Switch box wiring to a garage panel

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  #1  
Old 06-30-06, 10:15 AM
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Question Switch box wiring to a garage panel

Ok This is what I have to work with.
I'm hooking up to an existing 60amp switch box that is connected directly to the meter on an electric pole next to the garage. I got some free tryplex #2 Aluminum with ( it is just 3 #2 wires twisted together) I plan on running this in 1 1/4 conduit from the pole to the garage.It's about a 18 foot run.
I plan on feeding this into a 100 amp panel box.
My question is do I need to run a gound wire back to the switch box, or in stall a groud rod for the panel in the garage, or can I just jumper the wire and ground in the garage panel box.
I for got to mention.
The electric pole outside has a ground rod next to it and the main meter and the 60 amp switch box is grounded to it.

Thanks. Jim Deitner
 
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  #2  
Old 06-30-06, 12:12 PM
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You require two ground rods at the disconnect box on the pole. You require two ground rods at the garage. You are not required to run a ground wire between the box and the garage.
 
  #3  
Old 06-30-06, 12:28 PM
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What do you mean I require 2 gound rods at the pole?
and 2 rod rods at the garage?
 
  #4  
Old 06-30-06, 12:30 PM
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A single ground rod is not enough. Two are required.
 
  #5  
Old 06-30-06, 12:45 PM
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I'm thinking if this is his main disconnect immediately after the meter he would be required to run a four wire feeder to the garage, otherwise if only three wires he would have to bond his neutral and ground at both the main disconnect and the garage panel (load side) which isnt allowed. Thinking wrong maybe...?

Edit: If not in rigid metal conduit.

Also I dont think if this is overhead triplex (bare neutral as messenger) that you can put it in conduit, nor can you enter the building with it.
 

Last edited by Roger; 06-30-06 at 12:58 PM.
  #6  
Old 06-30-06, 06:47 PM
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I'm thinking if there are no other metal paths between the box and the garage then no neutral is required.
The wire definitely needs to be thwn to go in underground conduit.
 
  #7  
Old 06-30-06, 08:53 PM
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Joe please bear with me on this. If we were feeding the garage from a main panel via a double pole breaker in the main panel and that main panel contained the main disconnect and that main panel is located in another building remote from the garage.....I would agree you could run a three wire feeder... no metallic paths considered.
If however this 60 amp switch ( I am assuming this is a 60 amp main breaker disconnect) is fed by the meter... it is the main disconnect (service rated) to the garage panel. You would then be required to bond the service neutral to an effective ground fault path at the main disconnect and would therefore need an effective ground fault path to the panel in the garage to allow ocpd on branch circuits in the garage to trip out on fault. You could not use the neutral for the fault path between the 60 amp main disconnect and the garage panel. This is not a common service to a meter on a house then to a house main panel then to a remote garage... this is a service to a garage. I believe it would be treated differently.

Just my 2 cents

Roger
 

Last edited by Roger; 06-30-06 at 09:04 PM.
  #8  
Old 06-30-06, 09:25 PM
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Here is my 2 cents.

The disconnect at the pole is the service. It requires a grounding electrode system at the pole. The garage is a sub of this service

The garage can be fed with 3 wire if there are no other metal paths betwen the two panels and no GFI to the garage.

Joed, you carry the neutral always. It is the ground that would not need to be taken with.

The neut and ground would then be bonded at the garage as well as at the pole sevrvice with GE system at the garage as well.

yes Roger, it is allowed see ref below
--------------------------

alternate method

If you take 4 wire, then the neut and ground are not bonded at the garage but ground rods are still needed at the garage for the EGC and bonded to building steel etc. as typical.

ref: NEC 250.32(B)(1) and 250.32(B)(2)
-------
 

Last edited by nap; 06-30-06 at 09:48 PM.
  #9  
Old 06-30-06, 11:26 PM
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So are we saying that the disconnect on a pole is a seperate building or structure. 250.32 refers to seperate building(s) or structure(s) supplied from a common service. Otherwise no grounding connection can be made to the grounded conductor on the load side of the service disconnecting means 250.24(A)(5).
There are 2 exceptions pointed to in 250.142 that would possibly apply and the grounding connection made to the grounded conductor....

1.) You can make the connection to the load side of the main disconnect to seperately derived systems according to 250.30(A)(1).

2.) Between seperate buildings according to 250.32 (B)(2).

I dont see see either in this case.

So unless that pole mounted disconnect is considered a building or structure. I still respectfully disagree.

Roger
 

Last edited by Roger; 06-30-06 at 11:37 PM.
  #10  
Old 07-01-06, 07:05 AM
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Originally Posted by Roger
So are we saying that the disconnect on a pole is a seperate building or structure. 250.32 refers to seperate building(s) or structure(s) supplied from a common service. Otherwise no grounding connection can be made to the grounded conductor on the load side of the service disconnecting means 250.24(A)(5).
There are 2 exceptions pointed to in 250.142 that would possibly apply and the grounding connection made to the grounded conductor....

