2023 NEC New Section 250.64(G)

[steve952]

New section 250.645(G) in the 2023 NEC States: "Grounding Electrode Conductors shall not be installed thru a ventilation opening of an enclosure." I understand the provision to prevent simply running a bare or insulated conductor thru the opening, but what about cutting a 7/8" hole and installing a fitting for an armored cable, would that be permissible?

On many projects we typically install a section of rebar (UFER) or a ground rod underneath the transformer and that UFER or Rod extends thru the bottom panel of the transformer and into the transformer enclosure. Would this be permitted?

The section doesn't say anything about ungrounded conductors, or equipment bonding conductors, or even grounded conductors passing thru the ventilation openings and I can't find another section in the NEC restricting those conductors from being installed thru the openings.

I assume this was to prevent the installation of bare or insulated conductors only and not to prohibit other raceways from entering the bottom of transformer enclosures. Keep in mind most floor mounted transformers don't have much room on the bottom that isn't ventilated, so this may complicate some installations.

 

[LarryFine]

Welcome to the forum.

New section 250.645(G) in the 2023 NEC States: "Grounding Electrode Conductors shall not be installed thru a ventilation opening of an enclosure." I understand the provision to prevent simply running a bare or insulated conductor thru the opening, but what about cutting a 7/8" hole and installing a fitting for an armored cable, would that be permissible?

Absolutely.

On many projects we typically install a section of rebar (UFER) or a ground rod underneath the transformer and that UFER or Rod extends thru the bottom panel of the transformer and into the transformer enclosure. Would this be permitted?

Yes, but you must still connect to the building's electrode system, too.

The section doesn't say anything about ungrounded conductors, or equipment bonding conductors, or even grounded conductors passing thru the ventilation openings and I can't find another section in the NEC restricting those conductors from being installed thru the openings.

Obviously a no-no. Ventilation opening area is probably why.

I assume this was to prevent the installation of bare or insulated conductors only and not to prohibit other raceways from entering the bottom of transformer enclosures. Keep in mind most floor mounted transformers don't have much room on the bottom that isn't ventilated, so this may complicate some installations.

You should always use or make knockouts and use fittings.

 

[letgomywago]

There are the small 3/8th KOs on panels that aren't for ventilation. You have to knock them out and those could be used also

 

[roger]

There are small openings in some enclosures specifically for GEC's that do not require any fitting

 

[letgomywago]

There are small openings in some enclosures specifically for GEC's that do not require any fitting

You can know their use since a nema 1 enclosure will not need a vent hole and a 3r usually has them in the bottom corners.

I think this code change is go try and force Kenny clamps on people by non understanding AHJs

 

[jaggedben]

What an unnecessary section.

 

[don_resqcapt19]

You can know their use since a nema 1 enclosure will not need a vent hole and a 3r usually has them in the bottom corners.

I think this code change is go try and force Kenny clamps on people by non understanding AHJs

A change to require that would have to say that the GEC must be secured to the enclosure. There is a PI for the 2026 code to require the GEC be secured to the enclosure, but that was resolved (rejected) at the Task Group meeting, but still has to be acted on when they have the CMP meetings in Jan. If it would get a 50% vote at the meetings, it would be balloted and would have to receive a 2/3s vote to become code. Won't know until the First Draft Report is published on July 10, 2024, but that is not the end as there are public comments, and second draft meetings, and possibly action on motions at the NFPA meeting in June of 2025.

 

[letgomywago]

A change to require that would have to say that the GEC must be secured to the enclosure. There is a PI for the 2026 code to require the GEC be secured to the enclosure, but that was resolved (rejected) at the Task Group meeting, but still has to be acted on when they have the CMP meetings in Jan. If it would get a 50% vote at the meetings, it would be balloted and would have to receive a 2/3s vote to become code. Won't know until the First Draft Report is published on July 10, 2024, but that is not the end as there are public comments, and second draft meetings, and possibly action on motions at the NFPA meeting in June of 2025.

Well anything to keep those out of the way I'm all for. It's not something that will stop electrical fires or shock potential.

 

[jim dungar]

There are the small 3/8th KOs on panels that aren't for ventilation. You have to knock them out and those could be used also

Wouldn't section be most applicable to ventilated transformers, where some contractors try to save by jamming the conductor through a factory slot? Very few disconnect switches, loadcenters or panelboards have factory installed ventilation openings, except for some 3R enclosures with drain holes.

I don't think the Kenny clamps ever caught on in this area.

 

[letgomywago]

Wouldn't section be most applicable to ventilated transformers, where some contractors try to save by jamming the conductor through a factory slot? Very few disconnect switches, loadcenters or panelboards have factory installed ventilation openings, except for some 3R enclosures with drain holes.

I don't think the Kenny clamps ever caught on in this area.

Transformer I've seen. Although I've never seen something I would think would overheat one.

Every time I hear someone think the keny clamps are code required I feel the need to push back on the idea.

 

[Fred B]

I don't think the Kenny clamps ever caught on in this area.

Never seen here. Does using one of these allow you to stop GEC at the clamp, and not carry it up to the already bonded Ground bus? Had cases that would be handy when the Ground bus didn't have openings large enough to land the 1/0 GEC.

 

[don_resqcapt19]

Never seen here. Does using one of these allow you to stop GEC at the clamp, and not carry it up to the already bonded Ground bus? Had cases that would be handy when the Ground bus didn't have openings large enough to land the 1/0 GEC.

No, the GEC still must land on the neutral bar at the service equipment.
The substantiation for the 2026 PI to require something like the Kenny clamp (not sure there is anything else) said the device would prevent the GEC from being pulled out of its termination and provide the required bonding between the enclosure and the GEC.

In my opinion, the GEC is not required to be bonded to the enclosure where it passes through the wall of the enclosure. The fact that it is bonded within the enclosure takes care of that issue.

I am sure it has happened, but I have never seen a case where the GEC has been pulled out of the termination within the enclosure, other then the cases where the service equipment has been completely ripped off the wall. I see no need too secure the GEC to the enclosure with any type of clamp.