What is everyones take on this? We are constantly arguing about putting bond bushings on transformers (SDS not Services). These 45, 75, 112 KVA and up are not services but everyone wants to slap bond bushing everywhere and they keep calling them "New Services" in the buildings...why? Drives me nuts! Also putting bond bushings on Greenfeild...? Flex is only rated for 20 amps as a ECG, so whats the point of putting a bond bushing on for fault current when its not even rated/listed for it....especially at transformers....better off putting a bond bushing on PVC IMO...:lol:
Bonding of SDS and FLEX
- Thread starter Canton
- Start date
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masterinbama
Senior Member
- Location
- Huntsville Alabama
I very rarely use bonding bushings on anything other that RGS stub ups in switchgear.
I use bonding lock nuts on service conduits and make every effort to flush PVC bell ends with the slab under gear to save the expense there too.
I use bonding lock nuts on service conduits and make every effort to flush PVC bell ends with the slab under gear to save the expense there too.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I see and argue about the same thing all of the time. I know of no requirement to put a bonding bushing on FMC at a transformer for the reason you've mentioned. If the KO were concentric or eccentric then maybe we would have a different discussion.
I agree. With the limtation on flex as a equipment grouding conductor, a bonding bushing, IMO, would be useless.
As Infinity notes, in a hard piped system with concentric or eccentric knocknouts there is the possibiloity of the need.
As Infinity notes, in a hard piped system with concentric or eccentric knocknouts there is the possibiloity of the need.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Regarding bonding and grounding, I usually think of larger FMC as if it were PVC. Also it's still is required to be grounded since it metal but that accomplished by the FMC connector itself.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Like infinity said, the metal flex must still be bonded, but can only be used as an equipment grounding conductor with specific conditions, involving length, and maximum overcurrent protection. Most of the installations mentioned in the OP will be beyoned the limits and the flex only needs to be bonded, not treated like it is an EGC. Concentric/eccentric KO's may effect how this is accomplished.
kbsparky
Senior Member
- Location
- Delmarva, USA
We recently installed some new equipment for an emergency power supply system in an existing building. New panels -- both 480 Volts, and 208Y/120, transformers, transfer switches, etc.
They had some bonding bushings there for my use, but since I had cut all my knockouts into blank wireways and enclosures I did not feel they were needed. No concentric or eccentric knockouts were encountered or used. I used plastic bushings instead.
All the lines we installed included equipment bonding conductors, so we did not rely on any flex for grounding purposes.
They had some bonding bushings there for my use, but since I had cut all my knockouts into blank wireways and enclosures I did not feel they were needed. No concentric or eccentric knockouts were encountered or used. I used plastic bushings instead.
All the lines we installed included equipment bonding conductors, so we did not rely on any flex for grounding purposes.
- Status