3W for 2W

[Alwayslearningelec]

So I'm doing a temp install and need to run 2 hots + neutral cable from xfrmr to disconnect switch.
My vendor can only get this cable with 3 hots + neutral. Can I still run this cable and only use 2 of the phase conductors?

Not using pipe/conduit and wire.

Thanks

 

[Tulsa Electrician]

Not using a SSBJ?

 

[Alwayslearningelec]

Not using a SSBJ

I can use the neutral for that, correct?

 

[electrofelon]

Sounds like this is an electrical service from a utility transformer? If so yes three conductors are fine you can leave one conductor unused if that's what the cable has.

 

[Tulsa Electrician]

Thought it was that temp set up for the trailers you were working on. Sorry

 

[zbang]

An extra unused conductor is seldom an issue except for conduit/box fill and pulling.

 

[augie47]

If this is your ongoing "construction trailer" install, you need a total of 4 conductors,,L-L-N-SSBJ so you can use the "spare" wire as your SSBJ.
If it's a utility transformer just ignore the extra conductor.

 

[Alwayslearningelec]

If this is your ongoing "construction trailer" install, you need a total of 4 conductors,,L-L-N-SSBJ so you can use the "spare" wire as your SSBJ.
If it's a utility transformer just ignore the extra conductor.

View attachment 2563127

Oh wow. I didn't realize secondary side of xfrmrs( not utility) need the hots, neutral and SSBJ.
I believe all I've seen on drawings has always been just the hots and neutrals.

 

[augie47]

Oh wow. I didn't realize secondary side of xfrmrs( not utility) need the hots, neutral and SSBJ.
I believe all I've seen on drawings has always been just the hots and neutrals.

Most of yoru drawings are likely conduit systems where the metallic conduit is one of the conductors.

 

[Alwayslearningelec]

Most of yoru drawings are likely conduit systems where the metallic conduit is one of the conductors.

corrrect. Guys use the conduit as an EGC all the time. It can be used as a SSBJ as well?

 

[augie47]

You might want to review 250.30 concerning Separately Derived System grounding.
In regard to the SSBJ see 250.30(A)(2)
"The supply-side bonding jumper shall be permit‐ ted to be of nonflexible metal raceway type or of the wire or bus type as follows:..........."

 

[electrofelon]

Also note there is an allowance to use the grounded conductor as the bonding conductor (like a service) where an outdoor transformer is used. It is possibly that's what you have seen.

 

[Tulsa Electrician]

Key words:
permit‐ ted to be of nonflexible metal raceway

If you use EMT and have a short pieces of flex an SSBJ is required.

 

[Alwayslearningelec]

what if mc cable was used?

 

[Tulsa Electrician]

As long as the wire used for the SSBJ with in the cable is of the correct size.

 

[augie47]

As long as the wire used for the SSBJ with in the cable is of the correct size.

That's a good point ! In all likelihood it would not be since its' sized 250.122 and the SSBJ is 250.66.

 

[Alwayslearningelec]

I’m sire people have run mc from secondary side of xfmr . I’m my case it’s temp . I only need 2 phase conductors but since I need a SSBJ along with the neutral I CANT get MC with 2 hots a neutral and full size ground ?? The there would be no SSBJ. Guess I should get MC with 3 hots and use one as SSBJ if sized accordingly . Or maybe just ignore the SSBJ..jk.

 

[LarryFine]

Could you use SER?

 

[augie47]

Seemingly a lesson in futility. You stated you didn't want to use conduit but you are willing to rig" SE or MC, etc. IF you can use MC I can't think of any logical reason you can't use FMC, LFMN, LFNMC,, etc and just install the proper individual conductors rather than reconfigure a cable and reinventing the wheel.
A qualified journeyman would have this installed to Code in the time we've spent talking about it.

 

[Alwayslearningelec]

Could you use SER?

No they just denied the use. they want us to use MC cable and splice to SER when we penetrate the wall going outside.