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HVAC Controls Wiring

Thread starter GreenEE
Start date Jul 10, 2009

Status: Not open for further replies.

Jul 10, 2009

GreenEE

Electrical

Regarding the wiring/design of thermostats using NEMA codes. Could someone confirm my understanding of how B & O change over lines are supposed to work. I am especially interested in the which power source (RC or RH) supplies B & O

O is powered from RC when cooling is needed (does it mirror Y)
B is powered from RC when heating is needed

Is this correct?

Should G be powered from RC or RH?

Thanks