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Pop Quiz: What's Wrong with this Range Wiring?


Son of Samurai

3,581 views

You open up the terminal block on a Bosch range, and you see this. What's wrong with this picture? (Hint: those of you who have watched this webinar recording should know what's up).

F524C5F7-4218-4DB1-922C-46703B7EF3EE.jpeg.21b1c169ac1a24e133f6da97fb2caaad.jpeg

A few questions for you sharp Appliantology techs:

  1. Will the machine run in this configuration?
  2. Why is it not okay to leave the machine in this configuration?
  3. Does this machine have a 3 or 4 wire power cord?
  4. How would you correct this situation?

Let me know your answers in the comments below!

Are you stumped, or do you want to learn more about this kind of misconfiguration and the problems it could cause? Watch the webinar recording below where we covered a very similar situation -- available only to premium members of Appliantology.

Dryer_Cord_Wiring_Weirdness_-_Professional_Appliantologist_Webinars_Forum_-_Appliantology_org_-_A_Master_Samurai_Tech_Appliance_Repair_Dojo.png

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11 Comments


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tcmeyer14

Posted (edited)

  1. Will the machine run in this configuration? NO 
  2. Why is it not okay to leave the machine in this configuration? Safety not properly grounded.
  3. Does this machine have a 3 or 4 wire pigtail cord? Neither it is hard wired using a 3 wire w/ground
  4. How would you correct this situation? Remove the jumper from neutral on terminal block to ground and put the capped white wire in the neutral terminal of the block. 
Edited by tcmeyer14
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  1. Will the machine run in this configuration? Yes
  2. Why is it not okay to leave the machine in this configuration? In this configuration the ground would be the current carrying wire. Big no no
  3. Does this machine have a 3 or 4 wire power cord? 4 wire cord
  4. How would you correct this situation? Remove the green wire completely. Attach the white neutral wire from cord to neutral lug on terminal block. 
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  • Team Samurai
Son of Samurai

Posted

@tcmeyer14, you've mostly got it -- but for question #1, the machine would actually run. Ground is bonded to neutral at the breaker box, so this is technically a complete circuit.

But ground is carrying current in this configuration, since it's acting as the return for the 120 VAC circuits in the range. Ground is never supposed to be a current-carrying conductor. Its sole purpose is to act as a safety.

@rbair, you're spot on with every question!

For those curious, this is what the corrected terminal block looks like:

225A4355-5191-4FE4-B479-B127EB7AD02C.jpeg.5e37239e9a1c8c93db0e1cc9b62286e9.jpeg

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Son of Samurai, Thank you for the correction. I some times run into a situation where the range or dryer has the 4 wire power cord correctly wired but still wont work. I find that the outlet itself has the ground and neutral reversed.

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  1. Will the machine run in this configuration? yes
  2. Why is it not okay to leave the machine in this configuration? safety hazard
  3. Does this machine have a 3 or 4 wire power cord? 4
  4. How would you correct this situation? white to center block and remove green wire.
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In this configuration, wouldn't you get shocked if you touched the metal frame of the range?

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  • Team Samurai
Son of Samurai

Posted

27 minutes ago, vallen513 said:

In this configuration, wouldn't you get shocked if you touched the metal frame of the range?

Good question! The answer is no, unless there is a break somewhere in ground, either in the power cord or in the house wiring. And if that's the case, then the range wouldn't run at all, since it would have no 120 VAC return.

In order for a person to get shocked by an appliance, there needs to be a voltage difference between the chassis and another surface that they are touching (say, the floor or a piece of metal plumbing). In our case, there's no voltage standing on the chassis because the machine is still grounded.

This video demonstrates this concept very clearly. As the Samurai shows here, you can grab hold of neutral with dozens of amps of current flowing through it, but since neutral is at ground voltage potential, you don't feel a thing. It's all about the voltage difference between two points.

 

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Myappliancefixed

Posted

On 12/12/2020 at 9:55 AM, Son of Samurai said:

@tcmeyer14, you've mostly got it -- but for question #1, the machine would actually run. Ground is bonded to neutral at the breaker box, so this is technically a complete circuit.

But ground is carrying current in this configuration, since it's acting as the return for the 120 VAC circuits in the range. Ground is never supposed to be a current-carrying conductor. Its sole purpose is to act as a safety.

@rbair, you're spot on with every question!

For those curious, this is what the corrected terminal block looks like:

225A4355-5191-4FE4-B479-B127EB7AD02C.jpeg.5e37239e9a1c8c93db0e1cc9b62286e9.jpeg

Green wire threw me off looks like it was connected from the factory. What if I would not remove the green wire an connect the white one to the same terminal. Would you get electricuted from touching the stove because a return wire is connected to the body of the stove? 

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  • Team Samurai
Son of Samurai

Posted

14 minutes ago, Myappliancefixed said:

Green wire threw me off looks like it was connected from the factory. What if I would not remove the green wire an connect the white one to the same terminal. Would you get electricuted from touching the stove because a return wire is connected to the body of the stove? 

Nope, it wouldn't cause someone to get electrocuted, for the same reasons I gave in my previous comment in response to vallen513. However, if you left that jumper there, you would invalidate the entire purpose of having a 4 wire cord.

The 4 wire cord is a safety improvement over the 3 wire cord, since it keeps ground and neutral separate. With a 4 wire, even if neutral goes open, the machine is still properly grounded. Not so with a 3 wire cord, and not so with this configuration if you correct the neutral but leave the ground jumper.

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Samurai Appliance Repair Man

Posted

Just to add... another reason the NEC is requiring 4-wire configurations is for the situation where the Neutral goes open and Line contacted the chassis as in a shorted load like a motor. In a 3-wire configuration, when Neutral goes open, so does Ground and the chassis is now at Line potential wrt to another grounded surface (kitchen tap, refrigerator, floor, etc). In a 4-wire configuration in this same situation— open Neutral— the breaker will trip as soon as Line touches the grounded chassis because of the independent Ground conductor. 

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I find at least 90% of 4-wire ranges and dryers miswired. The most common mistake is not removing the neutral jumper from the chassis. I've run into a few dryers with 3-wire cords and open neutrals. The complaint is dryer not working and getting shocked when touched. The 4-wire cords are much safer. That wire looks to be too small for a range. If it's 10 gauge, the circuit breaker should be no larger than 30 amp. 

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