Liquid tight FMC vs PVC

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Old 03-28-18, 11:08 AM
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Liquid tight FMC vs PVC

I have about 100 feet of outdoors conduit I have to run for my floodlight/camera system. I am going to have a junction box in the middle (so think of 2 individual 50 feet runs on the left and right of that box, 2 lights in each run). This is a 20A circuit and I will run 2x12 gauge THWN conductors and separate ground.

i just realized that there are two kinds of this flexible liquid tight conduit. One has a metal conduit built in vs another that is just fully PVC. Which one of these should I use?

The conduit will run along side of the gutters topside of the wall if that makes a difference. Nothing will touch the ground.

I have a 12 gauge NMB exiting the house via this outdoor junction box.

lastly, I have plans to also run low voltage landscape lighthing on this circuit so what I want to do is to have a GFCI outlet that is the load to that junction box
 
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Old 03-28-18, 12:10 PM
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Hi, FMC can not be used outside and also has limitations on the length,PVC is your best bet .
Geo
 
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Old 03-28-18, 12:28 PM
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Originally Posted by Geochurchi View Post
Hi, FMC can not be used outside and also has limitations on the length,PVC is your best bet .
Geo
This is not FMC. This is what's called Liquid Tight FMC which is basically a PVC wrapped FMC inside.

So the question is:

1) https://www.homedepot.com/p/AFC-Cabl...4-00/204794288

VS

2) https://www.homedepot.com/p/AFC-Cabl...0-00/204794278

The cost difference between the two isnt concern. The FMC one says ground bonding is required. Does that mean if I used that, I dont need to run a ground wire and I simply connect the conduit to my metal outdoor junction box via metal connector and then the line NMB from inside the house has its bare ground wire connected to the junction box via ground screw? but then what happens if somewhere there is a breakage on this metal conduit (exterior damage etc). I'm just not sure if it's a lot of headache to deal with this. Because all I m running is a hot and a neutral, 2 conductors, running ground isn't a lot of work for me.
 
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Old 03-28-18, 12:28 PM
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FMC is what's commonly known as Seal-Tite. It can be used outdoors as it is rated as water and sunlight resistant. It can be buried if direct burial is stamped on it. However.... due to it's flexibility it makes a poor choice for long exposed runs as it is hard to keep straight and neat looking. There is no limit on the length used as long as it is properly supported.
 
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Old 03-28-18, 12:36 PM
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Originally Posted by PJmax View Post
FMC is what's commonly known as Seal-Tite. It can be used outdoors as it is rated as water and sunlight resistant. It can be buried if direct burial is stamped on it. However.... due to it's flexibility it makes a poor choice for long exposed runs as it is hard to keep straight and neat looking. There is no limit on the length used as long as it is properly supported.
But should I use that FMC or just the regular PVC liquid tight? It seems to me the regular PVC flexible liquid tight without FMC is easier to deal with? If I use the FMC, won't I have to also use metal connections which means rust/cross threading/etc?

When I look at the cross section of each of these conduits, the FMC has a much thinner outer PVC jacket vs the pure PVC one but all in all both have equal amount of outer thickness (in total).

to make it straight, I will use more of those U hanger things, not much more I can do. I don't think if Iused SCH 40/80 it would make a difference because that stuff also sags with heat changes and there is no way I can use the actual galvanized metal FMC, its above my pay grade.
 
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Old 03-28-18, 01:27 PM
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My choice would be the Non-Metallic Liquidtight.
 
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Old 03-28-18, 01:30 PM
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I would use Ridged for those long runs. It will stay straight and look good years from now.
 
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Old 03-28-18, 05:08 PM
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Unfortunately the rigid steel pipe is too much work for me and above my pay grade. I neither have the truck to transport them nor tools to thread/cut or the knowledge to bond the metal and deal with various PVC to rigid transition points.

if i use those hanger things say every 2 feet, i dont see how much this can sag? I am also going to paint everything white to match the color.
 
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Old 03-28-18, 05:33 PM
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Also, I read conflicting info on length restriction for LFNC (liquidtight flexible non metallic conduit). Is there a 6’ length restriction or not? A few places say that as long as it is secured every 3’ and 12” within any box, its okay?
 
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Old 03-28-18, 06:04 PM
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I believe the question is why not use rigid PVC, not metal.
 
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Old 03-28-18, 06:18 PM
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Good question I dont know. My knowledge on this is limited by the inventory my local home depot carries and rigid pvc isnt something they have

how does this work? My constraint is I have difficult bends and I have to use this liquid tight flexible non metallic tbere. Can I transition from that to rigid?
 
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Old 03-28-18, 06:39 PM
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I only like to use liquid tight flexible metal conduit over non-metallic . The metallic is much easier to install wire into.

rigid pvc isnt something they have

Yes, they do. It is the gray PVC that is next to the metallic conduit. They carry both Sch 40 and Sch 80. You can buy all the fittings you need including pre-bent 90's, 45's, and sometimes box offsets. If you really want to have some fun you cam make your own bends using a torch, heat gun, BBQ grill, etc
 
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Old 03-29-18, 03:46 AM
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I see. Can I mix and match the liquid tight with rigid? How?

no homedepot sells schedule 80 within 100 miles radius of me. Maybe in this area for some reason it is not used?

