Oldwork: Garage, No Neutral

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Old 03-12-12, 01:14 AM
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Oldwork: Garage, No Neutral

Hm, I seem to have a situation similar to this: an out building (garage&garage apt) connected to the house via two hot conductors and a grounding conductor feeding a panel there. The hot conductors are protected by a two-pole breaker at the service entrance on the house.

The tricky bit is, the garage panel neutral is bonded there. There is no neutral running back to the house.

I was concerned enough about this that I queried a pro about it (who was out to deal with something else), who confirmed that under the circumstances, it was OK. In fact, he seemed a bit put out that I asked such a nitpicky question.

When he explained the reasoning, it made sense, and I looked it up and confirmed that it was OK, but darned if I can remember what the deal was.

(The conductors are not a cable, but loose in a buried conduit.)
 
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Old 03-12-12, 08:23 AM
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an out building (garage&garage apt) connected to the house via two hot conductors and a grounding conductor feeding a panel there.
Do you have three insulated wires one of which is white* and two that are other then white or green? Older versions of code permitted this under very limited conditions though it is no longer permitted. Newer code does not permit this under any conditions. In your other post in the basement the neutral was a bare wire and that has not been code for several NEC cycles if ever.

*If the wires are larger then #6 a color other then white could be used as neutral if remarked on both ends.
 
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Old 03-12-12, 09:31 AM
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"There is no Neutral running back to the house"---- based on this statement , I advise that you remove the cover from the Service panel and examine the conductors that connect to the 2-pole CB that protects the conductors feeding the garage panel.---- these conductors couild be cable conductors or conductors inside a raceway such a electrical tubing or PVC conduit.

Very un-likely that the cable or raceway enclosing the conductors that connect to the garage CB would contain only the two conductors.
 
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Old 03-12-12, 10:17 AM
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There are two black conductors and one green grounding conductor running from the SE to the garage panel through buried PVC conduit. White neutral in the garage panel bonded to ground there, and I have driven a new grounding electrode at the garage.

I believe, now that you bring it up, that this was grandfathered in. This is out in the county.

Based on comments here, I may well go to the trouble to pull a neutral through the conduit, and un-bond the neutral-ground connection at the sub-panel.

(And thanks for moving this to its own thread. I didn't really expect a response; I was just noting that under some conditions, you might (semi-legitimately) not have a neutral.)
 
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Old 03-12-12, 10:38 AM
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It's distinctly possible that whoever did the wiring had "on hand" a lenth of a conductor with Green insulation that he wanted to use for the Neutral , and was further negligent by not "Identifying" the Neutral as such with White marking tape.

The best procedure would be to pull out the existing conductors ,add a 4th White conductor to the three existing conductors , and re-pull these four conductors thru the PVC raceway. Much depends on the size of the PVC conduit and the size of the existing conductors ; the Green Equiptment Grounding Conductor can be smaller is size than the three current-conductors if it's necessary to reduce the conductor conduit-fill of the PVC conduit in order to pull the conductors thru the conduit.
 
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Old 03-12-12, 11:47 AM
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No, the green conductor is in fact bonded to the grounding buss at the SE and in the subpanel. (Although in the subpanel, the grounding and the neutral buss are bonded together, and neutrals are randomly bonded to either buss. If I run a new neutral conductor, I will of course have to break the bond at the subpanel.)

And thanks for reminding me to evaluate conduit fill before pulling a new neutral conductor.

This is complicated by the pump being feed through a separate 12/3-g cable, not loose conductors, with the neutral unused and capped off at the pump switch. If I pull anything through that conduit, I'll replace the bulky cable with loose conductors.

Given that I have a new ground rod driven at the garage, does that help reduce the size required for the grounding conductor? Under no circumstances do I want to dig up and replace the conduit.

===

I have two people in mind when I approach a wiring project:

The Next Guy, the guy who comes after me. What must I do to not make his life any more difficult than absolutely necessary?

And

The [mumble grumble snarl] Last Guy, who I live in fear of being. I spend more time correcting Last Guy mistakes than I do on the task at hand.
 
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Old 03-12-12, 12:51 PM
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Given that I have a new ground rod driven at the garage, does that help reduce the size required for the grounding conductor?
Apples vs oranges. The ground wire to earth is to provide protection from things like lightning. The ground wire back to the main pane is to provide a low resistance path to clear faults such as a short by tripping the breaker.

Tell us the size of the breaker supplying the subpanel, size of the wires, distance, and size of the conduit and we can give you a better idea of what needs to be done to bring it up to modern code.

P.S. I would be careful of using the electrician who evaluated it for you. It may be he stopped learning code when Edison gave him his license.
 
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Old 03-12-12, 01:29 PM
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What you refer to as the "Grounding Bus" may be the Neutral terminal bar where the Neutral , "White wire" Conductors terminate. There would be no White wires connected to a panel "grounding bus " , only bare or Green conductors.

If the Service panel end of the Green UG conductor terminates on the Neutral terminal bar of the Service panel , and if the sub-panel end of this condutor terminates on the Neutral terminal bar of the sub-panel , it's most likely that a conductor with Green insulation was used as the Neutral conductor.

The size of the required Green Equiptment Grounding Conductor is based on the rating of the circuit-breaker that protects the UG Feeder Conductors between the Service panel and the Sub-panel. If you install this conductor, it must terminate on a Grounding bus in the sub-panel , a connection-point which is competely seperate from the Neutral terminal bar.
 
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Old 03-12-12, 02:53 PM
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The grounding conductor originates in the grounding buss at the SE; only bare and green wires are connected to it. Again, it looks like this was grandfathered in and met code at the time.

Supply is 2 x 80 A breakers.

Grounding conductor is 6 ga stranded; the two hot conductors are unreadable (dark red dot-matrix on black) but look to be a size larger than that, so... 4 ga stranded? As I read Table 310-13 (re-printed in Mullin 13), if it's 75 deg C wire, it has an ampacity of 85 A, so I'm OK there.

Conduit looks to be 1-1/4" and about 50 ft long.

Using this fill calculator, it looks like I have plenty of room for 4 #4 conductors for the garage supply, plus 3 #12 conductors for the pump supply.

Thanks again for the comments; I really didn't mean to go into this much detail. But OK: I would have eventually needed to know it anyway.
 
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