two circuits in a ring configuration

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  #1  
Old 04-27-06, 03:22 PM
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two circuits in a ring configuration

Right now I've got a "V" configuration, where my house & load center are at the bottom of the V. My garage is at the end of the left tine, and my pond is at the end of the right tine. Each is a 20A circuit with its own grounded neutral.

Now my project coming up this summer is wiring pump controls into the garage. This was not part of the original plan but it now makes the most sense. I put in underground conduit across the top of the V to accommodate this but now I am concerned about meeting code regarding multiwire vs. subpanel in the garage, since the garage would now have two circuits fed in from opposite directions.

So if I just make sure the garage is on the A bus and the pond is on the B bus, thereby creating a multiwire, would it matter that it was fed from two separate directions? Except for grounding, I could keep the circuits separate in the garage but I'd like them to share conduit for efficiency.

I could also abandon the current pond feed (12/3 UF direct buried with the red wire switched in the house) so it would look like an upside down L, with the house at the bottom, the garage at the junction, and the pond at the outside edge. Then I would have a multiwire to the garage in 3/4" rigid and one 20A circuit continuing to the pond in Sch 80 PVC. But that seems like a waste of copper to abandon my 12/3 UF.
 

Last edited by ArgMeMatey; 04-27-06 at 05:03 PM.
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  #2  
Old 04-27-06, 04:07 PM
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balanced current

You may have an issue with current balance in that multiwire. That is, the hot and return paths may not reside in the same raceway/conduit. That would be a big issue with steel EMT/boxes and not a good practice with any raceway.
 
  #3  
Old 04-27-06, 04:56 PM
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You are only allowed one circuit to an outbuilding. That circuit can be a multi wire circuit, but it must be one circuit. However, your proposal to feed from two different locations on opposite legs of your 240 volts is NOT a multi wire circuit. It is only two circuits, and is not allowed.

The proper solution is to abandon your existing circuits and run a proper circuit to the garage to handle all your needs. This most likely means a sub panel in the garage.
 
  #4  
Old 04-27-06, 05:09 PM
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Originally Posted by ArgMeMatey
Each is a 20A circuit with its own grounded neutral.
Are you saying that you have neutral and ground bonded in the garage?


> Now my project coming up this summer is wiring pump controls into the garage.
What "controls"?


> I put in underground conduit across the top of the Y to accommodate this
> but now I am concerned about meeting code regarding multiwire
> vs. subpanel in the garage, since the garage would now have two circuits
> fed in from opposite directions.

Are you just controlling the pump or are you using electricity from the pump circuit?


> So if I just make sure the garage is on the A bus and the pond is on the B bus,
> thereby creating a multiwire,
> would it matter that it was fed from two separate directions?

Whether the installation is safe, legal, or functional has nothing to do with what pole is used for hot.


> Except for grounding, I could keep the circuits separate in the garage
> but I'd like them to share conduit for efficiency.

What circuit is sharing with this? I thought you put in a new conduit.


> so it would look like an upside down L,

I don't know what matters, L, Y, V, T, D, or G, upside-down, sideways, or mirror reversal.
Post a drawing or something if it matters.

Just name the start points, endpoints, distance, what circuits you have, and what you want to do.


> Then I would have a multiwire to the garage in 3/4" rigid and one 20A circuit continuing to the pond
> in Sch 80 PVC. But that seems like a waste of copper to abandon my 12/3 UF.

It sounds like you want to be in the garage and able to control the pump circuit at the house but made no provision for a low voltage control line. The pond is near the garage, but there is no way to control the pump from anywhere except the house.

Is this correct?
 

Last edited by bolide; 04-27-06 at 05:32 PM.
  #5  
Old 04-27-06, 07:16 PM
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Thanks for your response.

Originally Posted by bolide
Are you saying that you have neutral and ground bonded in the garage?
No. Let's just say neutral. I was saying grounded neutral as opposed to ungrounded hot. The neutral is only grounded at the load center.


Originally Posted by bolide
What "controls"?
Nothing fancy: Standard lighting toggle switches.


Originally Posted by bolide

Are you just controlling the pump or are you using electricity from the pump circuit?
Timer would use electricity, but if that's a problem I could just continue to use the timer in the house.

