Triplex Sub panel

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Castrovinci

Castrovinci

Member
Location
NJ
All,
I am running an outdoor 100A 120v Three phase sub panel for some truck heaters. I need to do an overhead run of about 200'. I am going back and forth on cost and options of stepping it up to 480 and step back down or just upsizing the wire for voltage drop.

Here is my issue....

Can i run triplex for the subpanel and just run two ground rods outside or do I have to run a quadplex so I also have a ground and neutral? If I can run the triplex I saw somewhere in the forum someones state would not allow the grounded and grounding conductor to be one even though it appeared NEC allows it for a seperate building. I am thinking this can be treated as a seperate building even thought the panel is going to mount on a telephone pole outside in the yard and its not in a building?

If I use a step up and then step back down I can get away with the triplex since my high voltage side does not require a neutral? Downside is a lot more money and labor involved. I am hoping the first option is possible.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
250.32, the applicable section, applies to buildings OR STRUCTURES.
The NEC Definition of a structure is "That which is built or constructed".
Most NEC folks would look at your pole/panel/etc as a structure and enforce 250.32 requiring a separate EGC.
 
jxofaltrds

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
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ESI, PI, RBO
Castrovinci

Castrovinci

Member
Location
NJ
Thank you

Thank you

augie47 said:
250.32, the applicable section, applies to buildings OR STRUCTURES.
The NEC Definition of a structure is "That which is built or constructed".
Most NEC folks would look at your pole/panel/etc as a structure and enforce 250.32 requiring a separate EGC.
Click to expand...


(1) Equipment Grounding Conductor. An equipment grounding conductor as described in 250.118 shall be run with the supply conductors and connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).


That about sums it up! Thanks.
 
S

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
Castrovinci said:
All,
I am running an outdoor 100A 120v Three phase sub panel for some truck heaters.
Click to expand...

I think you need more than triplex... If this is 3 phase and you need 120V and all three phases, you need 4 insulated wires plus a grounding conductor. Does anyone make pentaplex?

Not sure that all the work in transforming the voltage will save you enough in the end, but maybe. If you can make everything 208V and not require a neutral, perhaps the amp loading will be less?
 
Castrovinci

Castrovinci

Member
Location
NJ
suemarkp said:
I think you need more than triplex... If this is 3 phase and you need 120V and all three phases, you need 4 insulated wires plus a grounding conductor. Does anyone make pentaplex?

Not sure that all the work in transforming the voltage will save you enough in the end, but maybe. If you can make everything 208V and not require a neutral, perhaps the amp loading will be less?
Click to expand...

Yes, my original post should of said quadplex:slaphead: and not triplex sorry about that. They don't make anything higher than the quad so no (Pentaplex or a sexaplex:lol:) (according to the supply house) that is why I was trying to just do the three conductors and a neutral and see if there was an exception to ground at the panel and not need an additional wire, but there is not. My only option is if I am going to use two transformers I can then use the quadplex. Trenching is not an option unless the facility wants to front the 30K cost to dig and repair.:jawdrop:
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
I doubt anyone is still that far behind, but note that (i think) 2005 and prior you could "rebond" the neutral at a remote structure. Assuming you are on a cycle later than that, note that triplex and quadplex is not the only option for overhead. The code does permit most wiring methods to be run as messenger supported wiring. This means you could take 4 plus ground SER or MC and fasten it to your own messenger. Seems a little mongrel I know but it is permitted.
 
ActionDave

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
electrofelon said:
I doubt anyone is still that far behind, but note that (i think) 2005 and prior you could "rebond" the neutral at a remote structure.
Click to expand...
Yes, you could as long as there were no metallic connections between the structures.
Assuming you are on a cycle later than that, note that triplex and quadplex is not the only option for overhead. The code does permit most wiring methods to be run as messenger supported wiring. This means you could take 4 plus ground SER or MC and fasten it to your own messenger. Seems a little mongrel I know but it is permitted.
Click to expand...
Done that using TC but it was only to three way some lights.
 
Little Bill

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Castrovinci said:
All,
I am running an outdoor 100A 120v Three phase sub panel for some truck heaters. I need to do an overhead run of about 200'. I am going back and forth on cost and options of stepping it up to 480 and step back down or just upsizing the wire for voltage drop.

Here is my issue....

Can i run triplex for the subpanel and just run two ground rods outside or do I have to run a quadplex so I also have a ground and neutral? If I can run the triplex I saw somewhere in the forum someones state would not allow the grounded and grounding conductor to be one even though it appeared NEC allows it for a seperate building. I am thinking this can be treated as a seperate building even thought the panel is going to mount on a telephone pole outside in the yard and its not in a building?

If I use a step up and then step back down I can get away with the triplex since my high voltage side does not require a neutral? Downside is a lot more money and labor involved. I am hoping the first option is possible.
Click to expand...

Castrovinci said:
Yes, my original post should of said quadplex:slaphead: and not triplex sorry about that. They don't make anything higher than the quad so no (Pentaplex or a sexaplex:lol:) (according to the supply house) that is why I was trying to just do the three conductors and a neutral and see if there was an exception to ground at the panel and not need an additional wire, but there is not. My only option is if I am going to use two transformers I can then use the quadplex. Trenching is not an option unless the facility wants to front the 30K cost to dig and repair.:jawdrop:
Click to expand...

Looks like you said what you meant in the OP.:p
 
kwired

kwired

Electron manager
Location
NE Nebraska
augie47 said:
250.32, the applicable section, applies to buildings OR STRUCTURES.
The NEC Definition of a structure is "That which is built or constructed".
Most NEC folks would look at your pole/panel/etc as a structure and enforce 250.32 requiring a separate EGC.
Click to expand...
It needs separate grounded and grounding conductors whether it is a separate structure or not if the applicable code is 2005 or later.


Castrovinci said:
Yes, my original post should of said quadplex:slaphead: and not triplex sorry about that. They don't make anything higher than the quad so no (Pentaplex or a sexaplex:lol:) (according to the supply house) that is why I was trying to just do the three conductors and a neutral and see if there was an exception to ground at the panel and not need an additional wire, but there is not. My only option is if I am going to use two transformers I can then use the quadplex. Trenching is not an option unless the facility wants to front the 30K cost to dig and repair.:jawdrop:
Click to expand...

You could consider not stepping voltage up and save the cost of one transformer, and just install a 1:1 ratio transformer at the load end with a neutral on the derived conductors.

I have to do a little thinking on this, but it may also be possible to derive a neutral using autotransformers, and they wouldn't need to be as large as a separately derived unit would be. Keeping load balanced would be the biggest trick to keeping them smaller though.
 
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