MTW wiring

[kwired]

So just to throw this out there. GE afcis have the neutral tail made out of MTW and that's all it says for insulation type. Idk if UL considers a panel a machine and yes it isn't pulled in conduit but it does show a separate respected entity accepting a use for that wire where not installed in a piece of machinery or in a whip to a piece of machinery.

That breaker is listed as is though. If you had to supply that lead in the field that might be different as far as what you can or can't use for it.

Some those GFCI's and AFCI's even have smaller conductor for this pigtail than what you might use if you were field installing them.

 

[letgomywago]

That breaker is listed as is though. If you had to supply that lead in the field that might be different as far as what you can or can't use for it.

Some those GFCI's and AFCI's even have smaller conductor for this pigtail than what you might use if you were field installing them.

So if someone finds a surge arrestor that uses MTW and that includes in its instructions for flush install use of liquid tight conduit connecting it to the device before connecting to the panel would this discussion be more in favor of MTW being allowed in conduit?

 

[kwired]

So if someone finds a surge arrestor that uses MTW and that includes in its instructions for flush install use of liquid tight conduit connecting it to the device before connecting to the panel would this discussion be more in favor of MTW being allowed in conduit?

Most of devices you are talking about here are designed to insert into a KO in an enclosure and then make connections inside that enclosure. Unless leads are rather long wouldn't be all that practical to even do what I think you are suggesting.

 

[letgomywago]

Most of devices you are talking about here are designed to insert into a KO in an enclosure and then make connections inside that enclosure. Unless leads are rather long wouldn't be all that practical to even do what I think you are suggesting.

Look up Square D flush install kit for their residential SPD. Either it's TW or MTW I can't remember what the leads are but it has a flush mount kit that is from square D that is just 2 liquid tight connectors, a drywall anchor with mounting plate, and a rigid coupling.

 

[letgomywago]

Look up Square D flush install kit for their residential SPD. Either it's TW or MTW I can't remember what the leads are but it has a flush mount kit that is from square D that is just 2 liquid tight connectors, a drywall anchor with mounting plate, and a rigid coupling.

The leads are about 18 inches long.

 

[Todd0x1]

So if someone finds a surge arrestor that uses MTW and that includes in its instructions for flush install use of liquid tight conduit connecting it to the device before connecting to the panel would this discussion be more in favor of MTW being allowed in conduit?

I'd say no considering the device is listed and the instructions saying to use conduit would be covered by the listing.

 

[winnie]

The questions in my mind are:

1) Is there permission in the code to use MTW as building wire? IMHO no, because the 'uses permitted' for MTW are limited to wire in equipment.

2) Is this restriction archaic, based on prior construction of this type of wire? Plausible. Old rubber insulation materials had far more tradeoffs then current materials.

3) Are common 'MTW' conductors of the type the OP wants to use 'dual rated' with another type that is explicitly permitted for building wire? Most common stranded THHN is also rated THWN and MTW... but this wire doesn't have the fine stranding the OP wants. Perhaps all MTW one buys today has another rating that renders this discussion academic.

Jon

 

[Todd0x1]

The questions in my mind are:

3) Are common 'MTW' conductors of the type the OP wants to use 'dual rated' with another type that is explicitly permitted for building wire? Most common stranded THHN is also rated THWN and MTW... but this wire doesn't have the fine stranding the OP wants. Perhaps all MTW one buys today has another rating that renders this discussion academic.

There are several manufacturers which have MTW with the fine stranding with multiple listings on it. Usually MTW, TEW and one or more AWM numbers, sometimes even boat wire ratings as well.

I just went and looked at some AWM I use and it has the additional markings of MTW and THHW its 6ga fine strand tinned copper.