I just want to put switches in the garage to control receps at the pond so I don't have to open my valve box everytime. My pond has:

1. 45W fountain pump,
2. 150W bottom pump,
3. 115W skimmer pump,
4. 15W UV filter
5. A small lighting transformer.

The lighting transformer is outdoor rated so I'd just hang it by the pond and put it on the same switch with the fountain pump. If I leave the timer in the house, I would then have just four switch loops coming from the garage, so the wires in the now-empty conduit would be:

1, 2, 3, 4: switched hots
5. Hot from circuit breaker in house
6. Hot from timer in house
7. Ground

Originally Posted by bolide

Whether the installation is safe, legal, or functional has nothing to do with what pole is used for hot.
Maybe I don't understand a multiwire then. I thought a multiwire was for example a black wire on pole A, a red wire on pole B, and a neutral. Haven't I read here that you can have a multiwire in the garage? I thought that could mean two circuits, meaning two breakers on opposite poles.

Originally Posted by bolide

What circuit is sharing with this? I thought you put in a new conduit.
Sorry. I mean I have to use conduit in the garage and from the spot where the switches would be, I would also like to have an outlet and a switch for a light on the back of the garage.

So in addition to the 7 wires coming from the pond circuit, the new conduit in the garage would have three more wires from the garage circuit:
8. Hot
9. Neutral
10. Switched hot for light at south wall outside garage.

Originally Posted by bolide
Post a drawing or something if it matters.

Just name the start points, endpoints, distance, what circuits you have, and what you want to do.
Pond circuit A-B 60', B-C 25'.
A = House, starting point
B = Pond, midpoint,
C = Garage south wall endpoint, desired outside light location
Timer controls fountain pump and underwater lights.
Two other pumps and UV run 24/7 except maintenance.

Garage circuit, C-D 20', D-E 30'
D = Garage north wall endpoint, desired switch location
E = House, starting point

Right now I have empty conduit between B and C.
I want to add conduit in the garage between C and D.
The switch loops would run in the C-D conduit, and so would the new garage light feed.

Originally Posted by bolide

It sounds like you want to be in the garage and able to control the pump circuit at the house but made no provision for a low voltage control line. The pond is near the garage, but there is no way to control the pump from anywhere except the house.

Is this correct?
Yes, I want to control the pumps from the garage.

I have plenty of low-voltage conduit in place, but I don't have any low-voltage control circuits like you'd have for a sprinkler system.

Currently, I can only control the fountain and lighting from the timer in the house. I control the other pumps by unplugging them at the pond.
 
  #6  
Old 04-27-06, 07:38 PM
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You have numerous issues here, and numerous points that you need to understand. I am not going to attempt to address all of them. I am simply going to address the issue of multi-wire circuits.

A multi-wire circuit is simply multiple ungrounded conductors (hots) from different supply legs all sharing the same grounded conductor (neutral). You can take one 20A circuit from leg A, and one 20A circuit from leg B, run both hots on 12ga conductors, and share a single 12ga neutral.

A separate issue entirely is the issue of keeping all conductors of the same circuit together. This means that if current flows out on an ungrounded conductor in one conduit or cable, you want it flowing back on a grounded conductor is the _same_ conduit or cable. I should note that this is a code _requirement_ for conductors in metallic wiring methods (eg. metal conduit), but simply _good design practise_ for non-metallic wiring methods. All other code issues aside, it is bad design to run the hot conductor to your garage, then have switched hots run to your pond, and finally have the neutral run back to the house via a different conduit.

There are other issues associated with the maximum number of circuits feeding a detached structure, derating for number of conductors in the conduit, wiring methods underground, etc. that I am sure need to be addressed in addition to the above comments.

-Jon
 
  #7  
Old 04-27-06, 08:29 PM
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Originally Posted by winnie
A multi-wire circuit is simply multiple ungrounded conductors (hots) from different supply legs all sharing the same grounded conductor (neutral). You can take one 20A circuit from leg A, and one 20A circuit from leg B, run both hots on 12ga conductors, and share a single 12ga neutral.
Thanks. That is what I thought.

Originally Posted by winnie
A separate issue entirely is the issue of keeping all conductors of the same circuit together. This means that if current flows out on an ungrounded conductor in one conduit or cable, you want it flowing back on a grounded conductor is the _same_ conduit or cable. I should note that this is a code _requirement_ for conductors in metallic wiring methods (eg. metal conduit), but simply _good design practise_ for non-metallic wiring methods.
OK, inductive heating issue, right, good point, what telecom guy said, would apply here since I cannot use PVC or romex in the garage.

