Sub Panel with no EGC

[PowerdT]

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Does the enclosure of the new panel have concentric or eccentric knockouts that you will be using? If it does, are those knockouts "listed to provide a reliable bonding connection"? (250.97)

Panel is not ordered yet. I will make sure contractor comply with 250.97.

 

[tom baker]

The calculations will say that the EMT is an effective ground fault path for a longer distance than a wire type EGC that has been sized per Table 250.122.

Search for the steel tube institute GEMI software program

 

[Dennis Alwon]

The reason I mentioned is because I have seen some panels in commercials building with no EGC feeder, but they have green wire bonded to the EMT knockout then to ground busbar inside panel

I wonder if you are seeing service entrance conductors that have a bonding jumper from the Emt to the ground or neutral in the panel.

 

[PowerdT]

I wonder if you are seeing service entrance conductors that have a bonding jumper from the Emt to the ground or neutral in the panel.

This is sub panel, it’s not service entrance panel . On my particular case, for the existing sub panel, feeder comes in EMT raceway to the sub panel no bonding jumper from EMT to ground bus.

 

[Ponchik]

As mentioned earlier EMT is allowed as an EGC. You can mount your own grounding buss in the panel and your future conductor type EGC can go the the buss bar.

 

[Ponchik]

FWIW,

From the 2015-2016 UL white book.


CONCENTRIC OR ECCENTRIC KNOCKOUTS

All boxes with concentric or eccentric knockouts have been investigated for bonding and are suitable for bonding without any additional bonding means around concentric (or eccentric) knockouts where used in circuits above or below 250 V, and may be marked as such.

 

[infinity]

FWIW,

From the 2015-2016 UL white book.

That doesn't apply to a cabinet with a panelboard in it.

 

[Dennis Alwon]

This is sub panel, it’s not service entrance panel . On my particular case, for the existing sub panel, feeder comes in EMT raceway to the sub panel no bonding jumper from EMT to ground bus.

I was referencing where you said you have seen some panels with a ground from the conduit to the panel

PowerdT said:
The reason I mentioned is because I have seen some panels in commercials building with no EGC feeder, but they have green wire bonded to the EMT knockout then to ground busbar inside panel

 

[PowerdT]

I was referencing where you said you have seen some panels with a ground from the conduit to the panel

I see yes there is bonding jumper from EMT knockout to ground bus inside sup panel

 

[Ponchik]

That doesn't apply to a cabinet with a panelboard in it.

I agree, hence FWIW.

From Scheider Electric:​

Are the concentric knockouts in the load centers, metering, or safety switches rated for grounding (or bonding) in accordance with the NEC, using a standard nipple or… | Schneider Electric USA

Are the concentric knockouts in the load centers, metering, or safety switches rated for grounding (or bonding) in accordance with the NEC, using a standard nipple or connector?​

Issue:
Product Design Features

Product Line:
Load Centers, Safety Switches and Metering

Resolution:
No. There is no test in the UL standards for these product lines for the knockouts of the enclosures. The test for this requirement is found in UL 514A (Standard for Safety - Metallic Outlet Boxes) only. The enclosures for load centers, metering, and safety switches are manufactured to the UL 50 standard. The installer MUST use a "Bonding Bushing" for such a connection or follow what the code requires.

Published for:Schneider Electric USA​

Published on:5/18/2005Last Modified on:3/1/2022

​

 

[electrofelon]

The OP did say this is a 480V panel. I have never seen a panelboard cabinet with KO's, FWIW.