3 Wire, 4 Wire Code

[curt swartz]

The other end Green/Yellow wire is connected to the back side of the neutral terminal. It is the factory installed bonding jumper. If you leave it connected with a 4-wire installation you have created a hazardous condition especially if the receptacle is being fed from a feeder. The EGC will now be a parallel path for all neutral current on the feeder. As KB and Steve point out this wire needs to be removed from the frame and either connected back to the neutral terminal or insulated. I recommend not cutting the wire off incase the dryer gets moved to different location that only has a 3-wire receptacle.

 

[Power Tech]

As an SE cable, yes; as NM cable, no. An SE cable bare can be used as a neutral; an NM cable bare cannot be.

Remember, this was a case of the neutral being able to do double duty as the EGC, not the other way around.

I thought it was a 2 wire with ground. On the old dryer receptacle, the 3rd wire is a neutral?

 

[Power Tech]

Went back and installed a 10/4 so and 4 wire receptacle & plug.

Pulled a neutral from the panel.

The HO was understanding. I only charged him parts for my mistake.

Thanks for all the replies.

 

[benaround]

Went back and installed a 10/4 so and 4 wire receptacle & plug.

Pulled a neutral from the panel.

The HO was understanding. I only charged him parts for my mistake.

Thanks for all the replies.

Thanks for doing the right thing !!

 

[hurk27]

I thought it was a 2 wire with ground. On the old dryer receptacle, the 3rd wire is a neutral?

Yep it has always had to be full sized, and it has always been required to be run from the service panel where the MBJ is, never from a sub panel.

 

[LarryFine]

I thought it was a 2 wire with ground. On the old dryer receptacle, the 3rd wire is a neutral?

Absolutely. The heating element is the only thing connected to L2. Everything else (drum and timer motors, lights) is wired L1 to N.

That's why they can be used on either 120/240v or 120/208v (albeit with 75% heating capacity on 208v compared to 240v).

An electric water heater, on the other hand, is line-to-line (240v or 208v) only.

 

[LarryFine]

Yep it has always had to be full sized, and it has always been required to be run from the service panel where the MBJ is, never from a sub panel.

. . . if you were using a 3-wire feed; a 4-wire always could originate in other than the main panel.

 

[kbsparky]

For those who claim that I was wrong in removing and isolating that green/yellow wire, I say to you prove it! I will not accept opinions only.

Here is the proof I offer that it was done correctly:

I checked with the owner's manual for the appliance. In it, they identify that green/yellow jumper as the neutral grounding wire. It is used only for 3-wire circuits, and provides the grounding of the frame through the neutral conductor. The instructions actually call for the wire to be removed from the green screw, and reattached to the neutral terminal.

I taped it up instead. (so shoot me). :grin:

The other method of proof lies in a simple continuity test. Try unplugging your dryer, and put your continuity tester across the neutral and grounding prongs. YOU SHOULD NOT GET ANY CONTINUITY on a properly connected 4-conductor cord.

IF that green/yellow wire is connected to the frame of the appliance you will fail the continuity test. Disconnect the jumper and test again.

Report back here with your proof.

 

[curt swartz]

Anyone here that disagrees with KB, Steve or me please read pages 7-9 from this PDF.
http://www.whirlpool.com/assets/pdfs/product/ZINSTALL/WED5590VQ_Installation Instruction.pdf

 

[K8MHZ]

On both 4 wire connections the 'neutral ground wire' is removed from the chassis and re-connected to the neutral terminal on the terminal strip. I don't see why, but it is Whirlpool's instructions. If that wire is green, or green with a trace, I REALLY fail to see why it would be connected to the neutral.

Nothing is mentioned about leaving it disconnected.

I may be looking at the PDF wrong. I had to print it out to read it and still had a hard time figuring out where the wires in the illustrations were terminated. Maybe I am mistaken that the green wire is to be connected to the neutral terminal?

 

[kbsparky]

No you are not mistaken. That green wire is the neutral grounding wire. They tell you to attach it to the neutral, since that is where it originated from, and they don't want any loose bare wire ends floating about.

Manufacturers have begun using the wire pigtail as a bonding jumper in lieu of the older bonding strap these days. The problem arises when someone had a 4-wire cord installed, and then later moves the appliance to a new premises which only has a 3-wire outlet available.

Permanently removing the bonding strap leads to such appliances being reconnected with a 3-wire cord, and then operating without any bonding or grounding connection.

Just today, I was asked by a customer to install a new dryer outlet, since they recently moved into a new house which only had a gas dryer connection available. The dryer is several years old, with a 3-wire cord attached.

I installed a 4-wire circuit and NEMA 14-30R receptacle as required. I also changed the cord to match. While in this process, I noticed some potential hazards, so I took some photos to document what I found. The date/time stamps are accurate.

You can call the first photo "Before" -- this is how I found the appliance. No connector, and screw missing from access panel cover.

The 2nd photo is "before" with access cover removed. Notice that one of the hot wires has begun to melt, due to a loose connection. Also note that the bonding strap is missing.

3rd photo shows the new cord installed, with all connections tight.

Last photo shows the instructions on how to install a 3-wire cord on this appliance. It is a sticker on the back of the dryer.

Now the question comes to mind: What if they had moved into a house with a 3-wire outlet? They would never had called for an electrician, and simply plugged in their defectively wired dryer and went on with life.

That is until the loose connection melted the cord sufficiently to short out the hot line to the frame of the appliance. But, with the bonding jumper missing, a definite shock hazard would have manifested itself between the grounded washer adjacent, and the electrically hot frame of the dryer sitting next to it.

How would the lady of the house been able to deal with being zapped while transferring wet laundry from the washer to the dryer under such a scenario?