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A blog by Son of Samurai in General

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How Does this Dryer Run in a Seemingly Impossible Configuration?

Son of Samurai

Entry posted by Son of Samurai

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Imagine you're out on a call, and you run into this:

Screen Shot 2020-11-05 at 10.51.57 PM.png

As the picture says, the dryer runs like this. And even weirder, when you correct the wiring, it stops running.

Take a minute to think, then see if you can answer this pop quiz:

1. How does the dryer run in this configuration?

2. What's wrong about the wiring in this configuration?

3. Why does it stop working when you correct the wiring?

4. What one test could you do that would prove your hypothesis about this faulty circuit?

When you think you've got your answers, watch the webinar I've linked below. In it, we go in depth on how this circuit works so that you can understand it inside and out. We'll talk about the schematic, the underlying electrical principles, and how you can be prepared so that you're not fooled by situations like this in the field.

This webinar recording is available only to premium members at Appliantology -- click here to become one today.

 

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MVrepairs

MVrepairs

Posted

Great post.

 

WOOKIE

WOOKIE

Posted

Very Scary .

1. It is using the chassis ground wire as a return path to the circuit breaker panel.

2. In this configuration if the ground to the house is interrupted then , if the unit were to short,  the chassis become hot and could electrocute anyone touching the unit completing a path to ground

3. It would stop if the white wire is not connected to the neutral bar allowing a return path.

4.It could be tested by  connecting white wire to the middle connector and removing the black wire from the ground to the middle connector and see if the unit works.  If it does not run , reconnect the black wire to the middle connector along with the white wire from the cord.  If it run's it confirms that the white wire does not have a return path. 

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Samurai Appliance Repair Man

Samurai Appliance Repair Man

Posted

  • Team Samurai
42 minutes ago, WOOKIE said:

1. It is using the chassis ground wire as a return path to the circuit breaker panel.

2. In this configuration if the ground to the house is interrupted then , if the unit were to short,  the chassis become hot and could electrocute anyone touching the unit completing a path to ground

 

Right on.

42 minutes ago, WOOKIE said:

3. It would stop if the white wire is not connected to the neutral bar allowing a return path.

In a 4-wire configuration, Neutral and Ground are separated at the dryer and only bonded at the circuit breaker box. Notice the black jumper wire from ground to the Neutral lug-- this is removed for a 4-wire configuration. That's a clue as to why the dryer runs when the wiring is corrected. See the webinar for details.

44 minutes ago, WOOKIE said:

4.It could be tested by  connecting white wire to the middle connector and removing the black wire from the ground to the middle connector and see if the unit works.  If it does not run , reconnect the black wire to the middle connector along with the white wire from the cord.  If it run's it confirms that the white wire does not have a return path. 

There's an even easier test that doesn't require removing or attaching any wires-- just your meter. The webinar walks through all this. 

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WOOKIE

WOOKIE

Posted

(MAMDA) Yes, I forgot about the most basic diagnostic tool . Disconnect the black wire then, check for continuity between the green and white wires.

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Samurai Appliance Repair Man

Samurai Appliance Repair Man

Posted

  • Team Samurai
1 hour ago, WOOKIE said:

check for continuity between the green and white wires.

In this case, you would be checking for continuity from Neutral, back to the circuit breaker box (where Neutral and Ground are bonded) and then back to the ground wire at the dryer. But remember that something can check "good" on ohms but still be "bad" because it fails (goes open) under load. Ohms testing is a screening test: if something tests open, it's bad, you found the problem. But if something tests "good" on ohms, it may still be bad. That's why we don't rely on "good" ohms tests for diagnostic conclusions. 

Ohms checking is fine for DIYers who don't know anything about circuits because it's safe. But professional techs should rely on volts and amps for diagnostic conclusions. 

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RKH

RKH

Posted

This is the type of error that results in electrocution. While it will function, if the the Neutral/Ground bond at the main panel became loose (or ground rod connection) an electrical failure in the dryer could cause the entire ground circuit of the home to become energized. A death trap.

I had a convenience store where the entire 'beer cave' was energized due to a shorted condenser motor. The condenser was not grounded properly. A lady touched the handle while also touching a grounded coffee dispenser. She was knocked out cold. Luckily, her hand fell away from the handle. Ambulance was called. She was okay. 

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WOOKIE

WOOKIE

Posted

 I believe it, I had a condenser fan motor that would run and , if you touched the water heater  while the condenser fan motor was running you received a pretty impressive shock . It all goes back to improper grounding.    You have to be extremely careful in older houses that have been renovated.  I.E.  installing a water line to a refrigerator under a pier and beam house.   We had a plumber here Electrocuted years ago when he grabbed a gas line under the house. The range was shorting to ground and the house   Circuit panel was not properly grounded. 

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