3 wire garage feed

[Dennis Alwon]

Here is an article by Stallcup that I scanned from a magazine that pertains to the OP's question.

 

[ptonsparky]

We solved a similar problem with a small two car unattached garage by removing the panel in the garage, replacing it with an A/C disconnect that includes a gfci receptacle. We now have a single 20 amp branch circuit feeding a garage. Neutrals & EGs are isolated. All items are gfci protected. No GES required. Plus wehave the disconnecting means. Works if customer does not need or require more than one BC.

 

[Dennis Alwon]

We solved a similar problem with a small two car unattached garage by removing the panel in the garage, replacing it with an A/C disconnect that includes a gfci receptacle. We now have a single 20 amp branch circuit feeding a garage. Neutrals & EGs are isolated. All items are gfci protected. No GES required. Plus wehave the disconnecting means. Works if customer does not need or require more than one BC.

I probably would have made it a 120V panel before doing that.

Interesting point-- my bet is that the way the NEC is written your install is non compliant. I wrote a proposal to change this. The NEC allows a sp switch but the disconnect would have to be service rated. Most a/c discos are not service rated. 225.36

BTW, I have never seen anyone get turned down for it.

 

[ptonsparky]

I probably would have made it a 120V panel before doing that.

Interesting point-- my bet is that the way the NEC is written your install is non compliant. I wrote a proposal to change this. The NEC allows a sp switch but the disconnect would have to be service rated. Most a/c discos are not service rated. 225.36

BTW, I have never seen anyone get turned down for it.

Mozt likely guilty. I believe they have words similar to "Suitable for use as servi e disconnect" on the label inside but will admit to stretching that definition a bit. Sure has worked well for all sorts of small buildings with only one BC to it. Da.g going to jail for sure.

 

[kwired]

I probably would have made it a 120V panel before doing that.

Interesting point-- my bet is that the way the NEC is written your install is non compliant. I wrote a proposal to change this. The NEC allows a sp switch but the disconnect would have to be service rated. Most a/c discos are not service rated. 225.36

BTW, I have never seen anyone get turned down for it.

The NEC also allows a set of 3 way switches to be the disconnect. A non service rated switch of either single throw or pull out style is usually at least indicating of whether it is on or off. Could this exception use better wording --yes.

If you have an inspector that doesn't allow the AC disconnect --- you have an inspector that thinks he is a god and what he thinks is the way it is. (I toned it down quite a bit from what my first thoughts were)

 

[Dennis Alwon]

The NEC also allows a set of 3 way switches to be the disconnect. A non service rated switch of either single throw or pull out style is usually at least indicating of whether it is on or off. Could this exception use better wording --yes.

If you have an inspector that doesn't allow the AC disconnect --- you have an inspector that thinks he is a god and what he thinks is the way it is. (I toned it down quite a bit from what my first thoughts were)

I agree and this exception is only for residential. So if that is the case then it seems as if a mwbc cannot be used for a non residence unless there are non fused disconnects that are service rated. I believe that Chris (Raider) made a proposal to get that changed.

 

[kwired]

I agree and this exception is only for residential. So if that is the case then it seems as if a mwbc cannot be used for a non residence unless there are non fused disconnects that are service rated. I believe that Chris (Raider) made a proposal to get that changed.

The exception:

For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means

What is wrong with a 2 pole snap switch?

In the rare occasion where a residence may have 120/208 three phase one should even be able to run a MWBC with all three phases and a 3 pole snap switch - it is still one branch circuit.

Again just my opinion but I trust an AC disconnect to be off if I am working on something in that garage, the allowed 3 way switch ... not a chance of trusting that someone will not turn on the other switch that may not even be within the building, now whatever it is that I am working on may be energized.

 

[Dennis Alwon]

I am not following. I was saying that snap switches or a/c discos cannot be used for non residential separate structure disconnects unless the a/c disco is service rated. IMO, this would make using a MWBC or single branch circuits non compliant in non residential settings.

 

[kwired]

I am not following. I was saying that snap switches or a/c discos cannot be used for non residential separate structure disconnects unless the a/c disco is service rated. IMO, this would make using a MWBC or single branch circuits non compliant in non residential settings.

That is correct. Thread topic is a garage at a dwelling.

 

[ritelec]

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.

Interesting.........would that be just a the "building" electrical service, or even a separate structure as in a detached garage? Wouldn't a panel with more than 6 throws of the hand at the detached garage be just a feeder sub panel?

(although I realize a rod, disconnect means have changed in the last few code changes).

But still, would not it be a feeder, and not a service?

 

[ritelec]

"Suitable for use as service disconnect"

Again.........is the detached garage power considered a "service"?

 

[iwire]

Again.........is the detached garage power considered a "service"?

No, not if it is supplied from another buildings service.

But it does not matter because in most cases 225.36 requires a service rated disconnecting means for the feeder to a detached building.

ARTICLE 225
Outside Branch Circuits and Feeders

II. Buildings or Other Structures Supplied by a
Feeder(s) or Branch Circuit(s)

225.36 Suitable for Service Equipment. The disconnecting
means specified in 225.31 shall be suitable for use as
service equipment.

Exception: For garages and outbuildings on residential
property, a snap switch or a set of 3-way or 4-way snap
switches shall be permitted as the disconnecting means.

 

[ramsy]

Article 100, definition of "Feeder"

Read the definitions of feeder and branch circuit.

Thank you. I see having identical amperage breakers at service & disconnect, using identical wire doesn't matter if all conductors from power source to "final branch-circuit overcurrent device" are feeders.

If you have breakers in the garage, you have a feeder, not a branch circuit.

Yes, if inspectors see a breaker as outbuilding-branch disconnect they can enforce the feeder definition, and force Grounding-Electrode Systems (GES). Snap-switch disconnects at residential outbuildings clarify a branch circuit for the inspector, and keep out the GES.

 

[Little Bill]

No, not if it is supplied from another buildings service.

But it does not matter because in most cases 225.36 requires a service rated disconnecting means for the feeder to a detached building.

Besides a label inside, what makes a disconnect "suitable as service equipment"?
Or what determines the rating as "service rated"?

 

[Dennis Alwon]

Besides a label inside, what makes a disconnect "suitable as service equipment"?
Or what determines the rating as "service rated"?

Not sure exactly however the a/c disconnects usually do not have separate neutral and equipment ground bar. I would generally just splice the neutrals and use the grounding bar for the egc.

Here is a UL bit that doesn't tell us much. I think the question is why the disco needs to be suitable as service equipment since it is not service equipment.

24. A panelboard intended for service equipment use must have the marking “Service Disconnects” near the switch or circuit breaker handles. If this is not done in the factory, pressure sensitive labels must be provided. This marking identifies the service disconnects when branch disconnects are
also present. This is required by Section 230.70(B) of the NEC.