Electrical caulk for MC PVC cable connectors

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OldSalt

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Project Description: I'm a homeowner installing outdoor light fixtures on my 7' deep balcony, across the front of my home. I'm trying to do this properly to code. However, I have a problem, and intend to resolve it by the "whatever works" method.

The fixtures will be mounted on the support posts, in front of and underneath the balcony, overlooking the garage and driveway below. The balcony is covered, but not water proof. We occasionally get some snow on the deck, and some rain mist may hit the Trex deck, but unless we're washing the deck with a hose, not much water. However, it is technically classified as a wet area.

Therefore, I'm running Southwire MC PVC 1/2" 14/4 cable (actually, 14/3 plus one coated wire for ground) underneath the balcony, and surface mounted on the 12" x 12" front posts. I've mounted 2-gang weather proof junction boxes at either end of the balcony, and will route the cable from those boxes down the post, and into round weatherproof boxes.

The posts are clad with 3/4" cedar veneer, and I've made 3/4" cedar mounting blocks for the fixtures. That's 1.5" of veneer total, which will handle the offset produced by the (1.25" deep) round weatherproof boxes (i.e. round holes will be cut into the post veneer and blocks, providing sufficient depth so that the cedar is flush to the round boxes. The (1/2" deep) light fixtures will be mounted over the (1.25" deep) round boxes, and standard colored silicon caulk will be used to seal around the base of the lamp fixtures. Also, while the MC cable will be fed from above down the posts, I'm entering the round box on the posts from a side port (i.e. rather than from the top), to reduce the possibility of water eventually entering the MC conduit or connectors. The 2-gang junction boxes will have weatherproof covers installed. The round light fixture boxes will depend on the light fixture and silicone seal for weatherproofing, as there will be no weathertight cover mounted underneath the light fixture, over the round box.

I'm using what I believe are the proper type of connectors for the MC PVC 14/4 cable, and the weather proof boxes, i.e. Bridgeport 596-DC2 1/2" PVC Jacketed MC/TECK Cable Connectors.

I haven't mentioned quite a few things, i.e. the circuit is switched, 15AMP (i.e. I ordered installation of all homes lighting circuits as 15A, and plug receptacles circuits as 20A, when I built the house). Power routes from the interior garage wall via MC PVC cable from a metal box in the outside wall, out to the first junction box. Connections will be properly grounded to screws inside the metal boxes.

Problem Description: When I install the 1/2" MC PVC cable into the connectors, and screw them tight, they are neither air tight nor water tight. It almost seems as though the Bridgeport connectors are too large for the cable. (I could find no 3/8" connectors in the Bridgeport catalog, and finding ANY connectors for MC PVC cable was difficult, period.) Since these connectors retail from about $15 to $27 each, and I picked these up for $6 each, after a long search, I'm not ready to start over, looking for a better fit. (Example: I originally ordered what I thought were 15 connectors for about $30 at a local electrical supply, only to find after two weeks of waiting that (a) they were still unavailable, and (b) they were $30 A PIECE, a box of #15 minimum order!)

Proposed Solution: Install the Bridgeport connectors I have on hand into the boxes, install the cable into the connectors, screw the connector seals closed, and apply an elastomeric (i.e. rubberized) caulk in the back of the connectors, to fill them and ensure no water penetration through those connectors into the boxes.

Yes, I know that THIS solution isn't code. Those Bridgeport connectors are support to seal air and water tight. I'm comfortable with this solution on MY house, because I used all the proper components and methods otherwise, and that water will not penetrate those boxes through those connectors when I'm finished.

Question: Is there an actual product made for sealing weather proof connectors or electrical boxes against the exterior elements? I've seen some silicone products on Amazon, but I don't see how they're better than the product I intend to use (i.e. a elastomeric caulk I use for sealing concrete cold joints, also used for gaps on bridges, and cold joints on tennis courts, and etc.).

Thanks!


