Four wire feed from pole service to house

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nickmcburney

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250.4A5 states that a ground rod cannot be considered a effective path to ground. If I have a 200 amp pole service 300' from a house should I run a four wire feed #6 EGC and sized wires or just run a 3 wire feed. Is the pole considered a structure and must therefore abide by the rules for 4 wire feeds between buildings. It seems to me that by running a four wire feed you are increasing the resistance along the low impedence path back to PG&E. (A #6 vs say 150kcmil, the sized neutral.)
 
nickmcburney said:
250.4A5 states that a ground rod cannot be considered a effective path to ground. If I have a 200 amp pole service 300' from a house should I run a four wire feed #6 EGC and sized wires or just run a 3 wire feed. Is the pole considered a structure and must therefore abide by the rules for 4 wire feeds between buildings. It seems to me that by running a four wire feed you are increasing the resistance along the low impedence path back to PG&E. (A #6 vs say 150kcmil, the sized neutral.)
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Where is the Service Equipment located? On the pole 300' from the house or On the House? Not the POCO meter, but the Service Disconnect? Our inspectors do not normally consider a POCO disconnect as SE. Yours may.

Poles with no utilization equipment mounted on them would not require a separate EGC.

250.4 (3) & (4) require "...in a manner that establishes an effective ground-fault current path." IMO if the #6 EGC is insufficient, than you need to increase the size until it is.
 
nickmcburney said:
250.4A5 states that a ground rod cannot be considered a effective path to ground. If I have a 200 amp pole service 300' from a house should I run a four wire feed #6 EGC and sized wires or just run a 3 wire feed. Is the pole considered a structure and must therefore abide by the rules for 4 wire feeds between buildings. It seems to me that by running a four wire feed you are increasing the resistance along the low impedence path back to PG&E. (A #6 vs say 150kcmil, the sized neutral.)
Click to expand...
You are misreading what the article actually says. And the reason has been the topic of hundreds of posts and numerous suggestions for major terminology changes.

A ground fault current path is NOT a path to ground!
It is a path back to the (grounded) supply neutral for fault clearing.
The article recognizes that no earth ground (whether rod, ring, CEE, etc.) shall be considered as a fault clearing path. That means that it cannot be relied upon to conduct enough current to open an OCPD (at least not at building wiring voltages.)

The fault current path for a ground fault (slightly misleading term) usually consists of the EGC back to the service disconnect at which point it goes in series through the POCO grounded neutral back to the transformer neutral.

I do not see how you get the idea that running a four wire feeder puts more resistance into the ground fault path than a three wire feeder.
 
You certainly picked one of mt pet peeves -- Correct answer, any circuit protected by a fuse, breaker is now a feeder -- ECG is installed -- I and few out there disagree weather the electrical equipment mounted on a power pole is a structure. You may run a service lateral from transformer to a building withou an EGC though the grounded conductor will be bonded to some type of electrode system at each end of the circuit. But now you insert a disconnect at that same transformer 300' or so away you shall insert an EGC in your circuit wiring not to be bonded to the grounded conductor at the load end. My understanding of the EGC has to do with other conductive installations such as water pipe that can have a continuity with other structures in the same vicinity. Current takes all paths and a grounded conductor inbalance has current. Trouble is you can have a building that recieve service from the same water piping system having one service with the grounded conductor bonded at the disconnect by the transformer and the other bonded at the building served which would in essence create the issue that the code is trying to avoid. Adding the EGC IMO only gives a better chance of paralell path just by being installed - without it there is noway a mistaken connection would cause the path. Granted we are talking about a remot type first disconnect. Every circumstance has special needs.
 
There is nothing wrong or prohibited with having parallel paths in the EGC network or anywhere in the GES.
Just don't let them parallel the grounded conductor (usually the neutral.)
 
GoldDigger said:
There is nothing wrong or prohibited with having parallel paths in the EGC network or anywhere in the GES.
Just don't let them parallel the grounded conductor (usually the neutral.)
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The parallel I'm referring to is the grounded conductor being parallel to the GEC.
 
Thanks you for feedback.

Thanks you for feedback.

I understand that ground rods are not to be used for anything other then lighting protection though they may provide an effective path to ground ie high ground water. the code does not seem to say clearly whether a pole is considered a structure and therefore MUST include a 4 wire feed. If it is not considered a structure then a 4 wire feed is not required. Is that true?

In this situation the main service disconnect is on the pole mounted service which is 300' away.

The panel also has 24 breaker slots. There is one GFI plug on the main service disconnect. Does the presence of any breaker or the potential for a breaker other then the main disconnect at the pole make the conductors from the pole a feeder vs not?

I was assuming that #6 in conduit going 300' would introduce more resistance then say a sized neutral for a 200 amp feeder. smaller wire=more resistance. A #6 is all that is required for a EGC for 200 amps. Say my 50 amp welder shorts out and I am a 4 wire system all the way from the pole 300' away. Can the #6 EGC just melt? Its just seems more dangerous to use a smaller wire over that distance. The intent of the fourth wire was to guard against current following a parrall path between buildings. Where is the potential parrallel path between this pole and the house? There isn't one. I don't think the intent of the code for 4 wire feeds makes sense here and provides less of a path back to PG&E then using the neutral wire.

Your thoughts are greatly appreciated.
 
POCO opinion again...we supply power as single phase, three wire for residences. That does not include a ground. Any grounding takes place at the service disconnect. Call it a structure if you want. Since a fault current ultimately returns to the transformer neutral, any fault clearing will require a low impedance path back to that neutral. A long secondary from the transformer to the Service Disconnect bonding would seem to add fault return impedance, but the utility does not allow parallel ground fault return paths back to the system neutral. All fault return current is on the neutral (grounded) conductor. Lots of reasons, such as remote grounds, etc, but that's that way we do it. The Service is considered any conductors up to the Service Disconnect, regardless of where it is located. Our jurisdiction stops there. That may be off the OP subject, but just thought I'd throw it in.
 
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