Adding porch lights: Exterior MC cable?

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OldSalt

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I'm extending a NM porch light cable in my garage wall, out to two posts supporting the overhead, 7' semi-covered deck, which is in front of the garage. On the posts, I intended to put three lamps, one on one side, and two on the other. The installation will be a surface mount. My original choice was MC armored cable, 14/2. I know just enough about electrical work to be dangerous, but I try to keep in code compliance.

My intended supply list included:
- A 1-gang interior rated metal box for the junction between the ROMEX in the wall, and the MC cable exiting the wall, though the sheathing and siding, and tracking close to the joists out the the front of the deck.
- Three, 1-gang exterior/waterproof metal boxes:
** 1 box for the junction between the #1 MC cable - supply from the garage wall, #2 MC cable routing down the 1st post to the lamp, and #3 wire routing horizontally across/underneath the joists over the the second & third post lamps.
** 1 box junction under the deck, between the first junction and the second/third post lamps, for future lighting underneath the deck. (The MC cable would pass through.)
** 1 box at the second post, to split power between the two lamps on either side of the post.
- Three weatherproof covers for the junction boxes.
- Three shallow depth, round, 1/2" electrical box to mount on the posts. (The posts are structural lumber, veneered with 3/4" cedar. The plan was to cut out a circle through the veneer in which to embed the box, so that the lamp can mount flush over the post, hiding the box, and route the MC cable/power to the box.)
- Plastic anti-short bushings for the MC connections.
- Standard connectors for the MC cable to the four junction boxes. *** more on this! ***
- 1/2" Drive Strap Nails to connect the MC cable to the balcony deck's joists.

I found out that I was in trouble when I couldn't figure out how to connect the MC cable to the junction boxes and ensure a watertight fit. I was planning on using these:
https://www.lowes.com/pd/Sigma-Elec...Conduit-Compatible-Conduit-Fitting/1000152539

I looked at everything in their inventory, and I couldn't find anything available for connecting MC cable to a exterior, weatherproof junction box. Then I questioned my assumptions. Is MC cable actually rated for exterior use? Maybe that's why there are no fittings to connect MC cable to an exterior junction box.

After a bunch of research, it seems to come down to what code defines as a wet area, and certainly my installation would require cable rated for a wet area, and MC cable is not that animal. I don't want to run EMT or PVC conduit of any kind, particularly down the posts to the lamps (too obvious). I thought that painted BX/MC would blend into the background and be less noticeable (not to mention, easier to install). I looked up Southwire's offerings, the maker of the Armorlite MC cable I had purchased. They do market an MC PVC cable that's rated for wet areas, including underground burial. However, I can't find that product for sale, even at Platt Electric (per their online inventory), or at a second electrical supply.

Moreover, the same question would apply. What kind of connectors would I use to connect the MC PVC cable to the weatherproof junction boxes? Is it code compliant to run an armored cable in a mostly dry, wet area? Do exterior options exist that don't involve installing NM through conduit?

This is a pretty simple project, but if I don't get the materials right, nothing will be right (including code compliance). I'm sure 80% of homeowners would just run the MC, figuring that it's a covered deck, mostly dry. Plus, they can't find anything else at the big box stores, which is where most of us find our supplies.

Can someone throw me a life line, here? Thanks.
 

wwhitney

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How about a picture of the conditions? Whether and how well the deck is covered will determine if your wiring is in a dry, damp, or wet location.

For a wet location cable, your basic options are UF and jacketed MC. The latter is available, e.g. at Platt (since you mentioned that vendor):

https://www.platt.com/platt-electri...ltiple/122MCSPVCX250/product.aspx?zpid=697427

The jacketed MC cable requires special connectors, such as these:

http://www.aifittings.com/landing/ltmc50/

Note that the above connector is designed to connect to a knockout; not sure if it's appropriate to use in a threaded entry, but if you do, it would probably be appropriate to use a thread sealant.

I don't think a 1/2" pancake box is suitable to use outside, not sure. Also, the interior of outdoor conduit is considered a wet location, so you can't run NM cable inside of it. You would need to run individual wet location rated conductors, such as THWN.

Cheers, Wayne
 

OldSalt

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Hi Wayne,

I think you just about nailed it. The item you mentioned is $2.12 /ft, and I'm going to try to use this (if available) for $1.27 /ft. It's rated for sun, wet, and burial.
https://www.platt.com/platt-electri...GSTRX1000/product.aspx?zpid=769915&reload=yes

The APC Connectors are pricy, but these are what the brochure recommends:
https://www.platt.com/platt-electri...arrel/AFC/0125-15-00/product.aspx?zpid=653059

(This is their cut sheet.)
https://rexel-cdn.com/Products/Multiple/122MCSTLGSTRX1000.pdf?i=90E78FA7-ED2A-4171-9B33-88BD8EE2EFBA

As far as the pancake box for the three lights, I believe the electricians mounted the original porch lights against the house with a simple ceiling pan.
https://www.lowes.com/pd/RACO-1-Gan...w-Ceiling-Pans-Ceiling-Electrical-Box/1099827

When I asked about it, they said that the light fixture itself was rated as a weatherproof box, and the pan was simply to mount the lamps. This area is exposed, so I believe that the round box with the light fixture covering the top, is sufficient. (I'll be caulking the fixture to the post as well with an elastomeric, a.k.a. rubberized product, as a gasket.)
https://www.lowes.com/pd/Sigma-Elec...tandard-Round-Exterior-Electrical-Box/3136835

I've included several pictures of the wall (i.e. where the MC cable will exit to provide power, under the balcony with the first post, and both the longer run under the balcony to the second post. There is only Trex above (i.e. the balcony is not dried in), but there's a second balcony above the 1st, with a full, weatherproof roof covering it. So, in reality very little rain, snow, or moisture reaches below, even when hosing the deck above, but it's not fully dried in, thus it's by code definition a "wet area".

