Do I Need Conduit?

[fifty60]

I have 8/3 cable that is carrying 208V and 35A. For most of the equipment I work with, this would be ran inside a 1 1/4" emt until it reaches the equipment sub panel. The equipment I am seeing now does not have any EMT or any other type of conduit. It enters through a grometted hole, and then is ran freely inside of the equipment to the sub panel.

What are my requirements for using conduit in this situation? Any NFPA 70 or NFPA79 references would definitely be a great help.

 

[kingpb]

None, depending on cable type.

So, what kind of cable is it?

 

[fifty60]

They are sized from table 310.15(b)15...so I THHW/THHN..

 

[kingpb]

They are sized from table 310.15(b)15...so I THHW/THHN..

Sorry, but I'm not seeing that as a viable reference. Are you sure the Table number is correct?

Also, the conductors may have THHN insulation, but what type of cable are they in, assuming you meant multi-conductor cable when you said 8/3.

 

[mwm1752]

I would start with the uses of your particular cable be it NM, UF, MC, AC,or ?

 

[Dennis Alwon]

What is this equipment sub panel. I am not following. Is this a wireway/ trough? What kind of wiring enters this area thru the grommeted holes?

 

[fifty60]

Sorry, it is not 8/3 cable, but actually THHN/THHW wires outside of a jacket. The NEC table is actually 310.15(b)(16) (formerly 310.16) using the 2011 NEC.

The sub panel is located on the front of the equipment. The equipment is roughly the size of a standard refrigerator. The power wiring enters the back of the equipment through a grommeted opening, and then are ran loose through the inside of the equipment. The conductors are dual rated THHN/THHW that were sized using 310.15(b)(16).

 

[John120/240]

Do you have THHN/THWN conductors flying free Through this equipment ? If the equipment is UL listed then the NEC doesn't apply. I don't understand how this grommet ed hole is to work ?

 

[fifty60]

The grommet protection at the power conductor entry point is for abrasion protection only, and does not supply any strain relief. The power conductors then are ran open inside the equipment until they land in a distribution block on the equipment sub panel...

 

[fifty60]

The distribution blocks are available immediately after the conductors enter the equipment. The conductors are not "flying around" as I had originally though, they run less than a foot and land in the distribution blocks.

The conductors enter the equipment from the very top of the equipment. This entry point is approximately 7 feet from the floor, so the strain of the 7 foot of conductors to the floor is bearing down on this entry point.

Is there any way to provide strain relief with external conduit? Is there a coupling that can connect in line with the conduit at this entry point that would provide strain relief?

 

[fifty60]

This equipment does not want to run cable, it only wants the individual conductors. If it were cable, the solution would be to get a strain relief fitting. With the individual conductors, I would prefer to supply an L shaped fitting for the end user to connect their conduit to for the run to the service disconnect box.

With the sub panel located on the very top of the equipment, which is 7 feet from the ground, I do not see how the L shaped fitting would provide adequate strain relief. I am looking for a fitting of some kind that would fit onto 1 1/4 " conduit, or whatever conduit the end user decides to run to the l shaped fitting located 7 feet off of the ground....

 

[John120/240]

Your mention of an "L" fitting, are you thinking of an LB ? As far as strain relief two products come to mind, neither one does what I think you need tho.

 

[fifty60]

Right now I just have an opening on the top of the equipment. The GC who installs the equipment will be required to supply the strain relief for the power connection. If cable (SOOW for example) is selected, then it is easy enough to spec a chord grip and strain relief using NEC 400.5A

Where it gets confusing for me, is what if the customer decides to make it a permanently connected installation and not chord connected. Then, they would have the option to run individual conductors to the equipment. Here is where the tables in NEC 310.15(B)15 would come into play. The customer would likely run conduit to the opening (located 7 feet off the floor) to connect to the equipment. Since the equipment is 7 feet off of the floor, I would like to provide strain relief to minimize the force on the distribution blocks located on the sub panel.

The L shaped fitting normally would connect to a NPT threaded fitting on the equipment, and guide the wires downward. But being this high off the ground, I would still have strain on my wires and would need to provide some sort of strain relief.

So ideally, I would have a fitting that would also have an NPT threading on it so that conduit could attach. Does this exist, or would I have to provide the strain relief separate from the conduit?

 

[fifty60]

This type of strain relief is wall mountable right? And the NPT threaded fitting on the back would be used to attach a conduit to?

 

[fifty60]

I have been researching conduit in general, and have now familiarized myself with MC and Flex cables. I believe that due to the inherent vibration of the equipment, that this will be the most likely type of cable used to connect the final run of power conductors to the equipment.

If MC or Flex cable is used, is strain relief obtained from the final fitting connecting it to the equipment, or will I need to add strain relief to the conductors as they enter the sub panel? Would it be any different with flex cable?

 

[fifty60]

Can the fitting that connects the MC Cable to the equipment enclosure be considered strain relief? Does it actually provide any strain relief?

 

[kwired]

It sounds to me like your "equipment" is some kind of enclosure already housing electrical components and your source you are connecting to is within this equipment. What you are supplying is apparently butted against this original equipment - a simple chase nipple or something equivalent primarily for the purpose of "bushing" the hole is really all that is needed if I understand correctly.

 

[fifty60]

No, the equipment will be supplied without the power chord. The installer has the option of using a chord and plug, or making it permenantly connected to a disconnect. If it is permanently connected, they would likely use flex cable or MC cable.

If it is chord connected, then I know the installer can easily find a strain relief fitting so that the weight of the cable (7 feet off of the floor) is not pulling on the distribution blocks.

With the permanent connection, I am not sure how they would do the strain relief. I am not supplying an threaded NPT connection of any kind, only a knockout for a 1" hub. If the installer uses MC cable, how will I be sure that the strain relief will be accounted for in the installation? Would the fitting connecting the MC cable to the equipment supply the strain relief?

 

[kingpb]

A picture of the equipment could save a thousand words!

 

[fifty60]

If you new that you had to run 8/4 (3 current carrying plus one ground wire) AC, MC, or flex cable to a piece of equipment, white size cutout would you want to see?

No cutout is not an option. I know what the wire size is, I know the type of conduit they will likely run, but I do not know the fittings you will use to connect to the chamber. I am wanting to provide you with a cutout, but I am not sure what size to make the cutout...