I live across the country, and had a tenant, so had to take their word for it rather than investigate myself). They seemed to think the condenser might need replacing soon, so it's possible that thats the problem.
I also verified that the C wire was working properly by removing the batteries from all of the thermostats and hooking them up to the wall - they all powered up properly.
The other thing I noticed is that when all stats were set to "cooling", the compressor LED came on, but my outdoor condenser didn't spin up. I assume the board is functioning properly, and that there's a problem elsewhere in the system. Last summer the condenser was having problems starting and I had an HVAC tech come out and get it going (I live across the country, and had a tenant, so had to take their word for it rather than investigate myself). They seemed to think the condenser might need replacing soon, so it's possible that thats the problem.