3-way circuit to a shed sub-panel?

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  #1  
Old 06-28-14, 05:36 PM
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3-way circuit to a shed sub-panel?

I understand that I have to have a disconnect for circuits in a separate building. Can a disconnect be a 3-way switch?

I want to wire a shed with some devices that I can control from the house or at the shed. Can I install a 3-way switch after the 30A DP breaker in the house and travelers for one of the feeds and then another 3-way before the sub-panel in the shed? I think this would require 5x #10 conductors.

How far down would I have to bury PVC conduit for this run?

Is there a lubricant than can help in pulling wire through PVC?

Thanks for your help.
 
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  #2  
Old 06-28-14, 07:27 PM
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I want to wire a shed with some devices that I can control from the house or at the shed. Can I install a 3-way switch after the 30A DP breaker in the house and travelers for one of the feeds and then another 3-way before the sub-panel in the shed? I think this would require 5x #10 conductors.
Branch lighting circuits are either 15 amp or 20 amp. Your 3-way switch wiring should be separate from the subpanel feeder. I would power the 3-way circuit from the new subpanel in the shed. Use a 30 amp 2-pole switch for the disconnect for the 30 amp subpanel feeder.

How far down would I have to bury PVC conduit for this run?
The PVC conduit needs 18 inches of cover.

Is there a lubricant than can help in pulling wire through PVC?
Yes, it's called wire pulling lubricant. You can buy it at any big box store.
 
  #3  
Old 06-28-14, 08:07 PM
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Usually the disconnect is provided by either using a main breaker panel (the main breaker is used as the disconnect) or by adding a back fed breaker to a main lug panel (but only if a breaker hold down is available). Six circuits or less* no disconnect is needed.

*What constitutes six circuits is open to interpretation. Some say space for no more then six breakers in the panel, others say only six breakers installed meets the requirement even if the panel can hold more.
 

Last edited by ray2047; 06-29-14 at 09:33 AM.
  #4  
Old 06-28-14, 08:22 PM
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Thanks CasualJoe.

I am going to use a 15A and a 20A breaker on each phase in the sub-panel in the shed. So there will be four circuits in the shed. The 3-way arrangement is so that I don't have to go back to the house in order to turn on any or all devices on both circuits on the "3-way" phase.

Are you suggesting that I run one sub-panel circuit hot back to a 3-way in the house, then run two travelers back to a 3-way in the garage? This would only give me house-or-shed control of devices on one circuit in the shed, plus I would need to run three additional wires.

What am I missing?
 
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Old 06-28-14, 09:45 PM
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What am I missing?
The subpanel can't be on a 3-way. Only the individual circuits can be 3-ways. Perhaps you can use X-10 switches for those.
 

Last edited by ray2047; 06-28-14 at 10:02 PM.
  #6  
Old 06-29-14, 07:53 AM
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The 3-way arrangement is so that I don't have to go back to the house in order to turn on any or all devices on both circuits on the "3-way" phase.
What am I missing? You wanted a subpanel in the shed, the power should be on all the time. Why would you ever need to go back to the house to turn on any devices? Maybe you don't need a subpanel at all and just need a multiwire branch circuit which would be two circuits sharing a common neutral and common ground. IF some of those devices are to be controlled from either shed or house, you could do as I said and power a 3-way circuit from one of the shed circuits and run your 3-wires + grd (travellers, neutral and ground) in another conduit back to the house switch location.
 
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Old 06-29-14, 08:01 AM
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or by adding a back fed breaker to a main lug panel.
I also thought about that, but I ran into a minor complication a while back using a low amperage backfed main in a subpanel. The Cutler-Hammer BR series loadcenter has become pretty popular as a small subpanel and as far as I know, the BR series 2-pole breakers work well, but there is no hold down kit available for breakers smaller than 60 amp, as far as I know. 60 amp and above BR 2-pole breakers have a hole for the hold down kit screw to actually bolt them into place, but the breakers less than 60 amps do not have that hole.

Other brands may work, but I don't believe the BR from Cutler-Hammer would work in the OP's case.
 
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Old 06-29-14, 08:20 AM
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I would like to have house or shed control for yard lighting and/or for an irrigation pump. I'd also like to have always-on power for working in the shed.

Re 3-way switches and underground wiring, I found a 2008 NEC and have been reading Articles 225 and 300. Would the exception under 225.36 (below) apply to my situation with a shed?

225.30 Number of Supplies. Where more than one building
or other structure is on the same property and under single
management, each additional building or other structure that
is served by a branch circuit or feeder on the load side of the
service disconnecting means shall be supplied by only one
feeder or branch circuit unless permitted in 225.30(A)
through (E). For the purpose of this section, a multiwire
branch circuit shall be considered a single circuit.

225.31 Disconnecting Means. Means shall be provided
for disconnecting all ungrounded conductors that supply or
pass through the building or structure.

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.

My "Disconnecting Means" would be the four-breaker panel plus the 3-way -- for a total of five handing motions to assure all power is off in the shed. I am a novice when it comes to the NEC, but this seems like it would be allowed. What am I mis-interpreting or overlooking?

Thanks for your patience.

Also, if I am reading Table 300.5 correctly for Column 3, I only need to bury the PVC 18". Is this correct?

Thanks again.
 
  #9  
Old 06-29-14, 09:32 AM
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The branch circuits may have 3-way circuits as I said above in post #5. You keep writing about putting the service disconnect on a 3-way. That can not be a 3-way.
 
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Old 06-29-14, 09:36 AM
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Joe wrote:
there is no hold down kit available for breakers smaller than 60 amp
Thanks. Edited my post.
 
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Old 06-29-14, 12:40 PM
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Joe wrote:



there is no hold down kit available for breakers smaller than 60 amp

Thanks. Edited my post.
Ray, that only applys to the Cutler-Hammer BR series as far as I know. I know that Square D Homeline does have a hold down kit for breakers as small as 50 amp, and probably smaller, and assume Siemens does too.
 
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Old 06-29-14, 12:47 PM
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each additional building or other structure that
is served by a branch circuit or feeder on the load side of the
service disconnecting means shall be supplied by only one
feeder or branch circuit
You want the subpanel and that is a feeder serving the structure. In my opinion, adding a 3-way circuit fed from the subpanel with a 3-way switch at the house would not constitute a branch circuit serving the house from the shed, it's just a switch loop.
 
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