Underground wiring through 1-1/2" PVC Conduit

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  #1  
Old 09-21-14, 02:08 PM
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Underground wiring through 1-1/2" PVC Conduit

I have two related questions

1. Im running electrical about 25 in underground 1-1/2 PVC conduit to a water feature. Posted at this link

electrical - Can I use indoor Romex in buried outdoor conduit? - Home Improvement Stack Exchange

I found this information:

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National Electrical Code 2011
2. ARTICLE 310 Conductors for General Wiring
3. II. Installation
4. 310.10 Uses Permitted. These conductors shall be permitted for use in any of the wiring methods recognized in Chapter 3 and as specified in their respective tables or as permitted elsewhere in this Code.
C) Wet Locations. Insulated conductors and cables used in wet locations shall comply with one of the following:
(1) Be moisture-impervious metal-sheathed
(2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2, XHHW, XHHW-2, ZW
(3) Be of a type listed for use in wet locations

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My plan is to run two separate 14 gauge THWN wires for positive and neutral.

My first question is what should I run for the ground? My guess is I should run another insulated THWN wire? Or should I run a bare wire?

2. My second question is what I should do about improper underground wiring that goes to my garage. (I learned it is improper based on the above research.) The underground run is about 50 and is 1-1/2 PVC conduit with one 14-2 UF cable powering electrical outlets and one 14-3 NM-B cable powering lights. The heaviest draw from outlets would be periodic use of a miter saw.

If the worst that can happen is the wires short underground and blow the circuit breaker, Id be inclined to do nothing until that happens. On the other hand, if the improper wiring could result in injury or fire, Id redo the wiring now.

Please advise.

Thanks in advance for your help.
 
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Old 09-21-14, 02:39 PM
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You should run a insulated green wire for your ground. FYI - there is no "positive" in AC wiring.

The requirement of using wet rated cable/wire did not go into effect until 2008 code cycle so that part of your installation may have been OK. However, the fact you have more than one feed to your garage is not correct unless the only lights are for a three way system between the house and garage. You may only have one feed to a separate building.

I would recommend pulling in a new larger feeder to power your garage using the existing cable(s) as a pull wire.
 
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Old 09-21-14, 04:18 PM
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After thinking some more, I recall that the garage wiring is more complicated. The 14-3 powers only the garage exterior light, and the third wire facilitates a 3-way that allows me to switch it on and off from my back porch. The 14-2 UF powers both the interior garage lights and the garage outlets.

Why can there be only one power feed to the garage? Is it a safety issue? I assume that if you want more than one circuit in the garage, you have to run a large gauge wire that powers all the circuits. Is that right?

In any case, Im not inclined to do anything unless the current wiring raises the risk of fire or injury. Does it? If so, what scenarios would lead to fire or injury?

Thanks.
 
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Old 09-21-14, 04:28 PM
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If the 14/3 is for the 3-way then that is allowed. I would expect the installation if the NM cable to be grandfathered in.

The reason you are only allowed one feed is safety. A person could shut off the feeder disconnect thinking there is only one and get killed because there is another feed. This applies to all electrical installations (houses, garages, commercial buildings, sky scrapers, etc., with some special exceptions.
 
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Old 09-21-14, 05:01 PM
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That makes sense.

So there is no special safety issue with the possibility that two hot wires come into contact?
 
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Old 09-21-14, 07:39 PM
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Not sure if I understand the question. Are you asking in the pipe under ground, or with the two feeds to a separate building?
 
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Old 09-21-14, 11:44 PM
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Multiple feeds to a building create a safety hazard as it requires multiple actions to turn off the power.

The NM underground was never allowed AFAIK. The wording was changed to make it more clear.
 
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Old 09-23-14, 04:30 PM
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The NM underground was never allowed AFAIK
Even when installed in conduit? I thought they changed conduit outside to be a wet location. That was why you could not use NM a pipe outside anymore.
 
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Old 09-23-14, 06:22 PM
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I know the wording used to be different. I would need to pull out the old books. I think some were using NM outside but that was against the intent.
 
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Old 09-23-14, 07:27 PM
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Even when installed in conduit? I thought they changed conduit outside to be a wet location. That was why you could not use NM a pipe outside anymore.
In this thread I believe the key is underground conduit. Underground conduit has been a wet location as long as I can remember.
 
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