Running one 12/3 UF-B from panel to shed as a split circuit

[remagenman]

So, I want to power the shed from the main panel using one 12/3 UF-B cable but as 2 circuits and this is what I've learned so far:

-you can only run 1 12/3 cable to shed from panel (panel is about 25 feet away).
-I can do a dual circuit with the one cable by doing a MWBC using a 20A 2-pole breaker.
-I will only run some LED shop lights, radio (on most time) with the occasional band saw, table saw, planer, all 115V (occasionally). I will probably run a Shop-Vac while running one of the tools with the lights and radio on.

Is this setup good? I already setup 220V outlets for whatever needs to be ran 220V outside the garage so I dont need 220V in the shed.

Thanks. Here is a picture of what I want to run as a MWBC.

 

[sberry]

Looks dandy. There are a couple ways to do it, can use a double pole switch as a disconnect and the breakers in the main suffice.

 

[ripperd]

Just make sure you don't use a tandem circuit breaker. The shared neutral only works if the two circuits are on different hot legs via handle tied regular breakers.

 

[remagenman]

Thanks for the feedback, pointing out crucial steps helps for sure. It will give me more Google questions to get this right.

 

[7635tools]

I wouldn’t waste my time with UF cable. I would run conduit out to the shed. You have to dig a trench either way, so why not put it in conduit. At least that way when the underground goes bad you’re not digging it up again.


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[sberry]

Yup, but, I personally am not scared of a little digging and would rather have the gfci local. If I am going above and beyond I run a larger wire to a 6 space but again it's more than needed and even lots of welding can be done 120v and or 30A service today. Used to be if you wanted to run a buzzer and also wanted 120/ had to run 6 wire and it drove the cost up or we used 2 alum.
A Maxstar and some of the other new machines will run a 1/8 lo hy on 20A/240 and they run 3/32 lo hy and 1/8 6011 on 120v past 100 ft without tripping the breaker.

 

[toplessHO]

What's your burial plan? Others don't like this but if you use a GFCI breaker you only need 12" depth.

only if its a single 120v circuit

 

[Stuff]

only if its a single 120v circuit

Yeah, people have corrected me before. Keep on thinking code says 120v to ground.

 

[JeepJohn62]

Your diagram looks good and it should work fine. Keep an eye on the neutral for signs of discoloring from heat.

I have never liked shared neutrals for shop loads. The electrical motor loads cause the currents to be out of phase and can potentially overload the neutral. The cost of running a dedicated neutral is not expensive.


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[AntonLargiader]

From some old notes of mine, any detached building with electrical power must have:

• a means of disconnect at point of entry, can be indoors or out (225 Part II)
• a receptacle (210.52 G)
• GFCI protection for all receptacles (210.8)

There are further requirements for garages like exterior door light and so forth but I assume that doesn't apply here.

 

[teamextreme]

YThe electrical motor loads cause the currents to be out of phase and can potentially overload the neutral.

Huh? Care to elaborate on this? How does a motor load cause the neutral to be out of phase and overload it?

 

[sberry]

With my own might pipe but normally use cable for this kind of thing and for diy types it's so much easier, get piece of wire the right length and get it done.

 

[theoldwizard1]

... can use a double pole switch as a disconnect ...

While that might be useful, I don't understand why any switches, let alone a double pole switch is required. What if one circuit was lights and the other outlets ?

 

[sberry]

Any structure is required to have disconnecting means, it can be a switch or breakers but it must disconnect all ungrounded conductors. If it's a multi wire it needs to be 2 pole. You add light switches after.

 

[JeepJohn62]

Huh? Care to elaborate on this? How does a motor load cause the neutral to be out of phase and overload it?

Hi. The two 120V feeds are 180 degrees out of phase from each other. Therefore they will be 120V to neutral, but 240V to each other.
The current flow on the neutral is also 180 degrees out of phase, which effectively cancels each other out. This is why you can run a shared neutral.
However, the current in a motor load is inductive, so the currents DO NOT cancel in the same manner, and can become additive.
This can overload the neutral in this case.


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[theoldwizard1]

Any structure is required to have disconnecting means, it can be a switch or breakers but it must disconnect all ungrounded conductors.

I thought that was only on more than 6 circuits ?

Lots of garages have an outlet that is "hot at all times".

 

[AntonLargiader]

The text in 225 seems to stand independently of that stuff. 225.31 says you need a means of disconnect, and .32 basically says as close as practical to where the conductors enter.

I know what you mean about detached garages with always-hot receps. Our house had that when we bought it, although it definitely did not look like a to-code installation. Maybe it's a relatively recent (last few decades) requirement?

Code aside, it sure seems like a good idea to me.

 

[sberry]

I thought that was only on more than 6 circuits ?

Lots of garages have an outlet that is "hot at all times".

More than 6 need a main,.
While lots of them don't have it there is sposed to be means to disconnect all ungrounded conductors.

 

[alfredeneuman]

To elaborate further, it's 6 throws of the handle.
If you have only 2 pole breakers 6 of them meets the rule.

If you have 3 2 poles, then you can only have 3 single poles without breaking the rule.

 

[75gmck25]

How about using one of these at the garage to provide a shutoff and also break out the 12/3 into two 120 volt circuits? https://www.homedepot.com/p/Square-...door-Main-Lug-Load-Center-QO2L30SCP/100157760

Bruce