Furnace not working.

[Plumber69]

I installed a new transformer and board in a furnace. It still wouldn't power up. It has power and thermostat is jumpered. Then I realized I'm still not getting 24v out of the transformer. I tested more connections and the main power coming into the furnace(black has 120v and the white has 36v) would this cause transformer not to output 24v

 

[Reach4]

Blower door interlock switch?

 

[Sponsor]

 

[Plumber69]

Blower door interlock switch?

Even on the high powered side of the transformer black has 120v white has 36v.

 

[Plumber69]

Even on the high powered side of the transformer black has 120v white has 36v.

Door switch is fine

 

[Bgard]

Where are you testing the voltage to? Black to ground and white to ground? What do you have between black and white?

 

[Plumber69]

Where are you testing the voltage to? Black to ground and white to ground? What do you have between black and white?

I believe I had 80. Black to ground 120. White to ground 36

 

[Reach4]

I believe I had 80. Black to ground 120. White to ground 36

On the primary of the transformer? The white neutral wire should be near zero with respect to ground.

 

[Stuff]

So your white wire is disconnected somewhere. Trace it back to the breaker panel.

 

[Plumber69]

On the primary of the transformer? The white neutral wire should be near zero with respect to ground.

The white wire neutral has 36 volts. I don't see how this is even possible

 

[Stuff]

If a neutral is floating (not connected) at its source then it can be "powered" by devices on the circuit. In your case most likely the white wire is loose and is getting voltage through the furnace's transformer. If it was totally disconnected it would measure 120vac to ground and zero to the hot wire. Can you measure the white wire's voltage at the electrical panel?

The other thing that happens is phantom voltage. This is when a disconnected wire is in parallel with a powered ac wire. Through electromagnetism it picks up voltage. A digital meter is very sensitive so will pick this up. You will see recommendations to use an analog meter or a "Wiggy" to measure voltage.

 

[Plumber69]

I'm going to get an electrician there. There's 2 furnaces there. One works one doesn't. I test both electrical connections on both. The one that don't work I'm getting odd readings. I should of ran a extension cord from an outlet and hooked up the furnace

 

[Plumber69]

Update. Everything is working now. Originally there was no power to both furnaces. So I told them to get an electrican. Well he bypassed something and got power to both but messed up one of the connections. I assumed the electrician tested the power to the units. That's why I assumed it was the transformer or board.. there was a loose connection on the neutral well aways away