3 wire stove grounding

[ROMERT M]

A older house has a 3 wire cable (two hots and a ground/neutral) from a range going to a sub fed panel. Does the ground/neutral wire terminate on the neutral buss or the grounding buss? Personally I think it goes to the neutral buss because it has 120v neutral current from timer and other 120v portions of stove. Comments?

 

[hbiss]

Yeah, it goes to the neutral bus. The 3 wire connection uses the neutral for a jackleg ground.

-Hal

 

[LarryFine]

Welcome to the forum.

Your installation is non-compliant as it is. A 3-wire major appliance circuit was compliant only when fed from the service panel, not a sub-panel. If fed from a sub-panel, it should have always been a 4-wire circuit, just like the sub-panel itself should be.

The best answer in this case is to carefully tape it (white) and land it on the neutral; otherwise, the sub-panel feeder's EGC would be subject to neutral current.

The old 3-wire circuit allowed the neutral to also serve as the equipment ground, not the other way around.

 

[texie]

Welcome to the forum.

Your installation is non-compliant as it is. A 3-wire major appliance circuit was compliant only when fed from the service panel, not a sub-panel. If fed from a sub-panel, it should have always been a 4-wire circuit, just like the sub-panel itself should be.

The best answer in this case is to carefully tape it (white) and land it on the neutral; otherwise, the sub-panel feeder's EGC would be subject to neutral current.

The old 3-wire circuit allowed the neutral to also serve as the equipment ground, not the other way around.

This seems to be wildly misunderstood. There are a lot of 3 wire ranges and dryers out there connected to other than service panels that were never compliant.

 

[rnatalie]

It should never have gone to the equipment grounding bus (other than they being the same at the service equipment). The exception reads "the frames... shall be permitted to be connected to the grounded circuit conductor."

The "originates at the service equipment" is in the clause covers the use of ungrounded conductors in SE cables. If you have an insulated grounded conductor, it can run to a subpanel (and should land on the neutral bus rather than the equipment ground bus).

 

[tortuga]

Ill just add you have some easy options to make it complainat with out rewiring, you can put some white tape on the bare SE neutral and run a #10 ECG to any accessible point on the grounding electrode and convert it to a 4 wire.

 

[rnatalie]

Where in the code does it say you can remark a bare wire and use it for something other than an equipment ground.

 

[tortuga]

Where in the code does it say you can remark a bare wire and use it for something other than an equipment ground.

338.10(B)(2) Exception:
In existing installations, uninsulated conductors
shall be permitted as a grounded conductor in accordance with
250.32 and 250.140, where the uninsulated grounded conductor
of the cable originates in service equipment, and with 225.30
through 225.40.

 

[rnatalie]

I should have been less terse in my answer. First, it says nothing about remarking. Second, that exception is only allowed when there is no EGC present, but your suggestion provides one.

 

[tortuga]

I should have been less terse in my answer. First, it says nothing about remarking. Second, that exception is only allowed when there is no EGC present, but your suggestion provides one.

I am not remarking and ECG as a neutral in new work, were talking old work pre 1996.
We are not discussing making a new electrical installation at all other than the #10 ECG,
Receptacle replacement does not trigger the entire branch circuit to need to be brought up to code, Changing a (non grounding) NEMA 10-50 to a 14-50 is just changing a device like any other.
The SE cable is an existing installation, feeding a non grounded outlet, prior to 1996 it was permitted to use a bare neutral for a branch circuit in such cable, so your not remarking anything, your marking it.


250.130(C):

 Nongrounding Receptacle Replacement or Branch
Circuit Extensions. The equipment grounding conductor of a
grounding-type receptacle or a branch-circuit extension shall be
permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system
as described in 250.50

 

[rnatalie]

Again, it's not legal according to the NC in my opinion. You're not taking about leaving the circuit as it is or just replacing the receptacle.
You're adding an EGC which while it sounds like a great idea makes the excemption for using the bare wire in the SE cable for the grounded conductor no longer apply. Putting tape on it doesn't change things and that in itself is ILLEGAL under the code even when you are using the exception (you can quibble over the difference between remark and mark, but it makes no difference to the discussion).

 

[tortuga]

Again, it's not legal according to the NC in my opinion. You're not taking about leaving the circuit as it is or just replacing the receptacle.
You're adding an EGC which while it sounds like a great idea makes the excemption for using the bare wire in the SE cable for the grounded conductor no longer apply. Putting tape on it doesn't change things and that in itself is ILLEGAL under the code even when you are using the exception (you can quibble over the difference between remark and mark, but it makes no difference to the discussion).

