[sparc421]

I have an electrical installation issue that I need help with. I've spent weeks searching for answers. I've asked an electrician and consulted the manufacturer, yet nobody seems to be able to tell me the right way to do it.


It seems simple - how to wire a RAB YBLED26 with mounting arm (YARM24) to an existing roof-mounted pole.


The prior installation left me with a length of 1/2" EMT coming out of the roof:

Now, I'm fairly certain that NM isn't permitted inside EMT. But I'm not too worried about that part right now; the EMT runs into the attic and isn't easily accessible.


This is how I plan to mount the arm. I will have to find the right hardware to clamp it to the pole. I'm showing the EMT going up into the arm - but I don't think that's right. The clamp will probably move up the arm a bit to reduce the moment (force) on the clamp.

I'm now thinking of cutting back the EMT (this will be a challenge) without damaging the NM (using a rotary cutter). That way, I can place a junction box closer to the roof to transition into whatever wiring I use.



If I do this, I see a few options:

1. Use Seal-Tite and run the conduit either a) up the pipe into the junction (but how do I clamp?) or b) parallel to the arm, terminating via a 90 degree clamp into the 1/2 KO on the bottom of the fixture (see the installation drawings). I don't think this will look great (especially option "b").
2. Run another short length of 1/2 EMT up the pipe and a length of THHN to terminate in the junction box. The EMT would run at least 6" up the pipe to prevent any possible access to the wire by hand, but there'd be no clamp at the end of the EMT and the THHN would run in the arm pipe for a length before reaching the junction. This doesn't seem right, though the wire is protected and safe from damage. By the way - regardless I will be filling the bottom of the arm opening to prevent bees from making it a home.
3. Use SJW, SJOOW or equivalent. Use a cable gland with a drip loop from the junction box, up into the pipe. I've seen a similar installation method used on buildings nearby, but my understanding is that code prevents use of flexible cable like this for any type of permanent installation.

As you can see, I've thought about this way too much...


One last photo of the prior installation to give some additional perspective:

 

[sparc421]

I can't post the link, so here's a capture of a portion of the installation sheet:

 

[seharper]

Now, I'm fairly certain that NM isn't permitted inside EMT. But I'm not too worried about that part right now; the EMT runs into the attic and isn't easily accessible.

NM-B isn't permitted outdoors, either! Look at it. It's roached good-n-plenty, and water has been going down that pipe and ruining any other NM in it. Probably filled the junction box with water and ruined the NM heading into the house. Amateurs!

Yeah, that's gotta go. Since UF-B is not allowed inside 1/2" EMT, that narrows you down to THHN individual wires. Which means you will need to have all conduit to an appropriate indoor-outdoor transition point, and then run THHN - pardon me, THwN (it will be dual-listed) from that point up to the lamp. This may be unfamiliar to you, but it's about to become your new favorite wiring method. Select stranded THWN wire; if you're unsure on size get 12 AWG.

"Oh noes, but 12 AWG is so stiff and hard to work with" STRANDED wire my friend, like I say, once you've had THWN stranded, you'll never go back

The only annoyance of stranded wire is it's difficult to put on screws and illegal to put in backstabs. You won't have that problem here; you'll be wire-nutting!

This is how I plan to mount the arm. I will have to find the right hardware to clamp it to the pole. I'm showing the EMT going up into the arm - but I don't think that's right. The clamp will probably move up the arm a bit to reduce the moment (force) on the clamp.

First, the clamp's job is to physically hold the lamp to the pole. EMT can't be part of that job.

I'm now thinking of cutting back the EMT (this will be a challenge) without damaging the NM (using a rotary cutter). That way, I can place a junction box closer to the roof to transition into whatever wiring I use.

Forget the NM, it's a write-off at this point. Destroy it, don't save it for use indoors. It's ruined.

No junction box. You run a continuous run of THHN, er, THWN from that indoor-outdoor transition box I mentioned earlier, straight to the lamp head proper, where you will wire-nut onto the lamp's leads. I've installed plenty of these lights, that's what you do.

