Trough bonding

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SamsTLC

Member
Location
Ocean county, NJ
Occupation
Electrical Contractor
I am in the middle of installing a large trough system for tenant space meters and need some help with figuring out the bonding (and EGC) for the whole system.

Case is - No meter stacks permitted by local utility for 480V services. Opting for a main disconnect with a trough that will feed individual meters, Fused disconnect, and into individual tenant spaces. The attached diagram should explain it all.
I am using PVC as the conduit between the trough and the main. The conduit between trough and meter, and between meter and disconnect are all threaded galvanized nipples. I will be tapping the mains load side with insulated bugs to each meter socket with the appropriate size wire (#1 Alu for the 100A, and 4/0 Alu for the 200A).
My thinking is, I land my UFER ground and my main water bond at the 600A disconnect. From the bonded neutral kit within the main Dissconect, I run a #1cu to a terminal lug in the trough.
My question is, Do I need to run a bonding jumper from my Feeder disconnects to the trough or can I rely on the metal enclosures as an effective bond?
Any other comments or glaring errors that you would like to spring at me are greatly appreciated :)

Thanks
Sam 1691633454588.png
 

tom baker

First Chief Moderator & NEC Expert
Staff member
Location
Bremerton, Washington
Occupation
Master Electrician
Trough is not a code term. Is it a wireway or auxiliary gutter? Once we know what it is we look in the appropriate article for bonding rules
 
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tom baker

First Chief Moderator & NEC Expert
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Location
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Master Electrician
One more question are the tenant spaces dwelling or non dwelling units? If on dwelling why 4/0 aluminum for 200 amp
 

SamsTLC

Member
Location
Ocean county, NJ
Occupation
Electrical Contractor
I would say that these are Auxilaruy gutters since the intention is to give more space for wire which would not fit in the main service panel.

These are non-dwelling units (480V Warehouse space) 4/0 is adequate per the unit's load calc.
 

don_resqcapt19

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Location
Illinois
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retired electrician
I would say that these are Auxilaruy gutters since the intention is to give more space for wire which would not fit in the main service panel.

These are non-dwelling units (480V Warehouse space) 4/0 is adequate per the unit's load calc.
If the item in question is connected to other enclosures using nipples, it is a wireway and not an auxiliary gutter. An auxiliary gutter has a large opening into the enclosure it is auxiliary too, so that the actual space in the original enclosure is increased. Auxiliary gutters are fairly rare.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Since you have a service disconnect. Would these not be feeder taps.
With a feeder and using a meter enclosure watch out for netural bonding in the meter and using RMC nipples.

Check with your AHJ for allowed method if using utility meter with netural bonding in meter enclosure.

You may have to use PVC and run an insulated EGC from unit disconnect into wire way and pass thru meter enclosure.

This may be allowed if meter enclosure is not attached to a metal rack shared by the rest of the equipment or mounter to. Metal building shell.

If your using meter enclosures that do have a netural bond.
RMC would be fine.

As far as bonding wire way, run a proper sized EGC from the service disc and bond to wire way. Size it off of the OCPD of the service disc.

You would not be required to run a wire type EGC to wire way from unit disconnect as long as you follow NEC rules and the equipment is listed for grounding and bonding over 250v.

If these are feeder taps and you have 200 amp fuses in you unit disconnects a 4/0 Al would be a violation under the tap rule.
The tap conductor would need to be sized to the 200 amp. Your wire type EGC if used to wire way from unit disc would need to be sized off of the 600 amp disconnect fuse size.

Then watch your tap conductor size to the 100 amp unit disc.

These are not service conductors once you have a service disconnect (main).
 

SamsTLC

Member
Location
Ocean county, NJ
Occupation
Electrical Contractor
Since you have a service disconnect. Would these not be feeder taps.
With a feeder and using a meter enclosure watch out for netural bonding in the meter and using RMC nipples.

Check with your AHJ for allowed method if using utility meter with netural bonding in meter enclosure.

You may have to use PVC and run an insulated EGC from unit disconnect into wire way and pass thru meter enclosure.

This may be allowed if meter enclosure is not attached to a metal rack shared by the rest of the equipment or mounter to. Metal building shell.

If your using meter enclosures that do have a netural bond.
RMC would be fine.

As far as bonding wire way, run a proper sized EGC from the service disc and bond to wire way. Size it off of the OCPD of the service disc.

You would not be required to run a wire type EGC to wire way from unit disconnect as long as you follow NEC rules and the equipment is listed for grounding and bonding over 250v.

