Grounded Conductor/Neutral

[ccbuilding]

Probably a very simplistic question, but I’m still trying to learn the basics for electrical.

A homeowner ran a circuit from house panel to sub-panel in garage. She ran 2-#2’s and 1-#6. There is a UFER ground in place.

I wasn’t sure if this was a correct configuration, and told her she needed a neutral to complete the circuit properly. She wanted to know if she could use the #6 as her neutral, and use the UFER at the garage as her ground.

Would this work? Can a neutral be smaller in size than the current carrying conductors? Or does she need to run another #2 to be correct?

Thank you.

 

[raider1]

Re: Grounded Conductor/Neutral

First off what is the calculated load for the garage?

The neutral conductor of a feeder can be sized smaller than the ungrounded "hot" conductors provided that it is sized to carry the maximum unbalanced load at the garage and not smaller than what is required by 250.122. (See 215.2(A)(1))

If you are using the 2008 NEC you must run an equipment grounding conductor to the garage, you are no longer permitted to use the grounded conductor for bonding at the separate structure. (See 250.32)

If you are using an older version of the NEC you can use the grounded (neutral) conductor for bonding at the separate structure provided that there are no continuous metallic paths bonded to the grounding system in each building or structure involved.

Chris

 

[ccbuilding]

Re: Grounded Conductor/Neutral

Thank you - should have said we're still using 2005 NEC.

Garage will have a 50 Amp Circuit breaker. - Just providing lighting and a couple of general recepticles.

 

[raider1]

Re: Grounded Conductor/Neutral

Thank you - should have said we're still using 2005 NEC.Garage will have a 50 Amp Circuit breaker. - Just providing lighting and a couple of general recepticles.

A #6 copper conductor has an ampacity of 55 amps at 60 degrees and 65 amps at 75 degrees, so the ampacity of the #6 is plenty to carry the maximum imbalanced load from a 50 amp feeder.

If this is an aluminum #6 then at 60 degrees C you would have an ampacity of 40 amps and at 75 degrees C you would have an ampacity of 50 amps.

Assuming that there are no bonded metallic paths you can use the grounded conductor for gounding and bonding at the separate garage. Make sure that the UFER ground is connected to the grounded conductor at the disconnecting means at the garage and that there is a bonding jumper connecting the grounded neutral conductor at the garage disconnecting means to the equipment enclosure and EGCs.

Also make sure that there is a disconnecting means at the garage in accordance with Part II of Article 225.

Chris

 

[ccbuilding]

Re: Grounded Conductor/Neutral

Thanks Chris

I appreciate the prompt responses.

It is copper, no bonding path, and there is a disconnect at garage, and UFER is connected correctly.

Homeowner just didn't want to have to pull new wires, so you made them very happy.

Thank you again.

 

[raider1]

Re: Grounded Conductor/Neutral

Your very welcome.

Chris

 

[Span]

Re: Grounded Conductor/Neutral

If its a detached garage install a grounding rod is required. Even it has a grounding wire connect at

main panel. The owner need to add a neutral wire, and I'll not mention anything about calculate

unbalance load. I'll just tell them add another #2 for neutral. At sub-panel neutral & grounding need

to seperate, and not allow to bond together.

 

[raider1]

Re: Grounded Conductor/Neutral

If its a detached garage install a grounding rod is required. Even it has a grounding wire connect atmain panel. The owner need to add a neutral wire, and I'll not mention anything about calculate

unbalance load. I'll just tell them add another #2 for neutral. At sub-panel neutral & grounding need

to seperate, and not allow to bond together.

And what are you basing all this on?

250.32 of the 2005 NEC permits a detached garage to be supplied with a feeder that does not contain an EGC and allows the grounded neutral conductor to be used for bonding at the garage. If you do this then the EGC and the grounded conductor will be connected together at the disconnecting means at the detached garage.

As far as requiring the neutral to be a #2 what code section would you cite to require this for this situation?

Chris

 

[Span]

Re: Grounded Conductor/Neutral

As I state it, just forget the neutral max unbalance load calculation, Simply use same size feeder for

neutral and no one will questioning it.

05NEC 250.32 For remote building, If just single branch circuit. Grounding rod not require.

If you have a sup-panel at remote building, grounding will be required, If you have hand book is

locate at P.203 & 204.

Grounding & neutral they are bonding together at main panel is standard. Sub-panel they need

seperated. Why? If you bond them together at sub-panel grounding wire will also carrying return

current too.

Neutral: Alway carry return current.

Grounding: Normaly, no current, unless fault current.

Span

 

[raider1]

Re: Grounded Conductor/Neutral

As I state it, just forget the neutral max unbalance load calculation, Simply use same size feeder forneutral and no one will questioning it.

Why, the NEC permits the neutral to be sized based on the maximum unbalanced load provided that the neutral is sized at a minimum in accordance with 250.122.

05NEC 250.32 For remote building, If just single branch circuit. Grounding rod not require.If you have a sup-panel at remote building, grounding will be required, If you have hand book is

locate at P.203 & 204.

The original poster already stated that there was a concrete encased electrode present. Nothing was ever mentioned about not having a grounding electrode.

Grounding & neutral they are bonding together at main panel is standard. Sub-panel they needseperated. Why? If you bond them together at sub-panel grounding wire will also carrying return

current too.

Neutral: Alway carry return current.

Grounding: Normaly, no current, unless fault current.

Span

The original question was in regards to NOT having an equipment grounding conductor run with the feeder conductors to the garage.

250.32(B) in the 2005 NEC permits a feeder without an equipment grounding conductor to supply a detached garage. If this is done then you MUST connect the equipment grounding conductors together with the grounded conductor at the detached garage or else there is no fault current path back to the main building.

I agree for a "sub panel" supplied by a feeder with an equipment grounding conductor then the EGCs and the neutrals must be kept separate.

Again this changed in the 2008 NEC to no longer permit a detached building to be supplied be a feeder without an equipment grounding conductor.

Chris

 

[Span]

Re: Grounded Conductor/Neutral

Ok, 250.32 (B).2 allow you to connect grounding wire to Structure and electrode. But, if this is new

installation, why not ask them to add a grouding wire.

I didn't said NEC not allowing you to calculate maximum unbalance load. I am saying ,just use same

size as feeder will be easier.

I'm still in 05NEC.

span

 

[raider1]

Re: Grounded Conductor/Neutral

Ok, 250.32 (B).2 allow you to connect grounding wire to Structure and electrode. But, if this is newinstallation, why not ask them to add a grouding wire.

Why ask them to add the extra expense of pulling an EGC when it meets the code as installed?

I didn't said NEC not allowing you to calculate maximum unbalance load. I am saying ,just use samesize as feeder will be easier.

I'm still in 05NEC.

span

Easier for who?

The feeder was already installed with 2 #2 conductors and 1 #6 conductor, are you saying that it is easier to repull the #6 with a #2 then to run a quick calculation and see if the existing #6 is adaquate to carry the maximum unbalanced load?

The original poster said that this feeder had a 50 amp 2 pole breaker so the maximum unbalanced load if everything was 120 volts would be 50 amps and a #6 copper conductor has an ampacity of 55 amps at 60 degrees C and an ampacity of 65 amps at 75 degrees C. Therefore the #6 works just fine for a grounded conductor (Neutral), making the owner replace it with a #2 is a waste of time and money.

Chris