Old farm, center pole

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packerbacker

Member
Location
WI
I am working on a old farm which has a standard center pole, trans at top. At the bottom is a small 200 amp panel feeding 3 sets of overhead tri plex (house, shed, garage). We were asked to change out panel in house. Question being the 3 wire tri plex, with no equipment ground coming from first point of disconnect, do I bond my grounds and neutrals at the panel in the house as well as at pole? I understand this is not code but if i dont bond them in the house, my equipment ground (from rods at house) would not be connected to my grounded conductor at any point other than through earth back to pole. Unfortunantly owner doesnt want to spend money on 4 wire overhead upgrade.
 

kwired

Electron manager
Location
NE Nebraska
Since the overhead conductor is only three conductors you don't have much choice but to bond neutral and ground at load end. AHJ may have something to say about whether or not you can leave the 3 conductor overhead.

I think I would at least run separate equipment ground from your new disconnecting means at the house to the point of attachment to overhead conductors and connect them together at the transition point, that way if the overhead conductors are ever replaced it can be done correctly without having to go inside and possibly change anything. Leave the bonding screw out of the panel also, otherwise all you did was parallel the neutral.
 

kwired

Electron manager
Location
NE Nebraska
Typical install for rural areas although there usually is not a panel at the center pole. A convenience disconnect is what we call them.

sometimes they have overcurrent protection, sometimes they do not. AFAIK State Electrical Division wants to treat these as if there was no overcurrent protection, because POCO usually installs and maintains this switch and can replace with or without overcurrent protection.

At least that is the way they treated them years back even before the changes requiring EGC with all outdoor feeders. Had run into that problem back then because they wanted to ensure that service disconnecting means not necessarily under owners control did not get removed or even replaced with higher capacity overcurrent protection sometime down the road. Instead the general rule was to treat everything leaving that disconnect as though it were service conductors no matter what.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I think you are going to end up with an AHJ call, but I also think what you will find is the Exception to 250.32(B) will apply and you will bond the grounded conductor.
You might want to refer to Art 547.9 where this type installation is discussed. You might note in some cases it's required.
 

kwired

Electron manager
Location
NE Nebraska
Not the kind we wire.....

They're more like an industrial plant than a farm in that aspect.

Those are around here also. But POCO puts a "convenience disconnect" on just about every rural service of 400 amps or less single phase, and three phase 250 volts max is usually that way also. 480 volts they usually provide the disconnect up to 200 amps. Three phase over 250 volts or anything over 400 amps is almost always case by case.
 
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