If these are feeder taps and you have 200 amp fuses in you unit disconnects a 4/0 Al would be a violation under the tap rule.
The tap conductor would need to be sized to the 200 amp. Your wire type EGC if used to wire way from unit disc would need to be sized off of the 600 amp disconnect fuse size.

Then watch your tap conductor size to the 100 amp unit disc.

These are not service conductors once you have a service disconnect (main).
Thanks for the thorough write up!

Regarding the meters neutral bond - these meters do have a bonded neutral so I will be good..

Good point on the sizing of the feeders for 200A. They are indeed just that, feeders. And as such will nneed to be sized fully. 3/0 Cu it'll be.

My only remaining question is, don't I need to run a bonding jumper to each conduit entering the trough to ensure proper ground path throughout the system?
These conduits are not entering through concentric knockouts, they are entering through a clean 2.5" hole for the 2.5" gal nipple.

Thanks!
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Thanks for the thorough write up!

Regarding the meters neutral bond - these meters do have a bonded neutral so I will be good..

Good point on the sizing of the feeders for 200A. They are indeed just that, feeders. And as such will nneed to be sized fully. 3/0 Cu it'll be.

My only remaining question is, don't I need to run a bonding jumper to each conduit entering the trough to ensure proper ground path throughout the system?
These conduits are not entering through concentric knockouts, they are entering through a clean 2.5" hole for the 2.5" gal nipple.

Thanks!
First I would address the meter.
Netural bonding in the meter on a feeder is not desirable. The meter enclosure is allowed to be bonded thru the netural however a parrelle path on the feeder EGC is established. The way around this is to isolate the meter enclosure from the feeder EGC.

This is why I mentioned talk with AHJ on accepted practice for a netural bonded meter enclosure on a feeder.

Then address bonding. You do not want the EGC running to the wire way from the service disconnect to carry current in normal operating conditions. Which will be in parrelle with the netural and a code violation if you use ridged nipples between the meter and wireway.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Since you have a service disconnect. Would these not be feeder taps.
With a feeder and using a meter enclosure watch out for netural bonding in the meter and using RMC nipples.

Check with your AHJ for allowed method if using utility meter with netural bonding in meter enclosure.

You may have to use PVC and run an insulated EGC from unit disconnect into wire way and pass thru meter enclosure.

....
Exception #2 to 250.142(B) permits the neutral to be bonded to the meter for this application without any restriction on the wiring method between the meter and service disconnect.

Every service in our town has that current path as all of the meter cans acceptable to the utility have bonded neutrals and our local code only permits RMC or IMC as wiring methods for service conductors.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
agree with don (Post #10).. we see those installs often and the exception he references is applied.
An appropriately sized EGC from MDP to the wireway will cover that bonding and, assuming the nipples to the meter sockets enter hubs on the socket that would bond the nipples.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Exception #2 to 250.142(B) permits the neutral to be bonded to the meter for this application without any restriction on the wiring method between the meter and service disconnect.

Every service in our town has that current path as all of the meter cans acceptable to the utility have bonded neutrals and our local code only permits RMC or IMC as wiring methods for service conductors.
I went and read the section.
You are correct and I apologize for the mistake. Thank you for correcting me.

SamsTLC
Sorry for supplying incorrect information on the meter.
Your drawing complies with the exception.

Would ten push up get me off the hook?
 

SamsTLC

Member
Location
Ocean county, NJ
Occupation
Electrical Contractor
So, Spoke with AHJ today.

He quoted the same exception to 250.142(B) and therefore was Ok with the whole installation.
The only thing he asked me to add was a bonding bushing to each RMC nipple entering the Trough from the meter (cough... wireway), and install a bonding jumper sized to the 200A OCD.
I am still not sure why I would need it since the RMC is threaded to the hub on one end and into a non-concentric knockout on the other.

Thanks all for your advice!
 

SamsTLC

Member
Location
Ocean county, NJ
Occupation
Electrical Contractor
I went and read the section.
You are correct and I apologize for the mistake. Thank you for correcting me.

SamsTLC
Sorry for supplying incorrect information on the meter.
Your drawing complies with the exception.

Would ten push up get me off the hook?
Hey, retracting your info is more than enough! Wish that would happen on its forum more often. would be less confusing advice all around.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Good news
Thanks for letting me off the hook.
Glad the correct Info was given.
Tried to do ten only could do two. Getting old, two a day be done in five.
 
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