Also regarding liquid tight, the one that has metal in says bonding ground required. What does that mean?

i m a bit lost because about a month ago in another thread everyone was telling me not to use the regular pvcas it has issues sagging and also requires expansion joints and in general doesnt last long. I was then advised to use this liquid tight stuff.

i have a lot of bends and strange obstacles like crossing over both radon pipe and electrical main from street or doing back to back bends on corner walls under gutter pipes. Using those premade 45/90 pvc turns etc just doesnt work there. I would have to use heat gun and bend things myself. Its not easy.

LFNC on the other hand would be very easy. But i dont know how to use the metal one. Does it require me to use metal connectors or can i use plastic threaded ones?

https://www.homedepot.com/p/RACO-Liq...02-8/100134172

vs

https://www.homedepot.com/p/1-2-in-L...T5-1/202284584

vs

https://www.homedepot.com/p/1-in-Non...10-1/202284604
 
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Old 03-29-18, 04:17 AM
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"Also regarding liquid tight, the one that has metal in says bonding ground required. What does that mean?"

It means you have to include a green-insulated equipment grounding conductor along with the power conductors. The spiral metal under the jacket is not sufficient to act as a grounding conductor.

Liquid tight flexible metal conduit uses special connectors. I have never seen them in anything but zinc-plated metal but maybe there are plastic fittings of which I am unaware.
 
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Old 03-29-18, 05:11 AM
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If thats the case, i.e you still need a 3rd wire for EGC, then why would anyone want to use the metal one? Its much harder to cut/bend, more expensive, connectors probably not as easier to insert (i m sure pure plastic one can be heated at the tips with heat gun to make the connectors easier to insert).

i thought the entire point of the one with metal jacket inside was that it didnt require additional EGC.

edit: just found this link. So i guess its the 6’ requirement thats the issue? But i thought that rule changed with NEC2014

https://jadelearning.com/jadecc/cour...p?imDif=3055.0
 
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Old 03-29-18, 05:12 AM
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Article 348 in the NEC explains uses for FMC ,not to exceed 6’ also LFNC B is not the same thing, I would consider using LFNC B. in long lengths as pulling in conductors could be a problem, ground conductor may not be required but I always pull one in .
 
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Old 03-29-18, 05:30 AM
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You can mix Liquidtight and rigid PVC conduit. You don't need Sch80 PVC unless the conduit is installed in a place it's subject to damage. Sch40 is fine in most cases. Remember not to exceed 360deg of turns between pull points, so don't go wild with the bends using the flex between boxes.
 

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Old 03-29-18, 06:16 AM
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I thought rigid one was sch80. I m very confused here. When I search homedepot.com for rigid pvc, all i m getting is 2 connectors and nothing else. Can you show me where these rigid pvcs are? Also I thought LFNC to any glue based conduit was not allowed due to how the glue works and connections are not properly made. Do they make an adapter?
 
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Old 03-29-18, 06:27 AM
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Search "conduit". . .
 
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Old 03-29-18, 06:30 AM
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More common is schedule 40 PVC conduit and is fine for your purpose.

Example: https://www.homedepot.com/p/3-4-in-x...7454/100129197
 
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Old 03-29-18, 06:37 AM
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Ok so you are talking about regular sch 40 gray conduit

Its funny because thats what I was going to use initially but was advised here not to use it as it tends to sag and is difficult to bend/glue is a mess and was told to use the liquidtight pvc (which up to the point I didnt even know).

alright so back to just pvc, now I have to figure out how to bend that stuff because even with a 1600W heatgun I have, after minutes it wont even bulge. Should I use a propane torch? Honestly the only bend where I need a custom bend is 1 place. Everywhere else I can use regular 30/45/90 degree premade bends
 
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Old 03-29-18, 08:31 AM
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For complex bends use a foot or two of Sealtite (FMC). Connect with a cement to thread adapter coupling.

but was advised here not to use it as it tends to sag and is difficult to bend/glue is a mess
Space the clamps closer together than required, maybe every two feet and use the two hole ones.. Insert mason's twine as you assemble and glue it. Never thought it was that messy.
 
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Old 03-29-18, 08:48 AM
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Sorry can you help me understand what you mean by sealtite fmc?

Do you mean liquid tight flexible metallic conduit, exterior pvc and interior metal that is flexible?


So what you are saying is on PVC side, use a female threaded adapter. The pvc side glued in and the female side is then connected to liquidtight male adapter?
 
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Old 03-29-18, 08:55 AM
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Do you mean liquid tight flexible metallic conduit, exterior pvc and interior metal that is flexible?

YES.

what you are saying is on PVC side, use a female threaded adapter. The pvc side glued in and the female side is then connected to liquidtight male adapter?
Yes.

Out of the junction box use an offset nipple to get it flat to the wall then two hole clamps.
 
