Large Wire in Control Cabinet

Tim Ganz

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T
Join Date
Dec 2010
Location
Dallas, Texas
Posts
689
I need some # 2 wire for a section in my control cabinet and don't want to use THHN as it is difficult to work with inside a panel.

I have seen some wire call RHW used for large installs before and it has more of a rubber insulation and is very flexible.

I don't know if they make MTW that size?
 
Last edited:
No MTW that size. The problem with the extra flex cable, often called DLO (Deisel LOcomotive) cable is that the fine stranding cannot be used in mechanical lugs. The only approved termination method is to use special high pressure crimp lugs listed for that exact purpose, then use studs or bolts to terminate on the device, which of course implies that the device can accept that type of termination. If that works for you, by all means, use it. You just need to make sure the DLO has the dual rating as RHHW, not all brands do. Only the RHHW versions are UL listed.
 
jraef said:
No MTW that size. The problem with the extra flex cable, often called DLO (Deisel LOcomotive) cable is that the fine stranding cannot be used in mechanical lugs. The only approved termination method is to use special high pressure crimp lugs listed for that exact purpose, then use studs or bolts to terminate on the device, which of course implies that the device can accept that type of termination. If that works for you, by all means, use it. You just need to make sure the DLO has the dual rating as RHHW, not all brands do. Only the RHHW versions are UL listed.
Click to expand...

I did not know the fine stranded stuff could not be used in mechanical lugs. We have a lot of panels that come from the OEM that way though. Is this in the NEC code book somewhere? I would like to have it for future reference.

THis wire is needed for 1 starter in 1 cabinet and to go from the disconnect terminals to the power distribution block which is 100 amp disconnect feeding the distribution block.

What is another choice more flexible than THHN?
 
Tim,

use caution when it comes to cable types.
i had a contractor pass off some of this cable as being acceptable for a job when it was in fact it was not even listed for the application. we rejected his wiring because it wasn't rated for the job. he said it would work because he used it on another job and it was accepted. he ended up buying a cable 4 times more expensive that had the ul rating on the cable for the intended purpose.


you must use the nec code book to verify the type of wire you use is rated for the job.

regards,
james
 
jraef said:
No MTW that size. The problem with the extra flex cable, often called DLO (Deisel LOcomotive) cable is that the fine stranding cannot be used in mechanical lugs. The only approved termination method is to use special high pressure crimp lugs listed for that exact purpose, then use studs or bolts to terminate on the device, which of course implies that the device can accept that type of termination. If that works for you, by all means, use it. You just need to make sure the DLO has the dual rating as RHHW, not all brands do. Only the RHHW versions are UL listed.
Click to expand...

Sothwire seems to have a MTW that goes down to # 2 but maybe it's dual rating? http://www.southwire.com/products/MtwTewAwmIA.htm
 
I've used type W wire with good results, which is very fine stranded (dual rated and UL listed, so no problem there) and my local AHJ was fine with me using ferrules for the terminations. Crimp on the ferrule, place in terminal block.

-rpoet
 
Tim Ganz said:
I did not know the fine stranded stuff could not be used in mechanical lugs. We have a lot of panels that come from the OEM that way though. Is this in the NEC code book somewhere? I would like to have it for future reference.

THis wire is needed for 1 starter in 1 cabinet and to go from the disconnect terminals to the power distribution block which is 100 amp disconnect feeding the distribution block.

What is another choice more flexible than THHN?
Click to expand...
110.14, but you have to know what you are reading, it's not abundantly clear.
Connectors and terminals for conductors more finely
stranded than Class B and Class C stranding as shown in
Chapter 9, Table 10, shall be identified for the specific
conductor class or classes.
Click to expand...
Chapter 9 Table 10 shows that #2 wire is limited to 19 strands for class C (7 strands for Class B), so any wire with MORE than 19 strands, no matter what class it is (the table doesn't go higher), will nonetheless NOT be Class B or C, so unless the lugs are marked for a higher class, you cannot use them.

Once you get into the "extra flexible" hookup wire, like TEW, the manufacturers will have varying ways of stranding that can be anywhere from Class D (133 strands) to class K (665 strands).

From another forum you posted on, there is a link to a company that is now apparently selling a mechanical lug that says it is UL listed for "flexible" wire, but I have never seen them before, can't vouch for them. This page also lists the wire stranding classes though, which is useful.
http://www.ihiconnectors.com/Wire-Stranding-by-Class.htm
 
jraef said:
110.14, but you have to know what you are reading, it's not abundantly clear.

Chapter 9 Table 10 shows that #2 wire is limited to 19 strands for class C (7 strands for Class B), so any wire with MORE than 19 strands, no matter what class it is (the table doesn't go higher), will nonetheless NOT be Class B or C, so unless the lugs are marked for a higher class, you cannot use them.

Once you get into the "extra flexible" hookup wire, like TEW, the manufacturers will have varying ways of stranding that can be anywhere from Class D (133 strands) to class K (665 strands).

From another forum you posted on, there is a link to a company that is now apparently selling a mechanical lug that says it is UL listed for "flexible" wire, but I have never seen them before, can't vouch for them. This page also lists the wire stranding classes though, which is useful.
http://www.ihiconnectors.com/Wire-Stranding-by-Class.htm
Click to expand...

Jraef

Here are the distribution blocks I am using http://www.ab.com/en/epub/catalogs/12768/229240/229268/471156/Bul-1492-PDE-Enclosed-Style.html

It says "Flexible copper wire connections approved for flexible wire, stranding Classes G, H, I, K and DLO wire without the need for additional crimp connectors"

So I guess these are rated for the locomotive cable?
 
Tim Ganz said:
Jraef

It says "Flexible copper wire connections approved for flexible wire, stranding Classes G, H, I, K and DLO wire without the need for additional crimp connectors"

So I guess these are rated for the locomotive cable?
Click to expand...

That takes care of the entry, but what about the other connections?
 
Dang! In more than 35 years as an electrician and engineer I have never found THHN to be difficult to form. However if it's cold then that's a different story. BTW when it's cold out and the conductor jumps outta you hands and smacks your finger nail... well.. it is ok to sit down and bawl like a baby :)
 
LWCiak said:
Dang! In more than 35 years as an electrician and engineer I have never found THHN to be difficult to form. However if it's cold then that's a different story. BTW when it's cold out and the conductor jumps outta you hands and smacks your finger nail... well.. it is ok to sit down and bawl like a baby :)
Click to expand...

IMHO THHN is very dificult to form to the point it stays put when using it in a control panel and inside wire duct and it sounds like that's what the OP is doing with it.

That's why they make MTW and a few other types of flexible wire. THHN is building wire and made to pull through conduit. it's really not designed to be the first choice for in panel wiring.
 
regardless of code for each area, as a rule of thumb, if you have a screw terminal lug that the screw goes directly in contact with the wire, you need to use more rigid and less strands wires because tiny strands will jamm into the screw and make the screw feel tight when the wire remain loose. Some caged clamp connection are safe for tiny strands but the terminal would state it in it's specs
 

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