So, I'm off to return a bunch of unusable junk to the big box store, and to Platt to get the MC PVC cable and fittings (though they may have to be ordered and shipped; still checking).

Thanks a bunch!
 

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wwhitney

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As far as the pancake box for the three lights, I believe the electricians mounted the original porch lights against the house with a simple ceiling pan.
My concern about the pancake box is whether it's going to end up as well protected from the weather as a box cut into the siding of the house will be. If it's not as well protected, you could argue it's in a wet location, and you need a wet location rated box.

And how to do you terminate that jacketed MC cable to a pancake box? The use of a pancake box suggests limited depth between the face of the post and the face of the cedar wrap. While that jacketed MC connector is long and the only ko in the pancake box is in the back of the pancake box.

So I think you may be better off using a 1-1/2" deep round outdoor box like you linked to. If the depth available is less than 1-1/2", then you could use a 2x cedar mounting block behind the light fixture to hide the box and jacketed MC cable connector.

Cheers, Wayne
 

OldSalt

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My concern about the pancake box is whether it's going to end up as well protected from the weather as a box cut into the siding of the house will be. If it's not as well protected, you could argue it's in a wet location, and you need a wet location rated box.

And how to do you terminate that jacketed MC cable to a pancake box? The use of a pancake box suggests limited depth between the face of the post and the face of the cedar wrap. While that jacketed MC connector is long and the only ko in the pancake box is in the back of the pancake box.

So I think you may be better off using a 1-1/2" deep round outdoor box like you linked to. If the depth available is less than 1-1/2", then you could use a 2x cedar mounting block behind the light fixture to hide the box and jacketed MC cable connector.

Cheers, Wayne
That's a good idea, i.e. adding a cedar block to the post. I was intending on using this, which is weatherproof (just to make sure we're on the same page). https://www.lowes.com/pd/Sigma-Elec...tandard-Round-Exterior-Electrical-Box/3136835

However, placing the lamp fixture over the box isn't going to ensure a weathertight seal. I'll look into this further. If I add a plate with a 1/2" threaded hole to the above fixture to seal it properly, then the fixture wires can feed into the box properly via a sealed fitting but, those things protrude out a couple of inches).

(I was always wondering what I was going to do with the cedar scraps that were too expensive to just throw away. Lol. That'll work. )

Edit: Just found out that the cable I linked to above is a non-stocked, special order, 1000' minimum item, so I guess I'll be shopping more.
 
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wwhitney

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However, placing the lamp fixture over the box isn't going to ensure a weathertight seal.
What's the fixture? Usually the instructions tell you to silicone the fixture's mounting plate to the mounting block on 3 sides (not the bottom). Or it cold have a 4" round opening in the back, which can compress the gasket on a 4" round box as long as the box is not recessed (not sure if that strategy is actually used).

Just found out that the cable I linked to above is a non-stocked, special order, 1000' minimum item, so I guess I'll be shopping more.
I think there are at least a couple retailers on the web that will sell it to you by the foot and ship it.

Or you could use UF and fashion a cedar U-channel out of a 1x2 or 1x3 or 2x3 to cover it.

Cheers, Wayne
 

OldSalt

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What's the fixture? Usually the instructions tell you to silicone the fixture's mounting plate to the mounting block on 3 sides (not the bottom). Or it cold have a 4" round opening in the back, which can compress the gasket on a 4" round box as long as the box is not recessed (not sure if that strategy is actually used).


I think there are at least a couple retailers on the web that will sell it to you by the foot and ship it.

Or you could use UF and fashion a cedar U-channel out of a 1x2 or 1x3 or 2x3 to cover it.

Cheers, Wayne
Yeah, I've been looking all over the web. In the few places that actually carry it (or will special order it), it's a 250' minimum (spool). I have a RFQ into one place for 60' - we'll see how they respond.

I can't believe that apparently no one ever uses this stuff on exterior applications. I'll let ya know if I come up with a solution.
 

OldSalt

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Well, I found 50' of MC PVC 14/4 stranded that's actually designed for use in an HVAC split-system connection.
https://www.homedepot.com/p/Southwi...803/205404476?source=shoppingads&locale=en-US

Price was right, quantity will probably work, and I hope it's still an half-inch pipe (appears to be so). I also found some 1/2 connections, MV PVC rated, #15 for about $28 from Platt. I can't BELIEVE how difficult it's been to get these components. I've looked all over the web, and have found the same type of connectors for $20 a piece, and I've told you the story on sourcing the cable. The cable won't arrive until the end of the month (oh boy, I love installing in freezing Northern Idaho weather, Yippee!!!).

I'll update on how it works out. Wayne, you helped a bunch, and I appreciate it.
 
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