Note: I had forgotten that I had written about and discussed this project last month. (Early senility!) For reference (with a couple of pix), here's a link to that thread.
https://terrylove.com/forums/index....h-lights-exterior-mc-cable.96662/#post-695383
 

wwhitney

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I'm using what I believe are the proper type of connectors for the MC PVC 14/4 cable, and the weather proof boxes, i.e. Bridgeport 596-DC2 1/2" PVC Jacketed MC/TECK Cable Connectors.
. . .
(I could find no 3/8" connectors in the Bridgeport catalog, and finding ANY connectors for MC PVC cable was difficult, period.)
The 3/8" version is just Bridgeport 595-DC2. That has a spec on the allowable OD of the PVC Jacketed MC of 0.50" to 0.61". The 1/2" version 596-DC2 is spec'ed at 0.61" to 0.69". The Southwire 14/3 has an OD of 0.581". [Only flexible cords count the EGC in their nomenclature, as it is optional (e.g. appliances with 2 prong plugs), while in building wire it is never optional.]

So you simply have a mismatch between your cable size and your connector size. I suggest either getting the correct connectors, or getting new cable that has the larger OD you require. E.g. if you only need 2 (circuit) conductors, Southwire's 10/2 Jacketed MC has an OD of 0.665". Or if you actually require 3 circuit conductors, you'd have to go up to 10/3 Jacketed MC (0.679" OD), as the 12/3 Jacketed MC has an OD of 0.604".

On the correct connectors, these guys show them in stock for $16 each, plus shipping (no affiliation):

https://www.gordonelectricsupply.com/p/Bridgeport-595-Dc2-595-Dc2-Pvcjkt-Connector/5773788

Cheers, Wayne
 

OldSalt

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The 3/8" version is just Bridgeport 595-DC2. That has a spec on the allowable OD of the PVC Jacketed MC of 0.50" to 0.61". The 1/2" version 596-DC2 is spec'ed at 0.61" to 0.69". The Southwire 14/3 has an OD of 0.581". [Only flexible cords count the EGC in their nomenclature, as it is optional (e.g. appliances with 2 prong plugs), while in building wire it is never optional.]

So you simply have a mismatch between your cable size and your connector size. I suggest either getting the correct connectors, or getting new cable that has the larger OD you require. E.g. if you only need 2 (circuit) conductors, Southwire's 10/2 Jacketed MC has an OD of 0.665". Or if you actually require 3 circuit conductors, you'd have to go up to 10/3 Jacketed MC (0.679" OD), as the 12/3 Jacketed MC has an OD of 0.604".

On the correct connectors, these guys show them in stock for $16 each, plus shipping (no affiliation):

https://www.gordonelectricsupply.com/p/Bridgeport-595-Dc2-595-Dc2-Pvcjkt-Connector/5773788

Cheers, Wayne
That explains my problem. Thanks.
 

OldSalt

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Or a couple of wraps of vinyl electrical tape around the cable where it sits in the connector. Not code But.......
Yeah, I thought of that, but since it's exterior, I want something a little more liquid based to seal it. Tape, even if it's compressed in the fitting, eventually gives way. Silicon caulk is warrantied for 40 years. I decided not to use the elastomeric stuff, because it's fairly permanent. If the fitting had to be opened up, I'd have to cut everything out of the fitting, probably replace the fitting and maybe even the cable. I'll probably use the KISS method (i.e. "keep it simple ..."), and just go with a caulk, possibly some stuff that's high temp/fire rated that I've used around the fireplace. At least, it's removable for future service. I mean, if I'm gonna jury rig it, might as well go big, right?

I saw a product on Amazon that is silicon for electrical work, probably used for things like circuit boards. I was just trying to determine if there's anything electrician use to seal wires or conduits, in addition to the mechanical devices, that's to code. I understand that you don't want combustibles inside the box, but this won't be inside the box, and should be no more combustible than the PVC coatings on the wires.

Thanks.
 
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