Detached Garage

[george t. everett]

I have to supply power to a one car detached garage. There will be 2 outlets, two lights & a garage door opener. I would like to feed it with a 3 wire #12 wthe ground. Can I use a double pole 20 amp switch as the disconnect in the garage?

 

[hurk27]

Re: Detached Garage

Yes you can the nec even allows you to use single-pole switch's as long as you have handle ties but there maybe no more than six ties as this would violate the six movement of the hand rule.

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.


225.33 Maximum Number of Disconnects.
(B) Single-Pole Units. Two or three single-pole switches or breakers capable of individual operation shall be permitted on multiwire circuits, one pole for each ungrounded conductor, as one multipole disconnect, provided they are equipped with handle ties or a master handle to disconnect all ungrounded conductors with no more than six operations of the hand.

 

[frank]

Re: Detached Garage

if you have more than one circuit to a detached garage you must have a ground rod and a disconnect.

 

[don_resqcapt19]

Re: Detached Garage

Frank,
A multiwire branch circuit is a single circuit.
Don

 

[curt swartz]

Re: Detached Garage

Don,

I'm not sure I agree with you on that.

210.4(A) A multiwire branch circuit shall be permitted to be considered as multiple circuits.

While this does not require it to be considered as multiple circuits I would guess that in the case of a separate building most inspectors would consider it multiple circuits.

 

[tom baker]

Re: Detached Garage

For this purpose, the multiwire branch circuit is considered a single branch circuit, see 210.4 (A). The disconnect can be a snap switch see 225.26 exception and Fig 225-16 in mike holts understanding the NEC. Ground rods are not required at separate building or structure that has only one branch circuit 250.32 (A) exception, see fig 250-86 in mike holts understanding the NEC.

 

[curt swartz]

Re: Detached Garage

Tom,

Your 210.4(A) must read different than what's in my book since I don't see anywhere that it says that a multiwire circuit is always single circuit.

210.4(A) Branch circuits recognized by this article shall be permitted a multiwire branch circuits. A multiwire branch circuit shall be permitted to be considered as multiple circuits. All conductors shall originate from the same panelboard.

The second sentence says that they shall be permitted to be considered as multiple circuits and I think many inspectors would do so in the case of a separate structure. I don't think the intent of the coded was to only require a grounding electrode system if you have multiple grounded conductors run to the building. I think the excepting was for structures that have very limited loads and only require a single 15 or 20 amp two wire circuit.

I do agree that a switch is an acceptable means of disconnect.

 

[don_resqcapt19]

Re: Detached Garage

Curt,
The code wording implies that a multiwire circuit is normally considered a single circuit. It says that it is "permitted" not required to be multiple circuits. I don't think that it is within the inspectors authority to require me to consider it as multiple circuits. I believe that is up to the designer/installer.
don

 

[david]

Re: Detached Garage

Not all multi- wire branch circuits are multiple circuits. Most multi wire branch circuits feed ranges and dryers and the like.

The wording in the code has the effect of allowing you as the designer when installing multiple circuits as multi-wire to choice to use single pole breakers for multiple circuits (not all multi-wire circuits) it further stipulates that the multiple circuits must originate from the same panel.

I see nothing in this section that allows a designer to classify two circuits as one circuit because you choice to run them multi-wire.

 

[hurk27]

Re: Detached Garage

David if you fed your garage with a 240/120 circuit and you used a two pole breaker in the house panel and marked this breaker "Garage" would you consider this as more than one circuit even if it is only a 20 amp circuit it would still be a single circuit. now if we used two single pole breakers in the house panel then some could argue that it is two circuits. but a ground rod at the garage will not make much differance as for lightning protection whether it is a single or two circuits, and this is the only purpose of a ground rod. if a ground rod will add to the protection of two or more circuits then it will also protect just one circuit but I dont see where lightning will look first to see if this garage has one or two circuits before it hits. the damage will still be done. and the other thing is that if you install a ground rod at the garage then you are required to bond it with a #6 back to the main GE so now we have to run a #6 with our garage feed to comply with the NEC if we do install a ground rod.

