two feeds to detached garage

[willlgord]

I have a 100 amp breaker feeding the garage from the house and always shut off the main when I leave the building. I'd like to have one separate circuit for outside lights on motion detectors and the garage door opener. This would be 20amps run through a second underground conduit. I've read that it's against code to run two circuits to an outbuilding unless both can be cut off with one breaker, has anyone encountered this before?

 

[Zeke]

Nothing to encounter. The NEC states that only one feed to any outbuilding. What you can do is put in a master switch to kill all the circuits but the one you need for lights and opener. You will probably need to make your existing panel a subpanel and put that single circuit in a new panel fed by the main at the house. Or vise versa, which ever is easier.

Now, the real electricians here will probably have a better idea.

 

[matt_i]

I am curious why the main has to be shut down. This is atypical with a guess of 500 million residences and business locations in the USA continuously electrified (iow mains are always on minus maintenance or repair work)

 

[wyliesdiesels]

I have a 100 amp breaker feeding the garage from the house and always shut off the main when I leave the building. I'd like to have one separate circuit for outside lights on motion detectors and the garage door opener. This would be 20amps run through a second underground conduit. I've read that it's against code to run two circuits to an outbuilding unless both can be cut off with one breaker, has anyone encountered this before?

Why are u shutting off the main?

Do U realize u can wear out the breaker over time by doing this.

 

[teamextreme]

I agree with ^these guys. You are using the main as a switch, which unless is has a "SWD" marking on it, it's not rated for. You are causing unnecessary wear on the main. I would re-wire your space accordingly to provide actual switches to de-energize that which needs to be without throwing the main. Then you can power your motion lights from the panel without issue.

 

[willlgord]

I know there would be extra wear and tear on the breaker....I wonder how many on-off cycles they are rated for? I'm just being overly cautious I suppose, I have way too many circuits in the garage to switch them all. I'll just leave the main on.

 

[alfredeneuman]

You are using the main as a switch, which unless is has a "SWD" marking on it, it's not rated for.

An "SWD" marking on a circuit breaker merely means that it's rated for use as a switch for fluorescent lights, nothing more.

 

[BreeStephany]

If you wanted a solution to kill all power to your shop with leaving a lighting load, you could install a 100amp service disconnect that has 4 places for breakers (2 pole 50A & 2 pole 100a) where power comes into the outbuilding, then come off of that disconnect with a 50a panel for lighting, contactor control circuit load and exterior loads that you don't want to shut off (exterior plugs, etc.) and then put a 100a contactor after the breaker but before your 100a panel, that way you can switch your 100a panel with a switch, thus preventing unnecessary wear on your 100a main breaker.

With that said, is it a cheap solution? DEFINITELY NOT. Will it do what you want to accomplish while being in code, absolutely. Is it overkill? probably

Depending on the loads you absolutely want to kill, you could also do a load calc and install an appropriately rated subpanel off your current panel, put it on a contactor and separate out the loads from your current panel to your subpanel. This would likely be a much cheaper solution because a 100A contactor is NOT cheap, where as a 50A contactor might actually be within your price range.

 

[Zeke]

An "SWD" marking on a circuit breaker merely means that it's rated for use as a switch for fluorescent lights, nothing more.

I've seen many other types of warehouse lighting on switch rated breakers. All wired to code.

 

[rlitman]

I know there would be extra wear and tear on the breaker....I wonder how many on-off cycles they are rated for?...

Less than you'd think. The big breakers at my work actually have counters, but even the smaller stuff often has counts documented. Commonly, on breakers, I'd expect around 1000 actuations under load, and somewhere between 2-10 times that with no load.

UL 1008 (the guideline for transfer switches) requires the ability to switch at least 6000 times, but only 1000 of those are done under load.

 

[ishiboo]

They'll only last 10 years switched daily under small load, at which point you may have to exercise the lifetime warranty.

If you really have to do this, put a main in the garage with two breakers - one feeding your existing panel and another for lighting/etc. loads. Put a 100A contactor in between that you can control however you want. You could put the garage lights on the constant power side and even switch the whole 100A sub off the light switch.

Or you could ignore the MINOR phantom power consumers and just make sure you shut off the big stuff when you leave.

 

[Crazyjake8493]

I've seen many other types of warehouse lighting on switch rated breakers. All wired to code.

An "SWD" label means it's rated for switching fluorescent light loads, and an "HID" label means it is rated for switching high intensity discharge lighting loads, as well as fluorescent lights.

 

[SiGmA_X]

I personally think it is rather silly that the NEC disallows having a 3 way lighting circuit to an outbuilding in addition to a main feed. However, being that is the case, I would consider a wireless switch or a timer or light sensor, and run it from the house.

 

[pattenp]

I personally think it is rather silly that the NEC disallows having a 3 way lighting circuit to an outbuilding in addition to a main feed. However, being that is the case, I would consider a wireless switch or a timer or light sensor, and run it from the house.

You can have a 3 way switch circuit from the garage to the house. It's fine if the power source for the garage lights being switched is from the garage. Just can't have the power source for the switched garage lights coming from the house.

 

[Zeke]

An "SWD" label means it's rated for switching fluorescent light loads, and an "HID" label means it is rated for switching high intensity discharge lighting loads, as well as fluorescent lights.

Gotcha. Thanks.