1.) You can make the connection to the load side of the main disconnect to seperately derived systems according to 250.30(A)(1).

2.) Between seperate buildings according to 250.32 (B)(2).

I dont see see either in this case.

So unless that pole mounted disconnect is considered a building or structure. I still respectfully disagree.

Roger
I worry less about the terminology of it being a building or structure and more about it either being the "service disconnect" or not. If it is the service equipment (which it is) then I believe tthe 250.32 references apply. The garage most assuredly is a seperate structure supplied from a common service because the service is not contained within or on the garage. I believe that is the key point. Technically, the pole service could be used to serve other buildings as well if desired.
(load rating not in consideration here) This would make it a "common service" to all buildings.

250.24 refers to the service for a particular building and the connections within that building. I believe the exception in that section for 250.32 applies in this situation.

250.142 does the same.

----------

While the non-bonded seems to be more acceptable on those that post here, I believe the 3 wire system to be equally legal as long as the disqualifiers do not apply.

I still cannot find any reference as to the legality of the triplex in conduit though. This itself may make the install design a moot point.

BTW: I appreciate the "respect" part but I've done nothing to earn that yet. I am trying, the same as all others here, to help the poster install a safe and legal electrical system. When I am all knowing, then I can expect respect, until then, I make mistakes and thank those that feel I deserve any respect.
 
  #11  
Old 07-01-06, 03:29 PM
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Hmmmm...well this is my take on 250.32(b). If two or more buildings are supplied by a common service then the three wire is permissable with bonding of the grounding means and grounded conductor at both buildings panels. I only see one building in this case and a pole mounted service disconnect remote from that building. However if the pole mounted disconnect is considered a building or structure (btw it may well be just that) then a 3 wire is permissible. A structiure according to the NEC..."that which is built or constructed". Arguably that could very welll be a meter on a pole and pole mounted main disconnect. I've been told it isnt and told it is by many electricians. I am of the opinion that it is a stretch to call a pole... as we have here.... a structure, but many do in the area I work in. When we do farm poles (you refered to the possibility this service supplying other structures) that feed several buildings we do indeed run three wire feeders unless we are having to deal with equipotential planes for a building housing livestock. Generally when we are feeding only one buildings panel from a remote pole disconnect we run a four wire feeder and bond to the grounded conductor in the main disconnect enclosure only... carrying the equipment ground conductor to the buildings panel.
And it may be required anyway as a heck of alot of inspectors are not keen on 3 wire feeds for situations like we have here. At any rate you may be right I'm just having difficulty with the pole being a structure or building. I agree this is not a point of great worry as far as terminology is concerned but none the less it is ambiguous in itself almost to the point of being an oxymoron statement when we compare 250.24(A)(5) and 250.32(B). The whole idea of course is to prevent objectionable current on the metal bonded parts of the system. In my opinion 250.32(b) is contradictory to preventing objectionable current, though oddly it is acceptable in the case laid out in 250.32(B).
Nice discussion BTW.

I did find this in trying to get to the bottom of this. The last four posts are the ones that apply, the entire discussion lends some clarification to what we are discussing here. It lends support to you and Joeds opinions. So I'm starting to feel like I may have climbed out on a skinny limb.....

http://www.mikeholt.com/code_forum/a...p/t-57878.html

Roger
 
  #12  
Old 07-01-06, 03:53 PM
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Na, it better be a huge limb because there are a lot of electricians out there with you. This is why there is so much trouble filling the bill when it comes to the code and the AHJ gets to make the call.

Now do note; I stated it is permissable (not required). I'm glad you brought up the farm thing. That is the reason why your way may very well be better.

I swear that the code committee sits around just trying to figure out ways to confuse everybody. It happens every time they make a change, which is absolutely every three years.

I think if somebody would poke them all in the eye with a stick every time they write stuff like this, they would start having everything make sense instead of listing 72 exceptions to everything and then adding FPN that are supposed to explain but often end up adding confusion themselves.

Maybe the OP should ask his local inspector because he is the guy that gets to make the final call anyway and he may prefer(require) one method over the other.
 
  #13  
Old 07-01-06, 06:26 PM
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Nap, I totally agree with you, it seems to me that if there needs to be several "exceptions" to the rule then the rule itself needs to be changed.

Here is my take, and while I have had to deal with electrical codes my entire working life I am neither an electrical engineer nor an electrician.

IF this 60 Ampere switch contains overcurrent protection (fuses or a circuit breaker) then this would constitute the SERVICE and any leads/cable leaving would be a FEEDER and as such the four-conductor rule (hot, hot, neutral, ground) would apply. If the 60 ampere switch DOES NOT also have overcurrent protection then the wires leading from it to the first overcurrent protective device (OCPD) would continue to be classified as part of the service and all rules pertaining to services would apply.

Bottom line is that the local code ALWAYS takes precedence and it is in the local code, and its interpretation by the local AHJ, that needs to be followed.
 
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