If I run 6/2 MC with ground from the panel inside a residence and strip the armor and pull the thhn through EMT for an EV charger without splicing it in the box where the cable exits the basement into the garage, is it necessary to bond the 4 square box where the transition takes place? There would be no splices in the Box. The MC would be attached using a listed fitting. And a set screw EMT connector is used.
Proper bonding for MC to EMT without splicing
- Thread starter tburke630
- Start date
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Yes, not only the MC armor but especially the box and EMT. You will have to pull some green back into the box and install a ground lug.
-Hal
-Hal
- Location
- New Jersey
- Occupation
- Journeyman Electrician
As Hal stated yes it's required. If you use MC-ap then you can skip the separate bonding jumper to the box.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
What if the EMT, and thus the box, were bonded to the EGC at the load end of the EMT?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Hmm I don't think that there is any wording in the NEC that directly addresses this. If the MC cable were PVC instead would the answer be the same? If the ungrounded condcutors are not spliced within the box then the connection to the EGC is not required however the box still needs to be grounded.
That's an option I've considered
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
My first thought was its just like the common situation using that exception where if there are no splices, then the EGC's can pass thru the box without connecting to the box or any other EGC's.....
- Location
- New Jersey
- Occupation
- Journeyman Electrician
But doesn't that only apply when the conductors are in a raceway or cable that qualified as an EGC? In this case the EMT on the "load side" of the box would be grounding the box.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I think I was thinking of 250.148. There isn't an exception, the rule is just "where circuit conductors are spliced within a box or terminate on equipment within or supported by a box...". I don't see any reason that wouldn't apply to the OP.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Perhaps what I said was confusing. Let me try this: I do not see anything requiring the OP to bond the EGC to the box, assuming the EMT is bonded at the load end by a metal enclosure or a bonding bushing.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
As I understand it, the scenario is...
MC Cable -> Listed Fitting -> Metal 4-square Box -> EMT -> Listed Fitting -> LFMC (less than 6') -> Listed Fitting -> Metal EV Charger Enclosure
If a ground fault happens anywhere along this path, where doesn't it make it back to the source? You can establish an effective ground fault current path either end of a conduit, regardless.
MC Cable -> Listed Fitting -> Metal 4-square Box -> EMT -> Listed Fitting -> LFMC (less than 6') -> Listed Fitting -> Metal EV Charger Enclosure
If a ground fault happens anywhere along this path, where doesn't it make it back to the source? You can establish an effective ground fault current path either end of a conduit, regardless.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
right. Sometimes you have to bond an EGC to a box even if it would otherwise still be properly bonded, but this is not one of those cases.
- Location
- Illinois
- Occupation
- retired electrician
Does the jacket of the MC qualify as an EGC? If it does, then no bonding is required. If not, then the EGC needs to be connected to the EMT at the load end.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The jacket is not an EGC in standard MC cable.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Almost, and in your scenario the LFMC would be an EGC, and the box and EMT would be bonded via wire-type EGC - metal enclosure - LFMC - EMT - box
But post #5 says "plastic enclosure connected via liquid-tite". Plastic enclosure puts the kabosh on that ground fault path, and liquid-tite could be LFMC or LFNC.
So it sounds like the box and the EMT are unbonded, and an additional measure is required to bond them. That could be bonding the wire type EGC to the box. Or if the liquid-tite is LFMC, it could be using a bonding bushing on the LFMC connector.
Cheers, Wayne