3 wire stove grounding

[Paul Allen]

So in a situation where there is a three conductor range and dryer circuit on the premises, and was fed off of a main breaker loadcenter.
New generator is installed with Service rated transfer switch, and four conductor wiring is installed from new switch to existing loadcenter.
Grounds and neutrals are separated, panel is now a feeder panel by definition. Circuit neutrals are terminated on the neutral buss, not grounding buss.
Problem, House is two story and three wire circuits cannot be accessed for replacement. Any code compliant way to be able to install this, or does the generator install or a potential service change get cancelled because owner doesn't want to tear out walls and ceilings to rewire.
What are everyone's thoughts on this? Would a code modification to allow 240 volt GFCI protection be a safe way to allow three wire circuits to be used when rewiring is not an option? let me know what you think.

 

[mbrooke]

If the neutral is insulated (3 wire without ground NM), it can indeed originate out of a subpanel.

 

[Paul Allen]

If the neutral is insulated (3 wire without ground NM), it can indeed originate out of a subpanel.

Agreed, but most of the time it is SE cable or NM with uninsulated ground conductor on installations I see frequently.

 

[kwired]

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.

For an existing circuit, if the uninsulated conductor originates in the service equipment exception allows you to not install a separate EGC anyway.

But at same time general rules are the grounded conductor must be insulated beyond the service disconnecting means, so you can't use the bare conductor for the grounded conductor here.

 

[kwired]

Agreed, but most of the time it is SE cable or NM with uninsulated ground conductor on installations I see frequently.

SE cable was and still is permitted if via the exception. NM was never permitted to use plain 3 wire in these instances unless the grounded conductor was insulated. Kind of didn't make sense but the way things were worded it had to be an SE cable if the grounded conductor was bare.

 

[kwired]

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

I think that may have been possible at one time. Has had to originate at service panel for some time now. Ssome inspectors may still let it go, or maybe don't really know the rules as written well enough themselves.

 

[kwired]

So in a situation where there is a three conductor range and dryer circuit on the premises, and was fed off of a main breaker loadcenter.
New generator is installed with Service rated transfer switch, and four conductor wiring is installed from new switch to existing loadcenter.
Grounds and neutrals are separated, panel is now a feeder panel by definition. Circuit neutrals are terminated on the neutral buss, not grounding buss.
Problem, House is two story and three wire circuits cannot be accessed for replacement. Any code compliant way to be able to install this, or does the generator install or a potential service change get cancelled because owner doesn't want to tear out walls and ceilings to rewire.
What are everyone's thoughts on this? Would a code modification to allow 240 volt GFCI protection be a safe way to allow three wire circuits to be used when rewiring is not an option? let me know what you think.

As code is written those must be changed to 4 wire circuits. I know there are some that get left, don't know the reasons, especially if inspected.

I guess you could install a separately derived system at/near the appliance,

 

[DBoone]

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

That’s the way I read it too.

 

[tortuga]

So in a situation where there is a three conductor range and dryer circuit on the premises, and was fed off of a main breaker loadcenter.
New generator is installed with Service rated transfer switch, and four conductor wiring is installed from new switch to existing loadcenter.
Grounds and neutrals are separated, panel is now a feeder panel by definition. Circuit neutrals are terminated on the neutral buss, not grounding buss.
Problem, House is two story and three wire circuits cannot be accessed for replacement. Any code compliant way to be able to install this, or does the generator install or a potential service change get cancelled because owner doesn't want to tear out walls and ceilings to rewire.
What are everyone's thoughts on this? Would a code modification to allow 240 volt GFCI protection be a safe way to allow three wire circuits to be used when rewiring is not an option? let me know what you think.

250.130(C) method is a very routine thing we do in panel changes where a meter/main is now added per 2020 code, id say almost weekly.
I realize Larry and others here see this differently but I believe the intent behind 250.130(C) is to safely ground non grounding outlets in such situations.
In my state per the law, an existing electrical installation only has to meet the code in effect at the time it was installed.
As I am not installing a new SE cable nothing about the existing SE cable is considered by our inspectors other than that bare is completely taped white. Even if I alter the outlet the SE cable is 'existing'. Just like the old 2 wire NM or BX that gets a #12 ECG tap.
We ground that 3 wire range outlet just the same way as you can ground any other non grounded two prong outlet as described in 250.130(C), I think that is way safer than leaving the 3 wire 10-50.

Typically when the electrician is running some #6 to the groundrods or even #4 to the water pipe he will hit the range box with a tail, or use a split bolt and run a tap.
Yes you sometimes run #6 thru cabinets, exposed around a house, but still better than replacing the whole circuit or using a neutral as an ECG.
Cheers

 

[mbrooke]

I think that may have been possible at one time. Has had to originate at service panel for some time now. Ssome inspectors may still let it go, or maybe don't really know the rules as written well enough themselves.

Even the code as written now lets you grandfather an insulated neutral out of a subpanel.

 

[kwired]

250.130(C) method is a very routine thing we do in panel changes where a meter/main is now added per 2020 code, id say almost weekly.
I realize Larry and others here see this differently but I believe the intent behind 250.130(C) is to safely ground non grounding outlets in such situations.
In my state per the law, an existing electrical installation only has to meet the code in effect at the time it was installed.
As I am not installing a new SE cable nothing about the existing SE cable is considered by our inspectors other than that bare is completely taped white. Even if I alter the outlet the SE cable is 'existing'. Just like the old 2 wire NM or BX that gets a #12 ECG tap.
We ground that 3 wire range outlet just the same way as you can ground any other non grounded two prong outlet as described in 250.130(C), I think that is way safer than leaving the 3 wire 10-50.

Typically when the electrician is running some #6 to the groundrods or even #4 to the water pipe he will hit the range box with a tail, or use a split bolt and run a tap.
Yes you sometimes run #6 thru cabinets, exposed around a house, but still better than replacing the whole circuit or using a neutral as an ECG.
Cheers

May be safer and your inspectors may allow it or even have an amendment that allows it, but I don't think taping the bare conductor of a SE cable is anything NEC recognizes as written. JMO.

 

[tortuga]

May be safer and your inspectors may allow it or even have an amendment that allows it, but I don't think taping the bare conductor of a SE cable is anything NEC recognizes as written. JMO.

Yeah there seem to bee good reasons to not use a neutral as an ECG out of a 'subpanel'.
There was this chief state inspector whom used to give a free CE class, it would draw a large audience, he told a story of a plumber and a old 3 wire range circuit.
I cant remember the details apparently the feeder panel that fed the range had lost its neutral from a meter pack.
The plumber made contact between the grounded dishwasher and the stove.
It ended badly, the story left me with the impression that outlets that use the neutral as an ECG are kinda like having a oil slick on the road.
Not a big deal if handeled correctly, but lots of opportunity for error.