Article 250.142(b)

[Randylee]

4/23/19
Job info:
Residential
240 volt, Single phase

I recently did a service upgrade on a house and it failed inspection.
The inspector discussed his reason for failing the job. He referenced 250.142 b



The home had an old 100 amp service with an interior breaker panel with a 100 amp main breaker fed by a 3 conductor cable (common thing).

I removed the old meter and installed a 200 amp weatherproof panel with anMain breaker. Leaving the inside panel untouched I used the existing 3 conductor cable and connected to a 100 amp breaker in the new outside panel.

The inspector is referring to code 250.142 B as for him failing the job.
He’s explaining to me since I installed the new panel outside and turning the inside panel a sub then I must replace the 3 conductor with a 4 conductor and separate the grounds and neutrals.

I read 250.142 B
For system NOT having a main disconnecting means.


I have a 200 amp main in the outdoor panel, a 100 amp in the outdoor panel protecting the old 3 conductor feeding the old indoor panel which has a 100 amp breaker protecting that panel.
So the disconnects are there.




How do you understand this?
Should my job Pass or Fail?
Thanks Randy

 

[augie47]

The job should fail !
You can also use reference 250.24(A)(5)


(That said I have seen situations where the AHJ would allow the 3 wire to stay when it was impractical to replace it, but the Code does require the 4 wire)

 

[Randylee]

Thanks for replying.

I understand the 4wire if installing a new sub panel but it’s an existing panel.
First time I had one fail for this.

 

[LarryFine]

He’s explaining to me since I installed the new panel outside and turning the inside panel a sub then I must replace the 3 conductor with a 4 conductor and separate the grounds and neutrals.

That's exactly correct. The main disconnect is, or becomes, the last place in the service entrance that the neutral is bonded to grounded surfaces and GECs, and marks the beginning of the premises EGC system.

The same applies when adding a service-rated transfer switch to an existing service, and even to existing 3-wire major appliance circuits; they're supposed to be converted to 4-wire circuits, receptacles, and cords.

 

[LarryFine]

I understand the 4wire if installing a new sub panel but it’s an existing panel.
First time I had one fail for this.

That allowance applies to existing feeders to separate structures, and then only if there are no other metallic pathways, such as water or gas piping, between them.

 

[jaggedben]

It's an existing panel but you changed its function from service equipment to sub. The inspector is right. I hope you can easily replace the feeder cable, because the various exceptions to running the EGC with the circuit conductors do not apply to feeders.

 

[LarryFine]

One more technicality: #2 al SER is not large enough for a 100a-breaker-protected sub-panel feeder. So, if he's a stickler (I don't believe his ruling on the existing feeder makes him one), you might want to ask before you buy and install (and then, you might not).


Added: I would not be shy of explaining this to the customer and asking for (maybe discounted (maybe labor and materials, but no mark-up)), the cost for the additional work required.

 

[LarryFine]

The same applies . . . to existing 3-wire major appliance circuits; they're supposed to be converted to 4-wire circuits, receptacles, and cords.

Unless they're re-routed to be supplied by the panel containing the new main disconnect.



(It's not often one has occasion to quote oneself. )