Square-D panels and bonding

Originally Posted By: ddivito
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Whenever I see one of these panels used as the main service panel, I never find a bonding strip. I do not find a screw from the neutral/ground bus bar making contact either.


How can I determine if there is bonding by using a tester?


Originally Posted By: Brian A. Goodman
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Dennis,


It sounds like you mean bonding the enclosure to the neutral bar. If so, you can check it by using the ohm / continuity mode of a meter. Touch one lead to the neutral bar and the other to the enclosure and you should get continuity. You may need to find a bare spot on the enclosure, like the inside edge of a screwhole or KO. Be careful in there.


Originally Posted By: cbuell
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Dennis,


Sometimes on Square D the bonding screw isn’t green and its semi-hidden behind the Neutral service wire.


Originally Posted By: ddivito
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Brian A. Goodman wrote:
Dennis,
you can check it by using the ohm / continuity mode of a meter. Touch one lead to the neutral bar and the other to the enclosure and you should get continuity. You may need to find a bare spot on the enclosure, like the inside edge of a screwhole or KO. Be careful in there.


If a pigtail continuity tester placed between a live line and the enclosure "glowed" wouldn't that indicate that the bonding was present? I would visually make sure no bare grounding wires were touching the enclosure.


Originally Posted By: Greg Fretwell
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You should really try to verify the bonding is done in the panel. Incidental connections can trick a tester but still allow objectionable currents to flow. You may be seeing a path through the plumbing or even the TV or PC back through the telco/cableco equipment. A real fault or a lightning strike could cause more damage than neceessary and that questionable path might not even clear the fault.


Originally Posted By: jpope
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Greg Fretwell wrote:
Incidental connections can trick a tester but still allow objectionable currents to flow. You may be seeing a path through the plumbing or even the TV or PC back through the telco/cableco equipment.


Perfect point Greg. That's exactly why home inspectors should NOT try and determine these things.

It's simple - The panel bond was not visible at the service panel. Further evaluation by a state-licensed electrical contractor is recommended to determine if the panel is properly bonded..


--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738

Originally Posted By: ddivito
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Here is a reply I received from Square-D today


"As far as I know there is no tester that will check for this because the neutral could be
bonded before the main service.
On our equipment you can check the wiring diagram for the location where the bonding should be
done and if a screw is used it must a green color."

Gary Shireman
Manager Product Support
Square D/Schneider Electric

Your response seems right on Jeff.


Originally Posted By: Brian A. Goodman
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[quote=“jpope”]


That's exactly why home inspectors should NOT try and determine these things.

It's simple - The panel bond was not visible at the service panel. Further evaluation by a state-licensed electrical contractor is recommended to determine if the panel is properly bonded..

Ah come'on Jeff, you're spoiling our fun. We wanna get in there with the ole' meter, do a little poking & proding. ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)


Originally Posted By: bbadger
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cbuell wrote:
Dennis,
Sometimes on Square D the bonding screw isn't green and its semi-hidden behind the Neutral service wire.


If it is not green you are either looking at the wrong screw or the wrong screw has been used.

Quote:
250.28 Main Bonding Jumper.(B) Construction. Where a main bonding jumper is a screw only, the screw shall be identified with a green finish that shall be visible with the screw installed.



--
Bob Badger
Electrical Construction & Maintenance
Moderator at ECN

Originally Posted By: jtedesco
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On the other hand, the main bonding jumper may be the same color as the other screws in the neutral terminal bar because the panelboard might have been installed before the new rule was added.


I remember when an Electrical Inspector from Portland Oregon proposed the green color back in 1990, because he also found it difficult to find that screw too. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

Can we see a close up picture!

Also, if the label on the equipment indicates: "Suitable for use as service equipment only" then the neutral will be factory bonded to the cabinet.

Look at the label to find out if that is true. If the word "only' is missing that that means that the panelboard can be used at the service when the MBJ is installed, or as a subpanel when it is not installed. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm