CSLB C-20 HVAC ContractorControls, Electrical and SafetyEasy
On a standard 24-volt thermostat, which terminal is used to energize the indoor blower relay for continuous or fan-only operation?
- AC
- BR
- CW
- DG
Show answer & explanationAnswer & explanation
Correct answer: D. G
The G terminal controls the blower relay (fan) circuit. R supplies 24V power, W calls for heat, and C is the common return wire for powered thermostats.
Why the other options are wrong
- A. C is the common wire that completes the circuit for powered thermostats/displays.
- B. R is the 24V hot/power terminal, not the fan terminal.
- C. W energizes the heating circuit, not the fan.
Thermostat G Terminal
The G terminal on a low-voltage thermostat energizes the blower relay, allowing the indoor fan to run independently of heating or cooling calls.
- G = Green wire = fan/blower relay
- Used for 'Fan On' switch position
- Works alongside Y (cooling) and W (heating) calls
Memory trick: G is for 'Go, fan, Go!'