 

[david]

Re: Detached Garage

Wayne
Branch circuits are classified in art 100, so you are never just installing a generic branch circuit you are designing an appliance branch circuit or an individual branch circuit or a multi-wire branch circuit.

In the case of the garage you are installing a general- purpose multi-wire branch circuit.

You could have a single branch circuit, appliance, individual, & general-purpose, You can not classify a multi-wire branch circuit as a single branch circuit.

It is up to the designer weather to use two single- pole breakers, two single pole breakers with handle ties or a double pole breaker to protect multi wire circuit.

 

[david]

Re: Detached Garage

Wayne

?and the other thing is that if you install a ground rod at the garage then you are required to bond it with a #6 back to the main GE so now we have to run a #6 with our garage feed to comply with the NEC if we do install a ground rod.?

Please explain what you mean
TY
David

 

[jxofaltrds]

Re: Detached Garage

George

Yes you may. In your application you must install a ground rod since the breaker is in the detached building.

If you install the breaker only in the house you do not need a ground rod. In this application you would run the circuit to a junction box then split this single circuit in half.

Thanxs Don. I would not have allowed this before your explaination.

Mike P.

 

[tom baker]

Re: Detached Garage

Curt, In Washington State our electrical inspection agency allows a multiwire branch circuit to be run as a single branch circuit to a seperate building or sturcture. Thats the way Mike Holt explains it as well.

 

[tom baker]

Re: Detached Garage

Curt, In Washington State our electrical inspection agency allows a multiwire branch circuit to be run as a single branch circuit to a seperate building or sturcture. Thats the way Mike Holt explains it as well.

 

[curt swartz]

Re: Detached Garage

Tom & Don,

I understand your opinion on this but I could still see it ending up in a stand off with many inspectors especially with 2 single pole breakers. I will try to remember to ask this question to a few electrical inspectors to see what they say. It still doesn't make sense to me that if you run two 2-wire circuits you need to install a grounding electrode system but if you install one 3-wire circuit a grounding electrode system is not necessary.


Wayne,

The grounding electrode conductor for the separate building is only required to be connected to the equipment ground at the disconnect for the separate building. I don't see where its required to increase the size of the equipment ground conductor between the 2 buildings to the same size as the grounding electrode conductor.

 

[curt swartz]

Re: Detached Garage

Tom & Don

I just had another thought. Lets say we feed a garage with a 3-wire multiwire circuit and use a 2-pole switch as the disconnect. Now from the switch we run two 2-wire cables (one for each circuit) to feed the various loads. Do you still consider the two 2-wire cables one circuit?

 

[don_resqcapt19]

Re: Detached Garage

Curt,
When you split the multiwire branch circuit it does become two circuits, but as long as you split it in the garage, only a single circuit feeds the garage and the exception to 250.32(A) still applies. One of the keys here is OCPDs. If there are OCPDs in the garage, then the circuit feeding the garage is a feeder and not a brach circuit. A feeder circuit to a second building always requires a grounding electrode system at the second building.
Don

 

[curt swartz]

Re: Detached Garage

Don,

I haven't looked at 250.32 when making any of my posts but should have before making my last post. I was think that it was the number of circuits in the building but its the number of circuits that supply the building so if the so if the multiwire circuit before the switch is accepted one circuit the two 2-wire cables after the disconnect switch would be acceptable.

 

[dana1028]

Re: Detached Garage

Curt -
(1999) 225-30 - Outside Branch Ckts - More than One Bldg. - "For the purpose of this section (i.e. feeding a 2nd building with branch circuits), a multiwire branch circuit shall be considered a single circuit.....

and I don't see anything under 240-20 requiring handle ties (should you opt for two single breakers).