Hi, Looking for a answer to Nest Quandry.

[pjg43]

Hi,
I just installed a Nest. My control board is a EWC-ST-2E. Now the heat portion of the thermostat works fine. The cooling however is a different story. After a few calls to the NEST folks its been established there is a low voltage condition between Y and R. I checked the Transformer and 26V is leaving so I know thats good. Theres also 25V at the transformer block on the board but 18V between Y-R on the thermostat block also between w-R I have 25V. So (After a lengthy description
) am I safe to assume I may need a new control board?
Thanks for any info,
Peter

[Paul Z.]

That board is not conpatable with that thermostat. You will need to replace it with a NCM-300. That board is a master control relay board that needs a thermostat having a "O" - "B' terminal which the nest does not have, nest has a O/B terminal. Please call if you have any more questions.

[Waheed123]

) am I safe to assume I may need a new control board?

[Paul Z.]

You need two change board to an NCM-300. Your board is the old master stat and will not accept the newer stats.