Found a panel with no bonding strap from the ground/nuetral bus to the panel enclosure. But the subpanel ground was bonded to the subpanel enclosure(with floating neutrals). The main and subpanel were next to each other and the metal bushing for the main and sub seemed to bond the two enclosures (hence the main is bonded to the sub). Does this mean the main panel is bonded to the ground system? Doesn’t seem right.
What is shown in photo #2?
that is the ground/neutral buses on the main panel
Square D panels usually have a green bonding screw inserted in the hole at the top of the neutral bar. Yours seems to be missing. Other than that the grounding looks OK.
thanks - just wasn’t sure. no green gournding screw found. that was part of the confusion.
Based on what I see, the service panel is not grounded properly.
There should be a bonding connection in picture #2 via (as Robert suggested) a green bonding screw attached through the grounding-terminal bar. It appears that the only “grounding” bond of the service equipment occurs through the conduit to the sub panel.
Am I missing something?
This is not fact so I caution any who read this.
Robert: You a sparky? The reason I am asking is from personal recall the size of the bonding screw should only fit that entrance. It can not be extracted and used on another portion of the board or panel.
just about to do a review on electrical and HVAC.
What do you mean it’s not fact?
I many examples of green bonding screws.
If you read the full post Michel it might give a better indication of the statement I was making to ***new members ***that might take my word as fact and apply it to there observation and reporting strategy.
This is not fact so I caution any who read this.
The reason I am asking is from " **personal recall ** which is not fact " the size of “the bonding screw should only fit that entrance”
The question for validity being “the bonding screw should only fit that entrance.”
Sorry if you misunderstood the statements intent or if I mistakenly did not express my self properly.
The very end should be the justifier but I could be wrong. “just about to do a review on **electrical **and HVAC.”
All the best.
I read the full post robbert.
I’m more confused than before Robert :roll:
Or at least one of us is.
I am also confused by this Robert.
I can tell you (for fact) that this panel is normally bonded with a machined screw, which is fastened through the open hole in the upper left of the terminal.
I can also tell you (for fact) that the screw provided by Square D will be green for this connection.
There are certainly other ways bonding can be achieved, but Robert M was correct in his statement about the bonding method.
Sorry if any members were confused.
All removed.
Thank you Michel and Jeff for pointing this out.
I should have reviewed my post after Michel pointed out there was discrepancy/s in my post verbiage.
Square D panels usually have a green bonding screw inserted in the hole at the top of the neutral bar. Yours seems to be missing. Other than that the grounding looks OK.
As to what I remember the bonding screw that is missing can only fit that size an opening.
Any help would be much appreciated.
Example of missing bonding screw shown:
http://www.nachi.org/bbsystem/viewtopic.php?t=17905&PHPSESSID=d07d5b40021da4aad425eb990c6191ba
Thanks Larry…
Still looking for the relation to size for the bonding screw.
It is in the forums somewhere.
I can’t confirm it but vaguely remember the bonding screw is one size and will not fit another thread on the panel.
Yes thanks Larry.
Here’s a electrical inspection check list.
Based on the 2011 NEC® and the 2009 IRC
I did not go over it yet. To busy with my 2012 ICC code book. Just arrived yesterday.
The bonding screw is provided by the panel manufacturer and should be tested to ensure that it’s properly sized to carry the fault current. IMO they’re not interchangeable from one brand to another.
Thanks Robert.
The referencing I am looking for is “any bonding screw” (green foe SD) should not fit in any threaded opening on that spastic panel.
I have not heard they are not interchangeable on other panels also.
Dam where’s that reference.
I will find it.
Don’t forget that the screw length is also critical. The wrong screw that’s too long may hit the surface behind it and not be tightly or fully seated against the neutral bus. I would guess that if you dig around you can find a reference stating that the manufacturer requires their specific, proved screw be used for this task otherwise a properly sized wire jumper needs to be used.