Thermostat voltage and resistor value
#1
Member
Thread Starter
Thermostat voltage and resistor value
Hello all,
I have a few questions regarding the testing the thermostat.
When the thermostat cover is removed, the voltage between Y and R should be ~24V AC , the voltage between Y and C should be 0, and there should be continuity between Y and R.
Q1> Since there is a continuity between Y and R, but the Y has no voltage, so it is true that there is a large resistor between the Y and R?
Q2> When the thermostat cover is installed back and the unit calls for cooling, the Voltage between R and Y should be 0 and Y and C should be ~24V AC. Is that correct?
Is it true that somehow the thermostat shorts the Y and C when it calls for cooling?
Q3>Unrelated question.
When I measure the wall outlet, the voltage between hot and neutral is 120V. The voltage between the hot and the ground is 120V while hot has no continuity to ground.
When I measure the voltage between R and myself. Why there is no voltage?
Why not 24V?
Thank you
I have a few questions regarding the testing the thermostat.
When the thermostat cover is removed, the voltage between Y and R should be ~24V AC , the voltage between Y and C should be 0, and there should be continuity between Y and R.
Q1> Since there is a continuity between Y and R, but the Y has no voltage, so it is true that there is a large resistor between the Y and R?
Q2> When the thermostat cover is installed back and the unit calls for cooling, the Voltage between R and Y should be 0 and Y and C should be ~24V AC. Is that correct?
Is it true that somehow the thermostat shorts the Y and C when it calls for cooling?
Q3>Unrelated question.
When I measure the wall outlet, the voltage between hot and neutral is 120V. The voltage between the hot and the ground is 120V while hot has no continuity to ground.
When I measure the voltage between R and myself. Why there is no voltage?
Why not 24V?
Thank you
#2
Member
with cover removed there should not be continuity between Y and R. Normally Y goes to the contactor in the outside unit which also has a connection to C to activate its coil.
Thermostat connects Y (and usually G) to R with a cooling call.
Measuring between R and you (or to most anything else) is meaningless. Sometimes will get voltage if C is connected to ground at the HVAC unit but that is not always the case. Same issue when birds sit on a high voltage line and don't get fried..
Thermostat connects Y (and usually G) to R with a cooling call.
Measuring between R and you (or to most anything else) is meaningless. Sometimes will get voltage if C is connected to ground at the HVAC unit but that is not always the case. Same issue when birds sit on a high voltage line and don't get fried..
#3
while hot has no continuity to ground.
Continuity (ohms) should never be measured in a powered circuit.