Dryer cord - 3-wire vs. 4-wire

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JerryR

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A couple of questions. I never understood the logic of 3-wire dryer cords where there was a ground strap to neutral jumper on the dryer side.

1- Is there improved safety upgrading a dryer cord from 3-wire to 4-wire?

2- What's the risk if someone didn't remove the jumper or ground strap from neutral to ground at the dryer lugs, when installing 4-wire from a previously 3-wired connection?
 
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hj

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1. As a practical matter, not much
2. There is no "risk" if you have the neutral and ground bonded together with a 4 wire cord, but why wouldn't you remove it.
3. In most cases, with a three wire setup, the ground is attached to the neutral and has to be relocated to the ground lug when you convert to four wire.
 

DonL

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Why would you be upgrading a dryer cord from 3-wire to 4-wire, when you only have 3 wires feeding it ?


Did I miss something ?
 
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Jadnashua

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IF you have a ground at the junction box where the plug to your dryer is, you should put in a 4-wire plug and pigtail. You are only grandfathered if the supply run does not have a ground. So, if the thing is being inspected, it should fail if you have a ground, but chose not to use it by buying a new 4-wire cord (and maybe receptacle). The ground should never be carrying current, but if there is a fault, it is safer if it is there...keep in mind that neutral WILL be carrying current if there is any part of the dryer running on 120vac (most of the time, there is, but not always). The ground should not be carrying current except in a fault condition.
 

JerryR

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Why would you be upgrading a dryer cord from 3-wire to 4-wire, when you only have 3 wires feeding it ?


Did I miss something ?

Don,

The reason is I'm married and I'm a wimp. I was very happy the way things were.

We sold one of our 3 homes in January and we're getting ready to sell another now so wife is having me do musical appliances.

Wife wanted dryer from house we sold in January installed in the 1996 constructed house we bought last year. This house already had a 3-wire dryer/receptical installed. The dryer we took from the home we sold in January had a 4-wire pigtail. It was easy to just replace wall receptical with spare 4- wire, NEMA 14-30R and my thoughts were it may be safer with separate ground. The box already had grnd + neutral + 2 hots. I have several NEMA 14-30R's on hand from my job before I retired.

Last week, after 10 months, I was finally able to convince my wife to allow me to donate 2 dryers and 1 washer to Habitat for Humanity. My wife wanted to keep them as spares just in case. Did I mention I'm a wimp?
 

DonL

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Sounds like you did good.

The nice thing about having a Ground is that if the heating element was to short to ground you have better protection.

Maybe your wife will let you plug in now. Sounds like you may have made her happy.


Have Fun.
 

ActionDave

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1- Is there improved safety upgrading a dryer cord from 3-wire to 4-wire?
Yes. The extra safety from an equipment ground has been required since the 1960's it just took a while for the old farts in the NEC to get around to re-writing the one small section in the code that did not require one for dryers. Even when three wire circuits were allowed there were specific restrictions that applied to them.

2- What's the risk if someone didn't remove the jumper or ground strap from neutral to ground at the dryer lugs, when installing 4-wire from a previously 3-wired connection?
The risk is putting electrical current on all the conductive paths in common with the dryer circuit. Sure it is current at ground potential but, anything going awry with any of those paths can move that current and the voltage that drives it above ground potential; same thing as breaking the neutral wires of a circuit and putting one hand on each of them.
 
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