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Isolated ground buss in sub panel #51449
04/29/05 02:22 PM
04/29/05 02:22 PM
D
drwindows  Offline OP
Junior Member
Joined: Apr 2005
Posts: 1
I am in the process of installing a main lug sub panel off the meter main.

The meter main has the neutral & ground buss bars bonded, and the new sub panel has them isolated. I've also removed the swing arm that bonds the neutral buss to the backplane as per code.

Here is the problem....this sub panel from CutlerHammer not only has the neutral buss bar up on plastic risers, but the ground buss bar is also up on risers.

This creates a condition where there is no continuity from the sheet metal of the panel to either the neutral buss or the ground buss.

If there is a short to the panel and the panel becomes "hot", some one touching the sheet metal would become the path to ground.

How can this be right???

Why do the isolate the ground buss from the sheet metal by raising it up on plastic risers just like the neutral buss???

Work Gear for Electricians and the Trades
Re: Isolated ground buss in sub panel #51450
04/29/05 02:34 PM
04/29/05 02:34 PM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 6,919
Brick, NJ USA
Welcome to ECN.
IF the 'meter/main' is the first means of disconnect, the neutral has to be tied into the ground at that point. A insulated neutral, bare or insulated ground, and your phase conductors (hots) go from the "main" to the sub-panel.

At the sub-panel, the neutral terminal block has to be insulated from the enclosure, hence the plastic insulation. The ground bar has to be mechanically 'bonded' to the panel enclosure. This is usually accomplished via a bond screw into a tapped hole, a bond strap, or any other suitable means.

The mfg instructions provide a list of approved 'parts' that may have to be purchased separatley to provide a SAFE and code compliant installation.

From your wording, you need to purchase a CH ground bar at the supply house. The insulated 'neutral' bars are for neutral conductors only within a sub-panel.

John


John
Re: Isolated ground buss in sub panel #51451
04/29/05 02:43 PM
04/29/05 02:43 PM
E
earlydean  Offline
Member
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
Are the two busses electricaly connected together? If not (or they can be separated), put that swing arm back in and viola, you have a ground buss.


Earl
Re: Isolated ground buss in sub panel #51452
04/29/05 03:00 PM
04/29/05 03:00 PM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Generally when I use a panel like this once the connecting bar is removed I use the bonding screw sent by the manufacturer to bond one of the terminal bars to the enclosure.

This bonded bar becomes the grounding terminal bar.

Some panels (GE for one) allow the installer to choose either bar.

This bonding screw or strap was shipped with your panel.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

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