3 wire garage feed

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arnettda

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I am doing some work after a home was inspected before closing with the new buyer. There is a three wire system to a garage that showed up on the list. There are no ground rods driven at the garage either. Is the only way I can make this legal is two trench new wire to the garage? There is sub panel in garage with 3 breakers being used. Would ground rods always been required at the garage? Can I say it was legal at the time of installation? There is no main disonect at the garage but that was not on the list. If I get it to just two breakers would it then be legal?
Thanks for you help.
 
If there are no other ground paths, it is existing under 2005 or earlier, and you install a GES-ground rods you might skate.

250.32(B)(1) exception

Exception: For installations made in compliance with previous
editions of this Code that permitted such connection,
the grounded conductor run with the supply to the building
or structure shall be permitted to serve as the ground-fault
return path if all of the following requirements continue to
be met:
(1) An equipment grounding conductor is not run with the
supply to the building or structure.
(2) There are no continuous metallic paths bonded to the
grounding system in each building or structure involved.
(3) Ground-fault protection of equipment has not been installed
on the supply side of the feeder(s).
 
The amount of breakers for disconnect of the structure is 6.

225.33 Maximum Number of Disconnects.
(A) General. The disconnecting means for each supply
permitted by 225.30 shall consist of not more than six
switches or six circuit breakers mounted in a single enclosure,
in a group of separate enclosures, or in or on a switchboard.
There shall be no more than six disconnects per
supply grouped in any one location.
 
jumper said:
If there are no other ground paths, it is existing under 2005 or earlier, and you install a GES-ground rods you might skate.

250.32(B)(1) exception

Exception: For installations made in compliance with previous
editions of this Code that permitted such connection,
the grounded conductor run with the supply to the building
or structure shall be permitted to serve as the ground-fault
return path if all of the following requirements continue to
be met:
(1) An equipment grounding conductor is not run with the
supply to the building or structure.
(2) There are no continuous metallic paths bonded to the
grounding system in each building or structure involved.
(3) Ground-fault protection of equipment has not been installed
on the supply side of the feeder(s).
Click to expand...

If I use this exep would I need a ground rod?
 
With more than one circuit in the garage - a given, since you say it's feeding a panel - there's no way to avoid needing a grouning electrode (ground rod) at the garage.

They really should have run a fourth wire, and kept the ground isolated from the neutral. Still, it was quite possible to read the code as allowing the installation you describe, right up to the 2008 edition. 2008 clarified that you cannot treat this garage as a 'separate service.'
 
Might be possible to swith to 120 volt sub-panel and use existing wire if 240 v not needed. This would give you Ungrounded/grounded/ GEC and then install ground rods as others have stated. Make sure over-current device at main panel sized properly for conductors used.
 
i thought that when feeding a detached garage you can use the gec from the panel in the house as means for grounding and that a grounding electrode would not be needed
 
liquidtite said:
so you dont need a grounding electrode as long as you have only only onebc that supplies the structure.
Click to expand...
That is correct...as long as you have a single branch circuit. If you have breakers in the garage, you have a feeder, not a branch circuit.
 
don_resqcapt19 said:
..If you have breakers in the garage, you have a feeder, not a branch circuit.
Click to expand...

225.36 Exception describes a snap switch as fulfilling disconnecting means for Class U garage branch circuits.

That doesn't exclude a 2-pole breaker in/outside of garage, for same MWBC, if enclosure is listed as service equipment and sized exclusively for one 2-pole disconnect.
 
Last edited:
ramsy said:
225.36 Exception describes a snap switch as fulfilling disconnecting means for Class U garage branch circuits.

That doesn't exclude a 2-pole breaker in/outside of garage, for same MWBC, if enclosure is listed as service equipment and sized exclusively for one 2-pole disconnect.
Click to expand...
If that breaker is providing overcurrent protection to the circuits it the garage, the line side of that breaker is a feeder and not a branch circuit. If the garage is served by a feeder, a grounding electrode is required.
 
ramsy said:
Yea, and good luck making sense of it all.
Click to expand...

It makes total sense. The NEC allows us to use either a single 2 wire circuit, a MWBC or a feeder to feed a detached structure. When you use a MWBC or 2 wire circuit in a residential application a single pole snap switch is allowed and no grounding electrode is required. When you install a feeder to that structure then you must install a panel that is suitable as a service disconnect and one must install ground rods and use any other electrodes at the building. The grounding electrode conductor must be isolated from the neutral bar and attached to the grounding bar.

There is an exception before 2008 NEC that allowed a 3 wire feeder to the structure if there were no other metallic pathways such as phone lines, water lines etc. that went to the structure. In that case the neutral and the electrode were bonded to the can.

We are allow the 6 handle maximum disconnect rule to disconnect all circuits in the structure or we can use a main disconnect (my preference).

MWBC- no electrode but main disconnect is required- could be a SP switch

Feeder New- separate grounding and grounded conductors that are isolated at panel- electrode also required- disconnect needed or 6 handle rule

Feeder Existing - grounded conductor only- no metal pathways- electrode and grounded conductors are connected to the enclosure- disconnect needed or 6 handle rule
 
jumper said:
The amount of breakers for disconnect of the structure is 6.

225.33 Maximum Number of Disconnects.
(A) General. The disconnecting means for each supply
permitted by 225.30 shall consist of not more than six
switches or six circuit breakers mounted in a single enclosure,
in a group of separate enclosures, or in or on a switchboard.
There shall be no more than six disconnects per
supply grouped in any one location.
Click to expand...

Also before the 2008 NEC was the "lighting and appliance" panelboard. If 10 percent or more of the breakers were line to neutral loads the panel needed a main overcurrent device (either in or ahead of the panel)

One breaker out of six is more than 10 percent - so all these small panels in places like that needed a main. I suppose if the building was supplied by a feeder you were covered as long as the feeder overcurrent did not exceed the amp rating of the panel.
 
don_resqcapt19 said:
If that breaker [used for garage disconnect] is providing overcurrent protection to the circuits it the garage, the line side of that breaker is a feeder and not a branch circuit.
Click to expand...

How does a branch circuit fed from one breaker become a feeder after adding another breaker as the required disconnect. Code reference please.

Like Biblical theology, the NEC seems subject to interpretation, but it's not clear who's point of view is twisted.
 
ramsy said:
How does a branch circuit fed from one breaker become a feeder after adding another breaker as the required disconnect. Code reference please.
Click to expand...
Article 100, definition of "Feeder"

Roger
 
ramsy said:
How does a branch circuit fed from one breaker become a feeder after adding another breaker as the required disconnect. Code reference please.

Like Biblical theology, the NEC seems subject to interpretation, but it's not clear who's point of view is twisted.
Click to expand...

Read the definitions of feeder and branch circuit.
 
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