Shocking dryer revelation

[K8MHZ]

You have to wonder how the frame of the dryer was energized even with the reversed polarity. Was the cord pinched on the neutral at the connector? Was the neutral and ground bonded in the machine?

If the frame wasn't energized how did the customer keep getting shocked? If it was static then then without a ground there wouldn't have been a path to bleed off the static charge. Don's right the feet may have been insulated. Dryers do produce a lot of static electricty.

Good questions. It wasn't static because I measured 105 VAC.

I didn't check for a neutral to frame fault. I will the next time I am over there.

This occurred when the dryer was off. So, yeah, a pinched neutral seems like something to look for.

I should read open between the N - G conductors of the dryer cord, correct? Even with electronic controls?

 

[GoldDigger]

The GFCI can however, if designed for it, detect an unintended downstream connection between ground and neutral in the absence of leakage current by deliberately injecting a test signal.

Tapatalk!

 

[K8MHZ]

No GFCI that I am aware of has a reference to an equipment grounding conductor and none of them care what voltage is from either protected conductor to equipment ground. That is not what they are designed to do. They only monitor for balanced current between hot and neutral, or in the case of a 120/240 GFCI breaker they monitor for balance between all three load conductors. Anything that goes out one conductor has to come back on another protected conductor (within 4-6 mA max lost) or it will trip. Does not matter what is grounded, what is not grounded or if there is any ground period in the particular system it is connected to. You not only can have a trip from current of the protected circuit being lost, you can also have a trip if some foreign circuit somehow introduces current into the protected circuit - like mixing up protected and non protected neutral (or hot) conductors at a junction box into the same splicing device.

I believe that is a UL standard (for about 4-5 years now) and all GFCI receptacles will not reset if line and load are reversed. Thing is you can reset the device, then power it down, reverse the line and load conductors and it will continue to operate - until it is tripped- then it will not reset until line and load conductors are properly connected. They protect you when new because they leave the factory in a tripped state, but connect one that had been reset and this protection only kicks in once it has tripped.

Chances are the current was outside the protection that the GFCI can provide, like the incoming EGC was somehow connected to an ungrounded conductor somewhere, the GFCI will not monitor the EGC at all.

Even if the "shock" current was passing through a properly functioning GFCI it must be beyond the trip curve of the GFCI before it will trip. 5 mA may not trip it, but a person will definitely feel 5 mA and it will be more than a little tingle. If you want to play with this then plug a GFCI tester into a receptacle with a missing/malfunctioning EGC and a metallic WP cover or something similar that you will easily be touching while testing, and then press the test button on your testing device - unless you are well insulated it very likely will knock you on your behind.

They didn't hang onto it, I'm sure.

And I'll pass on intentionally shocking myself. Making such a suggestion seems a bit over the top to me, actually.

 

[mbrooke]

The GFCI can however, if designed for it, detect an unintended downstream connection between ground and neutral in the absence of leakage current by deliberately injecting a test signal.

Tapatalk!

Do all do so, is it just some or only specialty applications? I know most standard outlet GFCIs will trip on a neutral to ground fault under load. But Ive never caught one without load to see.

 

[GoldDigger]

I do not know the answer to that question. I have seen the circuit described, but I do not know whether it is required or common in either receptacle or breaker construction. It does not, however, require that a load be present, just the wired connection.
When the test voltage is induced by a transformer, it is possible to detect whether the current is flowing through a bond upstream or downstream of the tester.

Tapatalk!

 

[growler]

I didn't check for a neutral to frame fault. I will the next time I am over there.

This occurred when the dryer was off. So, yeah, a pinched neutral seems like something to look for.

I should read open between the N - G conductors of the dryer cord, correct? Even with electronic controls?

Yes, you should read an open between the neutral and ground on the dryer cord.

If you had ran a new circuit ( for good ground) and installed a new GFCI I think it would have tripped because of the neurtal to ground fault. As a matter of fact if there is a good ground in the kitchen you could just run an extension cord over and see if the kitchen GFCI trips.

 

[don_resqcapt19]

Levington makes a GFCI that will not reset if line and load are reversed or the internal GFCI circuitry is broken.

None of the GFCIs should work if the line and load are reversed. The GFCI must either trip and lockout, or give an audio or visual indication of failed electronics. These are both required by the July, 2006 revision to UL 943, the GFCI standard.

 

[don_resqcapt19]

I do not know the answer to that question. I have seen the circuit described, but I do not know whether it is required or common in either receptacle or breaker construction. It does not, however, require that a load be present, just the wired connection.
When the test voltage is induced by a transformer, it is possible to detect whether the current is flowing through a bond upstream or downstream of the tester.

Tapatalk!

I am not 100% sure, but I believe grounded neutral protection is required by UL 943.

 

[K8MHZ]

None of the GFCIs should work if the line and load are reversed. The GFCI must either trip and lockout, or give an audio or visual indication of failed electronics. These are both required by the July, 2006 revision to UL 943, the GFCI standard.

This would have a line only. No downstream receptacles.

 

[K8MHZ]

Yes, you should read an open between the neutral and ground on the dryer cord.

If you had ran a new circuit ( for good ground) and installed a new GFCI I think it would have tripped because of the neurtal to ground fault. As a matter of fact if there is a good ground in the kitchen you could just run an extension cord over and see if the kitchen GFCI trips.

We discussed running a new line to that addition. It may happen when the weather gets better. The room the dryer is in is also a bit of a mud room and people wet from the lake will be in there and we don't want them getting shocks.

 

[kwired]

How can the receptacle tell if the H -N is reversed if there is no grounding conductor?

It can't I was talking about reversed line and load connections.

They didn't hang onto it, I'm sure.

And I'll pass on intentionally shocking myself. Making such a suggestion seems a bit over the top to me, actually.

I guess you didn't detect the sarcasm that was intended to go with that statement, but it is a wake up that may just get a person to think about why they got knocked on their behind when they thought they were protected from such happening by a GFCI in the situation.

Do all do so, is it just some or only specialty applications? I know most standard outlet GFCIs will trip on a neutral to ground fault under load. But Ive never caught one without load to see.

I never seen one that did not trip immediately on a neutral to ground fault even with no connected load.

This would have a line only. No downstream receptacles.

cords plugged into the receptacle are the same thing as downstream receptacles - but you knew that. I'm pretty sure those plugged in loads are isolated from the feed thru load terminals when the device is tripped though, on the newer devices that protect from line -load reversal.