ground rod for each tap fed panel on seperate structures

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dburney

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Brooklet ga usa
I have 6 structures that have a mini power panel/transformer combo that has 3 phase 480v feeding in an underground PVC conduit that come into each mini power panel and then the electrician has used Polaris lugs and tapped off with 2 legs to feed panel transformer primary. They loop in and out of each panel at each structure this way with 3 hots and 1 grounding conductor and feed all 6 mini power panels with 2 of the hots. Please help

I have 2 questions.

1. Is this legal to tap in a panel this way with Polaris lugs and loop from panel to panel?

2. Is it required to install a ground rod at each mini power panel? They do have the mini power panel bolted to the structured steel that is attached to a ground rod. However I don't think this is an approved method.
 
I think that if the six structures are physically separated and the source is anything but POCO service, under current code you would have to run an EGC (either wire or raceway) along with the rest of the supply feeder wires. Then supply a local ground via CEE, building steel, water pipe, rod(s) or whatever else is a code acceptable GES at each structure. The GES will be connected to the EGC but there will be no bond between neutral and ground.
 
dburney said:
.......I have 2 questions.

1. Is this legal to tap in a panel this way with Polaris lugs and loop from panel to panel?
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That's fine.

2. Is it required to install a ground rod at each mini power panel? They do have the mini power panel bolted to the structured steel that is attached to a ground rod. However I don't think this is an approved method.
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If the structure meets the requirements of 250.52 that's fine too.
 
The transformer primary is being protected by the equipment grounding conductor which is tied to the case of the mini power zone. The power zone is bolted to the structural steal by 4 e/8 bolts that are not threaded into the beam just through it and nuts on back side.
 
let me rephrase my question.. how is he providing the overcurrent protection required by Art 450 for his transformer ?
 
Ok sorry about that the power zone is being feed from a 3 pole 40 amp breaker at the mdp then their is a main disconnect breaker at each power zone rated at 15 amps before it goes to the transformer
 
augie47 said:
let me rephrase my question.. how is he providing the overcurrent protection required by Art 450 for his transformer ?
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He sort of described it, and if it is what I think it is it has a primary breaker, the transformer and then a secondary breaker and secondary side panelboard all in one assembly. They usually are even rated for use as service equipment.

What he described sounds fine to me if load calculations are under the feeder capacity, and if the feeder has proper overcurrent protection. Each tap could be 15 amp conductors, as well as the final run to the last unit as outdoor feeders can be unlimited length.

One GEC to each unit at each building should take care of primary and secondary GEC requirements as they are already bonded together within the power zone unit.

Should not need a fifth conductor with the feeder - unless there is 277 volt loads somewhere then you would need a neutral and a equipment grounding conductor in the feeder, but as described so far I don't believe we have any 277 volt loads.
 
Their are no 277 load on the power zone and you are correct on the set up my concern now with it is that it is bolted to the beam with no threaded hole just drilled through with a nut on the back side no paint from the panel has been removed that I can see. Is this an acceptable form of bonding to the steel since the gec I connected to the steel only?
 
dburney said:
Their are no 277 load on the power zone and you are correct on the set up my concern now with it is that it is bolted to the beam with no threaded hole just drilled through with a nut on the back side no paint from the panel has been removed that I can see. Is this an acceptable form of bonding to the steel since the gec I connected to the steel only?
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Though it may be pretty effective to just bolt the equipment to the building steel, I would say most inspectors would still require a wire type GEC to bond to that steel. For one thing I don't think you will find anything in 250 part III that lets you use raceways and metal cabinets or boxes as part of the GEC path, unlike how part VI does include them in being a part of an EGC path.
 
kwired said:
Though it may be pretty effective to just bolt the equipment to the building steel, I would say most inspectors would still require a wire type GEC to bond to that steel. For one thing I don't think you will find anything in 250 part III that lets you use raceways and metal cabinets or boxes as part of the GEC path, unlike how part VI does include them in being a part of an EGC path.
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But with it just being bolted to the steel would it violate 250.8 section A1-8
 
dburney said:
Do you know which part of section 3 days you can not use the case
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The case/enclosure is not listed as a point of termination for a GEC.

250.24(A)(1) General. The grounding electrode conductor connection
shall be made at any accessible point from the load end
of the overhead service conductors, service drop, underground
service conductors, or service lateral to, including
the terminal or bus to which the grounded service conductor
is connected at the service disconnecting means.
 
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