R to g

johnjohn89

Guys what should u reading voltage between r to g during the heating mode? 28v or ov? Some unit I work on when during the heating mode I do get voltage readings between r and g, other I don’t , but I do believe that g get power by other , doesn’t power same time 

ratio

Depends on how the control board is built. Some may back feed the G terminal when the limit turns the fan on, some may not.

pecmsg

If a switch is closed you get 0 voltage
if a switch is open you get voltage

HVACNUT

There's so many different ways to wire the fan for heat mode. Some will use G, and some won't. 
A PSC motor could get direct line volt power from an aquastat, or an internal time delay relay.
A variable speed could get voltage on W1 and start the fan. Voltage at W2 will increase fan speed. 

The wiring you see where G is powered for fan in heat mode is usually done at the thermostat. There will be a "gas/electric" switch, or it will ask during installer setup "equipment or thermostat controls fan in heat mode".

johnjohn89

ratio said:

Depends on how the control board is built. Some may back feed the G terminal when the limit turns the fan on, some may not.

That’s what I looking for thanks

pecmsg said:

If a switch is closed you get 0 voltage
if a switch is open you get voltage

depends on what energized the blower, some unit r and g not energized by thermostat, 

johnjohn89

HVACNUT said:

There's so many different ways to wire the fan for heat mode. Some will use G, and some won't. 
A PSC motor could get direct line volt power from an aquastat, or an internal time delay relay.
A variable speed could get voltage on W1 and start the fan. Voltage at W2 will increase fan speed. 

The wiring you see where G is powered for fan in heat mode is usually done at the thermostat. There will be a "gas/electric" switch, or it will ask during installer setup "equipment or thermostat controls fan in heat mode".

That’s what I looking for , u the man