250.140??

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360Youth

360Youth

Senior Member
Location
Newport, NC
I need some help with this one please. We are installing a generator and SE-rated ATS on a back to back residential service. The dryer is a 3-wire that crosses finished living area. Does this circuit need to be replaced new with 4-wire? Thanks. Replacing a circuit or two in instances like this can cost as much the entire generator installation.

250.140 Frames of Ranges and Clothes Dryers. Frames
of electric ranges, wall-mounted ovens, counter-mounted
cooking units, clothes dryers, and outlet or junction boxes
that are part of the circuit for these appliances shall be
in the
manner specified by 250.134 or 250.138.
Exception: For existing branch-circuit installations only
where an equipment grounding conductor is not present in
the outlet or junction box, the frames of electric ranges,
wall-mounted ovens, counter-mounted cooking units,
clothes dryers, and outlet or junction boxes that are part of
the circuit for these appliances shall be permitted to be
connected the grounded circuit conductor if all the following
conditions are met.
(1) The supply circuit is 1201240-volt, single-phase,
3-wire; or 208Y1120-volt derived from a 3-phase,
4-wire, wye-connected system.
(2) The grounded conductor is not smaller than 10 AWG
copper or 8 AWG aluminum.
(3) The grounded conductor is insulated, or the grounded
conductor is uninsulated and part ofa Type SE serviceentrance
cable and the branch circuit originates at the
service equipment.
(4) Grounding contacts of receptacles furnished as part of
the equipment are bonded to the equipment.
 
I believe you will find AHJ opinions will vary on this.
In the situation you describe, locally, if changing the 3 wire circuit is impractical, most will allow it to remain.
You will need to ask your AHJ, I believe.
 
augie47 said:
I believe you will find AHJ opinions will vary on this.
In the situation you describe, locally, if changing the 3 wire circuit is impractical, most will allow it to remain.
You will need to ask your AHJ, I believe.
Click to expand...

This particular AHJ is rather adamant about this code section. I am not sure why. IMO, this section is one of the greatest misconstruing of intent versus letter of the law.
 
Is your generator sized for the entire load ?
I ask only in that it might help justify the following:
Leave the existing service panel undisturbed with selected circuits remaining such as the dryer, (range ?), add feed thru lugs and feed your TS and new panel transferring most circuits to the new panel.
 
augie47 said:
Is your generator sized for the entire load ?
I ask only in that it might help justify the following:
Leave the existing service panel undisturbed with selected circuits remaining such as the dryer, (range ?), add feed thru lugs and feed your TS and new panel transferring most circuits to the new panel.
Click to expand...

Meter feeds ATS. ATS feeds house panel.
 
360Youth said:
Meter feeds ATS. ATS feeds house panel.
Click to expand...

If it is an ATS then the generator is supposed to be sized to handle the load it connects to, exception would be if load shedding practices are used to effectively lower the connected load.

Looks like I was posting at same time as Augie with basically same thoughts. Really has nothing to do with whether or not the 3 wire dryer circuit can remain 3 wire though.
 
Last edited:
augie47 said:
Too late for my plan "B" to work :D
Click to expand...

:)

He says if the circuit can be run back to the service, the 3-wire circuit can be left alone. I can do that by rerouting the dryer line to an outside disconnect, but I would have to tap the SE conductors ahead of the ATS main.

(3) The grounded conductor is insulated, or the grounded
conductor is uninsulated and part ofa Type SE serviceentrance
cable and the branch circuit originates at the
service equipment.
 
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