All this for switches in the garage? Forget it. I think I'll bite the bullet and add a pedestal by my valve box for switches.

Now I still have that conduit from the pond to the garage. Right now there is just a box screwed into the exterior garage siding with the Sch 80 coming up into the box. Can I put a receptacle in that box with a weatherproof cover, connect it to the pond circuit and have no connection to the existing garage wiring system? In other words, could code consider the garage to be a substitute for a 4x4 post? I'd like an outlet there for convenience.
 
  #8  
Old 04-27-06, 09:24 PM
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> inductive heating issue, right, good point, what telecom guy
> said would apply here

Where is anyone getting inductive heating? It's not in anything that you described.

What telecom guy said was the exact opposite of what he meant.

It's still not apparent how it is relevant.
 
  #9  
Old 04-27-06, 09:27 PM
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Originally Posted by telecom guy
You may have an issue with current balance in that multiwire.
I don't see it.

> That is, the hot and return paths may not reside in the same raceway/conduit.

As far as I am concerned, the supply and return paths must reside in the same raceway/conduit/enclosure.


> That would be a big issue with steel EMT/boxes
if they aren't in the same raceway.

> not a good practice with any raceway.
It is a bad practice to fail to have all relevant conductors in the same raceway.
 
  #10  
Old 04-27-06, 11:48 PM
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Check with you inspector. Ask if your plan would be permitted under section 225.30(D), which allows additional feeders or circuits to a building or structure for uses such as this (the control of outside equipment from other locations).
 
  #11  
Old 04-28-06, 04:06 AM
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ArgMeMatey,

Is there any reason that you are considering or actually planning to _electrically connect_ the circuit being fed from the house directly to the garage with the circuit going to the pond?

If you never electrically connect the two, then you are not creating a multi-wire circuit, and you are not creating a 'current loop'. From your initial questions, it sounds like you were going to do something like take the 'hot' from the garage circuit and use it to feed switched circuits going out to the pond, with the return on the pond neutral. This would be a code violation with metallic wiring methods.

But if you simply run the hot from the pond to your switch location, and run the switched hots back to the pond, then this particular issue simply isn't a problem. You will not have created a multi-wire circuit. Connecting current carrying conductors in a big loop is bad. Connecting the equipment grounding conductors in a ring is not generally considered a problem. There may be other issues with your plan that you need to address.

I've just re-read your initial post. I think that your question about 'multiwire' created quite a bit of confusion. You say in your initial post that the two circuits would be electrically separate, but you also ask about creating a multi-wire. A multi-wire circuit implies that the two circuits share a neutral and are _not_ electrically separate. If the two circuits remain electrically separate, then you will have no problems with supply and return not being in the same conduit. If the two circuits are combined into a multi-wire, then you will have these problems.

-Jon
 
  #12  
Old 04-28-06, 05:03 AM
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Originally Posted by winnie

Is there any reason that you are considering or actually planning to _electrically connect_ the circuit being fed from the house directly to the garage with the circuit going to the pond?

...

I think that your question about 'multiwire' created quite a bit of confusion.

-Jon
No, the two circuits do not need to be electrically connected at all.

I think you're right, the multiwire talk just muddled things up. My thought was that if two circuits appeared in the garage, each would need to be half of a multiwire.

Thanks.
 
  #13  
Old 04-28-06, 05:15 AM
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Originally Posted by ArgMeMatey
I think you're right, the multiwire talk just muddled things up. My thought was that if two circuits appeared in the garage, each would need to be half of a multiwire.
This is a different other issue. There is a general requirement that you only run a _single_ feeder or branch circuit to your garage. This _single_ circuit _may_ be a feeder to a panel, or it _may_ be a multiwire branch circuit. What it may not be _in general_ is two separate individual circuits. (NEC 225.30) It is quite common to run a single multiwire circuit to a garage rather than go to the expense of a full subpanel.

However Juhl pointed out the exception that applies in this case. 225.30(D) explicitly mentions separate circuits for separate uses, and spells out _control of outside lights_ as an example of separate uses.

-Jon
 
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