As far as the EMT going off up into the lamp gooseneck without proper adapters, *I for one* don't obsess over that too badly.

However if you wanted to, you could certainly get EMT size-change couplers to "bump" to the larger pipe size. Another option is to get a **conduit body** aka gasketed pulling point, that is the size of the lamp's pipe, with appropriate fitting for it on top. Then use Rigid pipe size adapters to adapt down to 1/2" trade size on the bottom, and a common "watertight" EMT threaded fitting.

All that is commodity stuff. The folk at the electrical supply house's service desk will know exactly what you need first time (especially if you bring in the lamp w/ pipe). Just tell em "This lamp, to a straight conduit body, to 1/2" EMT" and they'll disappear for 60 seconds and come back with all the right hardware. I love electrical supply houses.

You can get the same thing done with 3 trips to Home Depot and a lot of false starts, and save $1.27. They're having a special this month, they're throwing in a free virus!

As you can see, I've thought about this way too much...

You and me both. I learned electrical by inheriting a factory building where vandals had stolen all the breakers and cut the wires at the edge of the panel (neutrals too WTH). These were non-SWD breakers worth $2, I know they weren't GFCI breakers because the place was lousy with both MWBCs and stolen neutrals. Heck of a learning experience, I had to learn the difference between art (ingenious use of MWBCs) and idiocy (furnace and fan circuits stealing neutral from anywhere, even different *services*).

 

[seharper]

By the way, there's no such thing as watertight conduit. We try to use "watertight" fittings, but seriously - it's a lost cause. I think it was here, one crew reported installing a 2" conduit on a racetrack site. They came back the next morning to fish the wire, and found 1.5 gallons of water in the pipe - from condensation alone!

Therefore all outdoor conduit is required to be treated as a wet location. That is why NM-B isn't allowed in it.

 

[sparc421]

Thank you very much for prompt and informative reply.


This is just one of many examples of the amateur work done at the facility. Sounds like it's not all that uncommon! I should mention this is a community facility, privately held by its members. The building dates back to 1967 - and they actually used stranded #12 through rigid pipe throughout. Looks more commercial than residential. The problems all arise from the various individuals that have touched it since. Some of them clearly had no idea what they were doing, or they were OK with cutting a lot of corners.



You should have seen the portion of the NM (not even NM-B, I suspect, given the age) I cut off! It was good and toasted from the heat of the 100 W mercury vapor fixture. It was "terminated" into the arm of the old fixture via an adapter from EMT to a threaded pipe elbow, largely exposed to the sun and elements.


The NM goes down a pipe and transitions to a portion not covered by conduit somewhere between the pavilion roof and building attic - I may be able to locate that if I crawl deep enough (darn, I thought my attic work was complete at this point). Then, it enters a junction box, transitions to MC, then another box, then transitions to rigid pipe from there to the panel.


I'll try to remove the NM, as that's certainly the right solution. I do have a small amount of spare #12 stranded THHN/THWN/MTW wires (red, black, white and green) in my stash (maybe about 20'). Probably enough to make this run, I hope.


The only issue I'll run into is that run between the junction box (where it transitions to MC) and the EMT (that goes through the roof). I might need to use flexible conduit here so I can run the THHN continuously, right?


I'm actually OK with the EMT simply going up into the 1-5/8" pipe "far enough" to be well out of reach if that's common practice. I'd really rather not mess with a bunch of fittings that will simply be ingress points for water and add cost; EMT up into the larger pipe may be far more "water-tight", I think. If I understand you correctly, you're OK with this approach? Once it exits the EMT, it continues up the 1-5/8" pipe into the junction box near the lamp head, at which point I wire nut it into the fixture wiring, correct?


I drew up a quick sketch of what I'm proposing. Let me know if I'm interpreting what you've suggested correctly or not.

Thanks again for your time, it's a huge help.

 

[sparc421]

I should mention that in my sketch, the "view" transitions from top view to side view right before the roof line. The rigid, boxes, EMT, etc. are all inside the attic. The run of existing 1/2" EMT is continuous from somewhere in the attic to where it ends in the photo.