Rnatalie The situation I use this on and get it passed by inspectors comes up often here, it goes like this,
Lots of older homes around here have a 'banjo' meter on the outside of the house, and a decent run of unfused conductors to an older panel in say a laundry room.
When we do a service change/upgrade a meter main is used on the outside of the house, due to the original panel being some distance inside the house, a new SER cable is run to the original panel location.
Now the grounds and neutrals are separated, and the code exception that allows the range and dryer to be grounded by the neutral is lost.
So inspectors here will allow the method I suggested in that situation, as they cant allow the NEMA 10-50's to remain.

 

[LarryFine]

Now the grounds and neutrals are separated, and the code exception that allows the range and dryer to be grounded by the neutral is lost.

The solution is to replace the 3-wire circuit with a 4-wire. You were given a treat by being allowed to do what you did.

I was allowed to leave a 3-wire circuit when I showed the inspector that it would have been impossible to run a 4-wire from the garage to the house, because of the construction. I white-taped the bare SE conductor and landed it on the neutral bus.

 

[tnugent25]

Gentlemen,
This thread is very interesting, thanks for all the comments. I have, what I think is the same situation.
A "modern" house built around 1996? My friend is replacing the (E) Range with a brand new one. The cable feeding it(hardwired) is a 3 wire-2 hots and an Aluminum bare Neutral. I'm told it goes back to the subpanel which is on the outside of the house as a flush Meter Main with Distribution.
I'm assuming that the distribution/sub panel will have separate grounds and neutrals by code? The CB is 2p 50A, I will verify the
(E) wire size.
We will be adding an 50A 4 wire outlet and 40A? 4 wire Range cord("it fits"?). Waiting on verifying the Nameplate rating.
What I've gathered from your comments is:
1. Phase bare neutral white.
2. Connect bare neutral, in distribution panel, to the neutral buss.
3. Run a "#10 ECG to any accessible point on the grounding electrode and convert it to a 4 wire. "
The house has a concrete slab?, cabinetry, an abandoned PVC conduit in the slab- going somewhere? etc.
What are some options for finding that grounding point? Can I take it to a nearby receptacle/switch box and attach it to the ground wires in that box?
Any other suggestions?

Thanks! Tom
California

 

[shortcircuit2]

[QUOTE="tnugent25, post: 2624302, member: 85512"
I'm told it goes back to the subpanel which is on the outside of the house as a flush Meter Main with Distribution.
I'm assuming that the distribution/sub panel will have separate grounds and neutrals by code?
[/QUOTE]


Tom...this arrangement would be service equipment with grounds and neutrals together and 3-wire range line is permitted to stay per the exception in 250.140

 

[LarryFine]

Agreed. And, if you keep the 3-wire circuit, you should use a 3-wire cord and receptacle, and install the range's bonding strap.

 

[tortuga]

Gentlemen,
3. Run a "#10 ECG to any accessible point on the grounding electrode and convert it to a 4 wire. "
The house has a concrete slab?, cabinetry, an abandoned PVC conduit in the slab- going somewhere? etc.
What are some options for finding that grounding point? Can I take it to a nearby receptacle/switch box and attach it to the ground wires in that box?

If you went the 4 wire route you would need to take it back to the service or the grounding electrode system, you cant attach in a switchbox.
In cases like this we run a #8 bare or a #6 bare.

 

[mbrooke]

Welcome to the forum.

Your installation is non-compliant as it is. A 3-wire major appliance circuit was compliant only when fed from the service panel, not a sub-panel. If fed from a sub-panel, it should have always been a 4-wire circuit, just like the sub-panel itself should be.

The best answer in this case is to carefully tape it (white) and land it on the neutral; otherwise, the sub-panel feeder's EGC would be subject to neutral current.

The old 3-wire circuit allowed the neutral to also serve as the equipment ground, not the other way around.

Not true, if the neutral was insulated it could come from a sub-panel.

 

[don_resqcapt19]

Not true, if the neutral was insulated it could come from a sub-panel.

This provision has always applied only where the branch circuit originated at the service equipment.

(2020 NEC) 250.140 Exception ...
The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment. ...

(1978 NEC) 250-60 ...
(c) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a a service-entrance cable and the branch circuit originates at the service equipment ...

 

[mbrooke]

This provision has always applied only where the branch circuit originated at the service equipment.

Ummm... "The grounded conductor is insulated"