SSBJ sized using 250.102(c)(1)

[ctaylo360860]

I have a single phase 240/120 400 amp supply coming from poco transformer to my tap box. They ran 3-500mcm copper supply conductors. I plan to tap off the supply conductors to two 200 amp single phase panels using 3/0 copper conductors.
I’m looking at exhibit 250.12 and want to make sure I’m sizing my bonding jumpers and correctly Installing my gec.

The tap box needs to have a supply-side bonding jumper. Poco supplied 500mcm copper from transformer, and I have two sets of 3-3/0 copper conductors.
Should I size my Ssbj based on the poco conductors or my largest service conductors?
If it’s poco I need to run 1/0 cu from grounded conductor tap to the lug on my tap box.
If based on 3/0 being the largest I should be able to run #4 copper.
The picture in exhibit 250.12 shows the gec going to the tap box neutral.
Is that the only way, or Can I run #6 cu from each service disconnect out to two ground rods at each building? The buildings don’t have metal water pipe or ufer.

Also looks like I need to use 10ft ground rods since they will be going inside of the concrete sidewalk?

 

[Dennis Alwon]

I almost asked this question a while back so you can read it for yourself. It appears that you would size it to the 2- 3/0 conductors

grounding electrode conductor

Based on this thread https://forums.mikeholt.com/threads/gas-and-water-pipe-bonding.2575283/#post-2848700 it got me thinking. If I were to be responsible for the service lateral to the meter base and I sized it for voltage drop (500kcm conductors) and then used my standard size (4/0...

forums.mikeholt.com

 

[jaggedben]

Depending on where the service point is you would size off either the 500 MCM conductors or the combined cross section of the (2) 3/0 and the answer is 1/0 either way. It's the same for your GEC, if you're landing here, unless it's just going to rods..

10ft ground rods are not required anywhere by the NEC.

 

[jaggedben]

I guess if you are saying that because of the sidewalk an 8ft ground rod can't be put into the soil a full 8ft then yes, a 10ft ground rod could solve that.

 

[jaggedben]

So looks like I need to run #6 from each service disconnect to- 2 ground rods at least six feet apart, and I can use a #4 as my ssbj from grounded conductor to the enclosure?

Yes. If you're also putting the GEC here, maybe replace that 4-port polaris with a 5-port one so that you can connect the SSBJ and GEC both directly to the grounded conductor.

 

[ctaylo360860]

I guess if you are saying that because of the sidewalk an 8ft ground rod can't be put into the soil a full 8ft then yes, a 10ft ground rod could solve that.

Okay so I need a 1/0 ssbj from grounded conductor tsp to enclosure to make sure my enclosure is bonded.

 

[ctaylo360860]

I guess if you are saying that because of the sidewalk an 8ft ground rod can't be put into the soil a full 8ft then yes, a 10ft ground rod could solve that.

Yeah I got 2-10 foot ground rods for that reason

 

[ctaylo360860]

Yes. If you're also putting the GEC here, maybe replace that 4-port polaris with a 5-port one so that you can connect the SSBJ and GEC both directly to the grounded conductor.

I thought about this, and this maybe the way to go… i need to get project going and supply house took forever last time I ordered Insulated taps.
Is it a problem to run the gec from each service disconnect.
Basically the metal tap box is bonded to the grounded conductor via 1/0 ssbj enclosure lug and tap lug.
Both service conductors should be bonded via green screw in enclosure

Each service disconnect will have its own #6 gec and two ground rods

 

[ctaylo360860]

I thought about this, and this maybe the way to go… i need to get project going and supply house took forever last time I ordered Insulated taps.
Is it a problem to run the gec from each service disconnect.
Basically the metal tap box is bonded to the grounded conductor via 1/0 ssbj enclosure lug and tap lug.
Both service conductors should be bonded via green screw in enclosure

Each service disconnect will have its own #6 gec and two ground rods

Something like this at each buildings service disconnect.

 

[jaggedben]

Yes, you can run separate GECs from each panel. For example, they could meet at the first rod, and then one could continue as bonding jumper to the second rod.

No undeground water pipe in this building?

 

[augie47]

I see no problem with what you plan.
(You do need your bond screw in each panel)

 

[ctaylo360860]

Yes, you can run separate GECs from each panel. For example, they could meet at the first rod, and then one could continue as bonding jumper to the second rod.

No undeground water pipe in this building?

So I had planned on running two separate gecs from each service to two sets of ground separate ground rods. The picture I posted is an example at one of the services…

 

[jaggedben]

They should share the ground rods. Always one grounding electrode system per structure.

 

[ctaylo360860]

I see no problem with what you plan.
(You do need your bond screw in each panel)

Yeah tap enclosure should be bonded via 1/0 copper from grounded lug to lug on tap enclosure,both service panels are bonded via green screw and have a gec to grounds rods rom each service.

 

[ctaylo360860]

They should share the ground rods. Always one grounding electrode system per structure.

They’re two different buildings… something like this…

 

[ctaylo360860]

Thank you for all the speedy replies you guys are awesome!

 

[jaggedben]

Ok if there's only one connection to the poco it's still one service. But since you have service panels on each building then yes, separate GECs and electrodes at each building, going to each service panel. All kosher.

 

[ctaylo360860]

Thank you for the in depth and speedy replies truly appreciate you! Best way would have been to 5 port it and only pound one set of ground rods! After getting these 10 footers I may go that route if I can get them quick.
Meant from each service disconnect. Can’t edit my post now

 

[ctaylo360860]

Yes, you can run separate GECs from each panel. For example, they could meet at the first rod, and then one could continue as bonding jumper to the second rod.

No undeground water pipe in this building?

They ran plastic inside the building

 

[jaggedben]

Doesn't matter what they ran inside the building (although you're supposed to bond if metal). If the underground water pipe to the building is metal it's considered an electrode and you're supposed to use it.