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Old 03-29-18, 09:44 AM
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Thank you.

one last question, is there anyway to mount the pvc conduit pipe flush on the corner? I.e mount the bracket so that one screw goes into the wall and another goes up top into the runners under the gutter?

so in essence, instead of having both screws at 180 degrees, mount them at 270 degrees.

I want to do this just purely for cosmetic reasons. I dont know if its a good idea, or if its allowed.
 
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Old 03-29-18, 09:56 AM
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into the runners under the gutter?
What is a "runner under gutter"?
 
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Old 03-29-18, 10:48 AM
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Sorry I meant to say soffit cover they have which runs under the gutters. So instead of both screws on soffit, one goes to soffit and another goes to the 2x12 board that sits perpendicular on the actual wall

actually let me first ask, is it okay to run this along the soffit cover? Can the soffit cover carry this weight? I think unless I hit the rafters which i wont be easily, the conduit clamps will be just secured to soffit. Is there a better way to do this?
 
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Old 03-29-18, 11:11 AM
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Have you considered running cable inside the soffit? I have done this by removing soffit vents or cutting holes and then covering them with new soffit vents.
 
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Old 03-29-18, 11:16 AM
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I have not. I m not sure what I will find inside them and I dont know if I can put it back together. I dont know how to take it apart. I m guessing if I could though, I would have to transition from THWN to NMB indoors through the rafters and then back to THWN? Wouldnt that require more work as far as putting junction boxes?
 
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Old 03-29-18, 11:51 AM
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The soffits on my roof are quite small meaning probably there is no space between the soffit and the rafter. They probably made the soffits just long enough to cover the rafters so the only way to fish the wire inside a soffit is if I bore a hole in every single rafter which considering I have to run this wire on 60% of the side of my house, its a lot of holes to bore.

Assuming I have to hang the conduit exterior of the soffit, would the soffit cover carry the weight of the pvc conduit? Is it okay to mount the conduit on the soffit?
 
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Old 03-29-18, 12:31 PM
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Yes and yes. ........................................................................................
 
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Old 03-29-18, 12:42 PM
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Thanks I appreciate for your help. I will just mount directly on soffit
 
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Old 03-29-18, 02:53 PM
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Assumes soffit is plywood.
 
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Old 03-29-18, 02:57 PM
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I hope you don’t have a accessable attic! Just thought I would ask.
Geo
 
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Old 03-29-18, 04:12 PM
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Originally Posted by Geochurchi View Post
I hope you don’t have a accessable attic! Just thought I would ask.
Geo
Of the 4 lights/cameras I need to install, 3 of them are on the part of the roof without any access from attic. Its a split level house and basically this is the area above the living room/below 3rd level bedroom and there is no way to get in there. Only 1 light could technically be done from attic, but that would mean it would be on a completely different circuit and I dont want that. I already did all the interior prep work for this circuit, installed its own junction box, ran a cable upstairs inside walls and put a switch to control it. I understand its not ideal, but i m hoping after I paint everything white, it wont look terrible.
 
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Old 04-02-18, 05:17 AM
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Just an update, I completed the project with the help of my wife (who patiently stood by my side) in exactly 2 days (thats 7am-7pm first day, 730am to 5pm second day with the exception of 30-40 min lunch break). It was a lot of work and if I hired an electrician there is no way they would have gone the extra mile in a lot of the areas like I did (which is fair, no one is going to care about your property like you do) not to mention they would charge me probably 5-6k plus material. I actually did a pretty good job and every single step went without a hiccup as I had been planning this for weeks. So the amount of time I spent wouldnt have been cut short with an electrician.

all in all I laid 120 ft of conduit, 4 light fixture boxes, 1 big junction box, plus 3 other smaller junction boxes. Lots of turns and specially engineered connections while making sure I never reached the 360 degree rule and followed the 12” from the box and every 2’ elsewhere for clamps. Everything works, I honestly didnt think I could pull it off without an issue.

I wanted to come here and THANK you guys for all your advice. Here are some of the things I learned (some were already said by others here)

- Those flexible liquid tight conduits are IMPOSSIBLE to fish wires in, even for say 1 foot if they are in an awkward position. There is no way you can use that stuff and pull wires say 30,40, or 50’ runs with bunch of curves and bends. Their inside isnt smooth like rigid pvc since their adapters are “screwed” in. This makes fishing part so difficult.

- You absolutely must put everything together first then fish wires. I didnt try otherwise but while going through the conduit phase I realized it would be impossible to do it in pieces. The glue would probably get all over the wires and damage the insulation. Its not a glue, but solvent and as such will dissolve plastic.

- Running smaller 14 awg wire might have been easier but in some situations I dont think the thing wire would survive the abuse as much as 12 awg did.

- 1/2” conduit should not be used for anything but very small projects. Dont let the conduit fill factor mislead you. Even with a 3/4” conduit, it was difficult to fish 3 x 12 awg conductors.

- Even though these are security cameras/flood lights, I am glad I took the extra step and added a switch upstairs as it makes troubleshooting much easier. You have to have a switch somewhere where youv have to observe from the location of the switch.
 

Last edited by Derstig; 04-02-18 at 05:46 AM.
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Old 04-02-18, 05:44 AM
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Thanks for letting us know the outcome.
 
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