Running electrical conduit on exterior of home


Old 06-08-05, 11:50 PM
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Running electrical conduit on exterior of home

I've already wired something and I wanted to run it by folks here to see if I've done something bad.

I had an exterior flood light with motion sensor located in a bad place. (Too low to the ground and could be tampered with.) So I wanted to re-locate it to a higher location on the house. At the same time, I wanted to add another motion sensor flood around the corner of the house to improve security.

The original flood light was attached to a surface-mounted exterior-grade metal box. 14-2 NM cable came from a switch inside the house through the wall into the box through the back.

So to relocate the light and add the new one, I needed to run conduit to the new locations and terminate the runs with new watertight boxes. Each new light location is about 10 feet away from the original location in opposite directions. I chose to run 1/2" plastic grey conduit. Due to the asthetics of the exterior run, it was best to run one conduit from the original light location about 2 feet to a certain location and then tee off in two opposite directions to get to the new locations. The ends of the conduit have threads on them which are screwed into the watertight boxes and sealed with silicone caulk.

Now we get to the part where my reading this website makes me wonder if I've done something bad. My choice for running wire in the 1/2" conduit was 12-2 UF. I knew that I couldn't run NM on the exterior of the house because of moisture. I've read in some postings here that UF shouldn't be run in conduit. Have I done something bad?

Yes, it was somewhat of a pain to use 12-2 UF with the 1/2" conduit... especially when I had to run two of them through the final two foot section from the tee down to the original outlet box where the wire nuts are.... (I had to strip the sheathing and run just the insulated wires themselves through the conduit at that point.) Do I have a fire hazzard on my hands here? I don't want to do anything unsafe... but, I wouldn't think 360W (90W * 2 fixtures * 2 floods per fixture) through a pair of 12-2 runs without sheathing in a two foot section of 1/2" conduit would generate that much heat.

Can someone either put me at ease or sound the alarm for me to re-wire it?
Old 06-09-05, 07:53 AM
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Well there is no imminent danger of fire; but your installation does not meet the elect. code. Sheathed cable is not to be run inside conduit. You did the right thing on that section where you just ran the unsheathed conductors, but may have too many conductors in 1/2" conduit.

If it was my house, I would probably leave it alone, understanding that at the time of a future sale, an inspector may notice this and require a change. Also, if permits are required for electrical work ( they are in most places ) then if you try to get a permit now, you will face (a) a late fee and (b) rejection by the inspector.
Old 06-09-05, 08:58 AM
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In my opinion, running UF through conduit is okay. The arguments against it always point to specific wording in the code, and that wording has now been removed in the new 2005 code.

However, stripping the sheathing off UF and using the individual wires inside is not really allowed, since the individual wires inside are officially unrated.

Furthermore, it is almost certain that you violated the fill rules for the conduit.

Nevertheless, I agree with 594 in that the violations are not serious enough that I would redo it. Just use the information to do better next time.
Old 06-09-05, 03:09 PM
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Let's say, for example, that I did want to do this over again. What should I change?

Instead of 12-2 UF, what should I use? I'm not familiar with anything other than Romex with sheathing.

The circuit has 14-2 NB running into the box. Could I go with a 14 guage exterior grade wire in the conduit without needing to change any of the conduit? (Someone said I was not to code with four 12 guage and two ground in a 1/2" conduit.) The 1/2" tee that I'm using isn't big enough to do splicing in it so I need to run all the conductors down to the original box.
Old 06-09-05, 03:14 PM
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You could use 14 gauge THWN individual conductors. You'll find that almost all THHN rated wire is dual-rated THWN. All of the big box stores sell it on spools or by the foot.
Old 06-09-05, 06:42 PM
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You are allowed 8 #12 THHN or THWN in 1/2" PVC schedule 40 conduit, I'm pretty sure that is the pipe you have.

If the circuit is protected by a 15 amp breaker you can use #14 and would be allowed 11 THHN or THWN in the 1/2" pipe.

You don't want to run that many because it would be a pain to pull it but technically based on the NEC that is what your allowed, also when you run that many in one pipe you have to derate the wire ( meaning a wire that normally holds 15 amps would now be 8 amps etc.) In your case it doesn't really need to be considered since your load is only 3 amps(360W)

Use the THWN if you have a choice ( the W means wet location) but like ibpooks said in his post, most wire is dual rated THHN or THWN.

You will need to run black wire, a white wire and a green for ground.

Now with that said, if it were me.. I would leave what you have since there is no serious safety issue and is doubtful that the average home inspector would even catch it unless he has some electrical backround.

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