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[Rob Spence]

That's quite helpful, Tim. Thank you. Two follow-on q's which I know will be a cakewalk for you LOL ---

• How does this sound? "50A split-phase 110V phase-to-neutral, 3 wires plus ground, 4 wires total, for connecting a tail set or an L5-50P."  ....or did I get too wordy?
• Forgive my ignorance, must the two hot conductors always be fed from separate lines of the split-phase, or may they draw from the same phase if the individual upstream breakers equal each conductor's ampacity?

Just say what Tim said.

120/240 50a 4 wire. 3 wires plus ground.

Use all the words as written. Don't get cute with it.

Since you said lugs, don't confuse it with connector types.

Go study a NEMA chart so you get your designations right. Your lack of knowledge about even what connectors to use is scary.




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[Rob Spence]

I note that the various posters used 110, 120 and 125 (and the associated double).

As far as I know, 110 has fallen out of common usage and while NEMA identifies connectors as 125/250, the most seen usage seems to be 120/240.

Comments?

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[Timothy J. Trace]

Just say what Tim said. 120/240 50a 4 wire. 3 wires plus ground. Use all the words as written. Don't get cute with it. Since you said lugs, don't confuse it with connector types.

Fair enough. Respectfully, no one has yet used the word "lugs," except me. Is that the correct term to use which should be understood by a commercial electrician in this context, "lugs?"

Go study a NEMA chart so you get your designations right. Your lack of knowledge about even what connectors to use is scary.

I did, Rob. Right here: http://www.stayonline.com/reference-nema-locking.aspx ...and became confused, which serves as an explanation as to why I'm here seeking assistance.

ETA: And now, thanks to Mark's help, I see the NEMA L14-50 on that chart and the cross-ref to the CS6365C. Nice!

[Andrew Broughton]

Thanks. Can you help me understand how this is different than having two branch circuits drawing off the same line? Is it because we're dealing with portable distribution?

I'll leave that to the experts, but it would be necessary in the case that the 2 hots were being tied into 2 50a breakers on the same phase. If you tied both conductors into 1 50a breaker, you'd probably be fine (someone can correct me if I'm wrong), but you'd only be able to draw 1/2 the amperage that you would if the 2 hots were on opposite phases.
Tying the 2 hots into anything larger than a 50a breaker of course would still be illegal.

[Tim McCulloch]

That's quite helpful, Tim. Thank you. Two follow-on q's which I know will be a cakewalk for you LOL ---

• How does this sound? "50A split-phase 110V phase-to-neutral, 3 wires plus ground, 4 wires total, for connecting a tail set or an L5-50P."  ....or did I get too wordy?
• Forgive my ignorance, must the two hot conductors always be fed from separate lines of the split-phase, or may they draw from the same phase if the individual upstream breakers equal each conductor's ampacity?

"50A 120/240v split (aka single) phase, 3 wires plus ground, terminated to Hubbell CS6369 or to lugs in a fused disconnect switch."

When you specify 120/240v service it requires (or at least infers) that the 2 hot legs are 180° apart, with the center tap acting as Neutral.

[Timothy J. Trace]

"50A 120/240v split (aka single) phase, 3 wires plus ground, terminated to Hubbell CS6369 or to lugs in a fused disconnect switch."

When you specify 120/240v service it requires (or at least infers) that the 2 hot legs are 180° apart, with the center tap acting as Neutral.

Thanks, Tim. Does "fused" include enclosed circuit breaker disconnects by implication?

[Stephen Swaffer]

50 amp 120/240v single phase with ground (3 wires plus ground, 4 wires total).

I've found that non-entertainment electricians do not consider the EGC to be "a wire".  The 120/240v designation SHOULD tell the electrician that we want split-phase, not 240v service.

When specifying 3 phase power I've found it necessary to call out WYE service, as in "200 amp 120/208v 3 phase wye, 4 wires plus ground (5 wires total)."

+1

FWIW, as an electrician the context is important.  3 phase/4 wire when talking a panel or service implies 3 phases plus a neutral-because 3 phases without a neutral is common in industry.  When dealing with portable cord 3 phase 4 wire implies 3 phases plus a ground because we are usually dealing with a 3 phase load.  So the context determines whether or not a wire is "counted".  Why make it easy?  So yes all of the wording is important.

I would prefer to see "breaker or fused disconnect" just because there times where fuses (specifically fast blow) are mandated so while a breaker and a fuse are both acceptable by code for overcurrent protection they are not always equivalent so tell me its "OK". 

[Frank DeWitt]

Your lack of knowledge about even what connectors to use is scary.

It is good that he is gaining knowledge.  I am much more worried about people who don't want to learn.

[Mike Sokol]

"50A 120/240v split (aka single) phase, 3 wires plus ground, terminated to Hubbell CS6369 or to lugs in a fused disconnect switch."

When you specify 120/240v service it requires (or at least infers) that the 2 hot legs are 180° apart, with the center tap acting as Neutral.

Actually, in addition to 180 degree phases, the latest code revision allows you to connect an RV plug to 2 hot legs that are 120 degrees out of phase, basically 2 legs of a 3-phase Wye service. But as you stated, you can't use the same phase to feed both legs. That's because the neutral current will then be additive rather than subtractive. Basically, if you feed both legs of the plug with a common phase, then you can easily get 60, 70, 80 or even 100 amps flowing though a neutral wire and connection only rated for 50 amps.

Here's what a 50-amp NEMA 14-50 plug looks like when its neutral tried to carry more than 50 amps due to both hot legs being connected to the same phase. It ain't pretty...

[Timothy J. Trace]

Basically, if you feed both legs of the plug with a common phase, then you can easily get 60, 70, 80 or even 100 amps flowing though a neutral wire and connection only rated for 50 amps.

Thanks,  Mike!

[ProSoundWeb Community]