From service pedestal to house...3 or 4 wire?
- Thread starter c_picard
- Start date
- Status
102 Inspector
Senior Member
- Location
- N/E Indiana
- Occupation
- Inspector- All facets
IMO, Yes a 4-wire system is requierd based on 250.32(D) of 2008 edition. The service pedestal qualifies as a structure and any wiring from that point of main disocnnect becomes a feeder.
Ravenvalor
Senior Member
- Location
- Piedmont region of NC
What if you run 2 hots 1 neutral and derive your ground from ground rods at the house?
Hendrix
Senior Member
- Location
- New England
Yes IMO
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
To be real concise, we dont know that the disconnecting means for the house is located remotely - If it were located nearest the point of entry then 250.32(D) wouldnt come into play. I would say that 250.24(A)(5) is generally the rule that says we cant rebond the neutral.
Also would comment that there is no NEC requirement for the disconnect at the meter pedestal so if there was not one, the conductors from the meter to the house could still be three wire. Meters are pretty much invisible to the NEC
without the disconnect at the meter you could do this and bond the ground rods, equipment grounds and neutral together at the house. With the disconnect, be careful here: you will end up without a low impedance path back to the source. your equipment would be connected to dirt as required, but you would not clear faults.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
If the disconnect at the meter has OCPD, then your bond should be there and a 4-wire would need to be run to the house.
A ground is not derived from a ground rod. The ground rod is not for ground, it is for lightning and surges.
In the OPs case, he would still need a ground rod at the house, but not for grounding of the service. It would also not connect to the grounded conductor, only the panel and EGC.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I dont see how it could be code compliant to have a service disconnect without a OCPD in or adjacent to it.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
You can not use the earth as an equipment grounding conductor.
I'll give you an example of why. Lets say you have a ground rod with an overall resistance of 10 ohms (which is pretty low for a ground rod in many places) If we applied 120 volts across this 10 ohms (which is what will happen during a ground fault condition) using Ohm's law we will only have 12 amps of current flow through this path. That will mean everything connected to the equipment grounding conductor will be at same potential as the ungrounded conductor that developed the fault (there will be only a small drop in voltage because of voltage drop on the incoming "hot" conductor, making shock hazards around anything connected to the equipment grounding conductor. Add to that since it is only 12 amps of current even a 15 amp overcurrent device will carry that load indefinitely and by its design will not see a trip condition.
Use a very low resistance "wire conductor" instead of the earth as this fault path and the current will be hundreds or even thousands of amps (depending on the ability of the supply and actual resistance of the conductor). This kind of current level means nearly instantaneous tripping of the overcurrent device and removal of the hazardous voltages/currents that would be present if not for the operation of the device.
mwm1752
Senior Member
- Location
- Aspen, Colo
I am not a big fan of the ECG in a lateral run remotely (further than 50' & not within sight, an observation not code) from the structure. IMHO giving a lighting strike more paths to us in order to get to earth thru equipment is more potential for equipment damage. That being said - overcurrent device as a main disconnect makes the lateral a feeder, enough said -- some meters have a disconnect intergal to them, or if the disconnect is unfused then the lateral is unfused making the service point at the structure IMO. Some say the meter location described is considered a structure & therefore the ECG should be inserted. I have had interpretations from code authors refering the meter location as electrical equipment and not a structure. The NEC 2014 addresses the meter ?METER DISCONNECT NOT SERVICE EQUIPMENT.? Kinda a tangled web.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Who cares whether it is a structure or not? I dont see that that has anything to do with it. service conductors can be run along one structure to feed another. There is no requirement to turn them into a feeder as long as they dont pass thru the first structure.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Once you hit an overcurrent device they are no longer service conductors, they are feeders whether multiple structures comes into play or not.
See definition of service conductors in article 100. It doesn't mention overcurrent devices but does mention service disconnect.
A service disconnect will have an overcurrent device associated with it, 230.91 tells us this.
Last edited:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Or, looking at it another way, if the disconnect is not associated with an overcurrent device, it is just a random POCO disconnect, but not a service disconnect.
- Occupation
- Licensed Electrician
A slight variation of this is the way meter pedestals were treated where I live. All of them have a 200A breaker in them but since the pedestal belonged to the POCO it was not considered the first disconnect.
Then someone got a wild idea that we needed a fourth wire to that pedestal and managed to convince the powers that be to make us pull that fourth wire.:thumbsdown: Sad to see natural resources that could serve future generations wasted.
The only way I would consider the Breaker inside a (Power Company provided) Pedestal Combo Meter Main "Not" the first means of disconnect, would be if the Power Company put their seal on the access cover to the Breaker.
Otherwise I feel a 4 wire feeder is required from that point on.
JAP.
Otherwise I feel a 4 wire feeder is required from that point on.
JAP.
- Occupation
- Licensed Electrician
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I know very well the difference between sec and feeders. I interpreted the preceding post as implying a disconnect is required at a meter pedestal structure.
From the 2008 code (I think thats the cycle it changed) structure or not, you would need a 4 wire feeder after the service disconnect
takelly
Member
- Location
- South dakota
If the meter and disconnect belong to the POCO the NEC would not apply to any of their equipment.
If the wires come from the POCO equipment that is not covered by the code wouldn?t the wires be service conductors.
90.2 Scope.
(B) Not Covered.
(5) Installations under the exclusive control of an electric utility where such installations
c. Are located in legally established easements or rights-of-way
If the wires come from the POCO equipment that is not covered by the code wouldn?t the wires be service conductors.
90.2 Scope.
(B) Not Covered.
(5) Installations under the exclusive control of an electric utility where such installations
c. Are located in legally established easements or rights-of-way
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
As has been mentioned, ownership by POCO or limited accessibility by POCO could make a difference and this may be seen differently by different AHJ's.
If we have a pedestal with a meter and no overcurrent devices, we do not have a service disconnect, we still do have a separate structure but have not created a feeder since there was no service disconnect. Put a service disconnect in there and you have changed anything on the load side of it to a feeder. Prior to 2008 NEC you could still bond the grounded conductor of feeders supplying separate buildings or structures at the load end. Now you can only do this via exceptions that allow you to use an existing feeder that at one time did not require a separate EGC.
Does it use more copper or aluminum, or even require a larger raceway? yes.
Does it decrease voltage to ground at the load end? yes. If the grounded conductor is carrying current there is a voltage drop on that conductor, an equipment grounding conductor (with no additional bonds to the grounded conductor) only carries current during abnormal conditions and would only have a voltage drop on it when it is actually carrying current.
Are there ways around having to follow this rule? yes. Don't put in the service disconnecting means at the metering equipment if at all possible and then you do not create a feeder.
Is the rule perfect for all situations - probably not. One problem with our voltage and distribution systems here in North America and the creation of "stray voltages" is having loads that utilize the grounded conductor, but since we have so much of those kinds of loads we are kind of stuck with finding other ways to minimize the problems created.
mwm1752
Senior Member
- Location
- Aspen, Colo
Seems like there is an agreement on ownership due to the point of service. Legally a fourth wire could be or is not required in identical situations depending upon whether the NEC has jurisdiction over the installation. Shouldn't the reasoning in the install of the EGC be based upon life safety and not politics. Will someone, based upon life lafety, justify the EGC installed in feeder situations of remote service equipment near solidly grounded transformers to a structure with a solid electrode system.
None that I can come up with right off hand, just try to follow the rules, and the rules say the 4th wire must be installed past the first means of disconnect. In my opinion that point is at the breaker in the Meter Pedestal, although it may be somewhere else in your opinion, and thats fine too.
- Status