Old sub panel landing 3 wire 240V branch for dryer

[Little Bill]

The explanation makes sense as to point of origin, but why type SE and not a 10/2 NM if both have an uninsulated ground?

The bare conductor (stranded) in SE cable was the grounded conductor. The bare conductor in NM cable is an EGC. The EGC was never allowed to be the grounded conductor. A bare grounded conductor was allowed to serve as the EGC but not the other way around.

 

[Fred B]

The bare conductor (stranded) in SE cable was the grounded conductor. The bare conductor in NM cable is an EGC. The EGC was never allowed to be the grounded conductor. A bare grounded conductor was allowed to serve as the EGC but not the other way around.

So even though it seems to have been a common practice that I've seen around here, it was never legal. It seems to be an interesting differentiation as both are bare copper, and if both originate in main panel, what makes one safer than the other? (Not arguing codes statement, but would like to understand reasoning if I'm going to enforce it to a GC, who would have seen the same thing that I've seen, and to a customer who might say "Its worked so far".)

 

[Little Bill]

So even though it seems to have been a common practice that I've seen around here, it was never legal. It seems to be an interesting differentiation as both are bare copper, and if both originate in main panel, what makes one safer than the other? (Not arguing codes statement, but would like to understand reasoning if I'm going to enforce it to a GC, who would have seen the same thing that I've seen, and to a customer who might say "Its worked so far".)

The EGC and grounded/neutral are always tied together in the main service equipment. However, the neutral carries current under normal circumstances but the EGC would only carry current under a fault condition. So you would/should not intentionally send current through the EGC. The bare conductor in NM is the EGC. In a subpanel, the grounds (EGC) and neutral are separated. That is why no bare grounded conductor, also acting as an EGC, can be run from a subpanel.

I suppose physically a 2-wire SE cable w/bare neutral and a 10-2 with bare EGC would work the same but is not legal. Maybe it is just the listing of SE cable with no EGC and 10-2 NM with no neutral I don't know. What I do know is that 10-2 with bare EGC was never allowed to be used as both an EGC and neutral. I also know it was done a million times. You can only tell a customer, or GC, that it's not allowed. Hard to explain the why not part.

 

[Fred B]

So I came across this one, someone had wired dryer using 10/2 NM and wrapped tape around the bare ground of the cable,( at the time I couldn't figure that one out). Your opinion, was this an attempt to circumvent the code requirement of either and insulated ground or type SE, or was it a legitimate means to meet code of an insulated ground?

 

[LarryFine]

In my opinion, no, taping the EGC does not qualify it as a circuit conductor.

 

[Fred B]

In my opinion, no, taping the EGC does not qualify it as a circuit conductor.

I tend to agree, just another head scratcher, what were they thinking.

 

[Little Bill]

I have been allowed to tape (white) the bare neutral of SE cable when the now main panel is changed to a subpanel. This might happen if a generator is installed with an ATS that is service rated. The ATS then becomes the main and the existing main is now the sub. Not saying it's legal but sometimes an inspector will use what I call "Andy Griffith" common sense. Taping it makes it a lot safer then it was when bare. This was allowed for me because it would have been a nightmare to run a 4-wire cable.

 

[LarryFine]

I have been allowed to tape (white) the bare neutral of SE cable when the now main panel is changed to a subpanel. This might happen if a generator is installed with an ATS that is service rated. The ATS then becomes the main and the existing main is now the sub. Not saying it's legal but sometimes an inspector will use what I call "Andy Griffith" common sense. Taping it makes it a lot safer then it was when bare. This was allowed for me because it would have been a nightmare to run a 4-wire cable.

Exactly the same for me once.

 

[curt swartz]

Old NM cable had a reduced EGC conductor so that may be why the bare conductor in NM cable was never permitted to be used in the the same way as the bare conductor in SE cable.

 

[garbo]

Just curious, working on a house that the range and dryer each only had 3-wire cables landing in a subpanel. The subpanel was wired with 4 conductors (as a subpanel in same building should be). Where would you have landed say the bare ground of the 10/2 NM of the dryer, on neutral or ground bus?
The existing wireing of the range and dryer landed differently, one of them on the neutral, the other on the ground. Based on the wire it could have been that way for more than 30 years.
Could have landing the wire on one vs the other caused or contributed to the breaker of the dryer becoming fused to the bus of the A side of Single-Phase? (Cant separate the breaker from the bus.) Found similar fusing on the 100 Amp main breaker of the same phase in sub panel (set screw welded). Heat damage on the 100A wire all the way back to main panel on that same phase.
Fyi, Panel is being replaced as well as feed wire back to main panel, upgrading range and dryer to 4 wire as part of a planned kitchen rewire and upgrade.

Cheap manufacturing companies were allowed to use the ground wire on electric dryers to not only ground the dryer but to feed the 120 volt dryer motor, drum light & control panel. If they were made to use 240 volts to supply everything this would not be a problem. Brought this up 50 years ago. In my area the 3 wire ststem is grandfathered in to existing servuce panel but hopefully not sub panels. Most AHU'S are great at taking time to answer your questions. They would like to go out just once to do any inspections.Only came across 1 prima donna inspector in my 50 years as a sparky.

 

[curt swartz]

Cheap manufacturing companies were allowed to use the ground wire on electric dryers to not only ground the dryer but to feed the 120 volt dryer motor, drum light & control panel. If they were made to use 240 volts to supply everything this would not be a problem. Brought this up 50 years ago. In my area the 3 wire ststem is grandfathered in to existing servuce panel but hopefully not sub panels. Most AHU'S are great at taking time to answer your questions. They would like to go out just once to do any inspections.Only came across 1 prima donna inspector in my 50 years as a sparky.

That is incorrect. The neutral (grounded conductor) was allowed to also be used as the equipment ground but the equipment ground was never allowed to be used as the neutral.

 

[LarryFine]

Cheap manufacturing companies were allowed to use the ground wire on electric dryers to not only ground the dryer but to feed the 120 volt dryer motor, drum light & control panel.

Not quite. It was an allowance to use the neutral (groundED) conductor to bond the cabinet.

 

[Eddie702]

3 conductor SE 1 conductor can be bare or 3 wire + a bare ground romex for stoves and dryers (in the past)

10/2 ok for electric water heaters 240 volt with no neutral current

 

[LarryFine]

3 conductor SE 1 conductor can be bare or 3 wire + a bare ground romex for stoves and dryers (in the past)

Actually, in the past, the insulated neutral could be used without a separate EGC.

In SE, the neutral can be bare; in NM, it must be insulated.