Can and should 5/16" flex metal conduit be used to install undercabinet, line-voltage

[Lone Star]

Can and should 5/16" flex metal conduit be used to install undercabinet, line-voltage

direct-wired lights/luminaries?

Background
Kitchen remodel and I'm the general contractor. I do not do any electrical work myself - the reason I ask this question is that my electrician is a little lazy and tends to use whatever materials are on his truck instead of making a trip to the electrical supplier to purchase and install the most appropriate materials for the application. Before he starts his final electrical work, I want to specify how and what materials should be used to hook-up the lights. Thus, I have a few questions regarding RWA FMC, line-voltage, direct-wire Zenon lights will be installed under the cabinets. I had the electrician make 14-2 drops at every fixture location. 14-2 wires are tied back into a j-box and are on a dedicated lighting circuit. I am aware that the 14-2 Romex needs to be protected with flex conduit, but I'm unsure of which size is best. I and the homeowner prefer the look of the 5/16" vs. the 3/8" (i.e. less "chunky" looking) and the 5/16" allows a shorter bend radius (3-1/2" vs. 4" for the 3/8" FMC).


1) Southwire makes 5/16" flex metal armor, but I'm unsure if it is compliant with NEC 348.20. The NEC suggests that 3/8" is the minimum acceptable size, but if that's the case, why is 14-2 NM Romex manufactured with 5/16" metal conduit shielding?

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet226

2) If it is determined that 5/16" is code-compliant, it is even a good idea to use it? My concern is the availability of connectors that will work with this smaller diameter FMC and yet have a 1/2" male threaded end that will fit the 1/2" knock-outs on the fixtures.

3) The label on the 5/16" fmc says to not use set screw type clamps, which I assume is to prevent pinching the conduit and jeopardizing the wires. I guess "clamp-type" terminations are the best thing to use with 5/16"?

4) Can 5/16" FMC slip over sheathed 14-2 Romex or does the sheathing need to be stripped off before running the wires through the FMC?

Thanks

 

[Dennis Alwon]

First off I don't think it is appropriate for us or you to micro manage the job of the ec. If you have an issue with him then talk to him or get rid of him.

That being said nm cable in many areas is allowed to come out for uc lights unprotected. If not in that area then as long as the nm fits it generally is not an issue but again I don't think this is your position to micromanage how a sub does his job unless it is not compliant. Hopefully the inspector will deal with that

 

[iwire]

Electricians cannot install that 5/16" flex, that is only for use inside other listed equipment. Look at the link you provided and notice the asterisk beside 5/16" on the table.

 

[ceb58]

direct-wired lights/luminaries?

Background
Kitchen remodel and I'm the general contractor. I do not do any electrical work myself - the reason I ask this question is that my electrician is a little lazy and tends to use whatever materials are on his truck instead of making a trip to the electrical supplier to purchase and install the most appropriate materials for the application. He may not be lazy, it may be the GC low balls him and he has to watch his trips and material. Before he starts his final electrical work, I want to specify how and what materials should be used to hook-up the lights. That's fine, don't cry when there is an extra charge. Thus, I have a few questions regarding RWA FMC, line-voltage, direct-wire Zenon lights will be installed under the cabinets. I had the electrician make 14-2 drops at every fixture location. 14-2 wires are tied back into a j-box and are on a dedicated lighting circuit. I am aware that the 14-2 Romex needs to be protected with flex conduit, but I'm unsure of which size is best. I and the homeowner prefer the look of the 5/16" vs. the 3/8" (i.e. less "chunky" looking) and the 5/16" allows a shorter bend radius (3-1/2" vs. 4" for the 3/8" FMC).


1) Southwire makes 5/16" flex metal armor, but I'm unsure if it is compliant with NEC 348.20. The NEC suggests that 3/8" is the minimum acceptable size, but if that's the case, why is 14-2 NM Romex manufactured with 5/16" metal conduit shielding? Its not.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet226

2) If it is determined that 5/16" is code-compliant, it is even a good idea to use it? My concern is the availability of connectors that will work with this smaller diameter FMC and yet have a 1/2" male threaded end that will fit the 1/2" knock-outs on the fixtures. Its not

3) The label on the 5/16" fmc says to not use set screw type clamps, which I assume is to prevent pinching the conduit and jeopardizing the wires. I guess "clamp-type" terminations are the best thing to use with 5/16"? You are correct too bad you cant use it.

4) Can 5/16" FMC slip over sheathed 14-2 Romex or does the sheathing need to be stripped off before running the wires through the FMC? No

Thanks

Just get the EC with the home owner so they can work out a solution for the install and walk away slowly. If there is an extra charge just pass it on to the customer for giving them what they want.

 

[petersonra]

I am not sure there is any requirement to use metal conduit of any kind for this type of install. If that is the case, and I am not 100% sure it is, then if someone chooses to route the cable that is not required to be in conduit at all inside of anything, it just does not matter much how it is installed as long as the cable is not damaged.

Presumably it could be installed inside anything and be code compliant. Like a hollow curtain rod.

Personally, I think plug mold would work pretty well and look nice as well..

 

[John120/240]

How far from the wall are these under cabinet fixtures to be mounted ? I have always kept the ones I installed a 6" levels thickness from the sheetrock or tile. Not enough exposure to worry about. When using plugmold a 6" levels thickness then under cabinet fixture . Never a problem.

 

[electrofelon]

That being said nm cable in many areas is allowed to come out for uc lights unprotected.

Agreed. There seems to be this very common belief that NM cant be exposed, but this is not true at all (in dwellings). As long as it closely follows the surface and is not subject to physical damage, it is fine. That said, I have come across state and local codes that are more stringent on this issue.