Different voltages spliced in same box

[slalom skier]

A few of the Foreman at work are stating you can not splice both 120 and 277 in the same box I can not find any thing in the code book that says you can not do this. If it is a violation what code article would it be?

 

[roger]

They are wrong, tell them they need to read 300.3(C)(1)

Roger

 

[cadpoint]

It's not so much that you can splice the joints, it's the sum of the voltage in the box that causes the problem, it's 250V between conducts, you need separtation in the box!
I'm not sitting with a book!

 

[slalom skier]

It's not so much that you can splice the joints, it's the sum of the voltage in the box that causes the problem, it's 250V between conducts, you need separtation in the box!
I'm not sitting with a book!

Doesn't that apply just to switches?

 

[roger]

It's not so much that you can splice the joints, it's the sum of the voltage in the box that causes the problem, it's 250V between conducts, you need separtation in the box!
I'm not sitting with a book!

Jude, it's 300 volts.

Roger

 

[cadpoint]

Damn it!

 

[infinity]

Doesn't that apply just to switches?

Yes.

 

[don_resqcapt19]

Yes.

I think you are a couple of cycles behind. 406.4(G) in 2008 or 406.5(G) in the 2011.

 

[infinity]

I think you are a couple of cycles behind. 406.4(G) in 2008 or 406.5(G) in the 2011.

Oops, yes you're right it applies to devices not only switches. :happyyes:

 

[hillbilly1]

Jude, it's 300 volts.

Roger

I have to take issue with that drawing, I may be missing something here, but since the 277 and 120 are separately derived systems, the voltage shown with the meter should not be the total of the two. Funny thing is in the 32 years of being an electrician, I don't remember ever checking between a 120 volt circuit and a 277 volt circuit. Looks like I got a project Monday morning. (and I probably just opened up a big can of worms that needs another thread)

 

[infinity]

I have to take issue with that drawing, I may be missing something here, but since the 277 and 120 are separately derived systems, the voltage shown with the meter should not be the total of the two. Funny thing is in the 32 years of being an electrician, I don't remember ever checking between a 120 volt circuit and a 277 volt circuit. Looks like I got a project Monday morning. (and I probably just opened up a big can of worms that needs another thread)

There is a theoretical condition where, depending on the phasing, that the same two devices can have less than 300 volts between them. Maybe an engineer can explain it.

 

[roger]

See the threads below.
http://forums.mikeholt.com/showthread.php?t=86550&highlight=404.8(B)

http://forums.mikeholt.com/showthread.php?t=117602&pag


http://forums.mikeholt.com/showthread.php?t=82918

Roger

 

[Hv&Lv]

I scanned over the threads and noticed that they say both systems come from seperatly derived three phase systems. How about a 277/480 three phase system and a single phase 240/120 system?

 

[don_resqcapt19]

I scanned over the threads and noticed that they say both systems come from seperatly derived three phase systems. How about a 277/480 three phase system and a single phase 240/120 system?

What would be the phase angle between the voltages on the two systems? Once you have that you use the law of cosines or other method of vetor addition to find the voltage between the two.

 

[acrwc10]

You have all missed the forest while examing one tree. The OP said "splice differing voltages in the same box" not "Devices in the same box".
While you are correct you can not have the shown voltages on a device, in a box with switches and receptacles. You can SPLICE wires in the box, as long as the insulation on all the conductors is suitable for the to the highest voltage in the box. Since most wire used has a 600volt rating, if you have a J-box with 120 and 277/480 being spiced and then run to where ever, your good to go.

 

[roger]

You have all missed the forest while examing one tree. The OP said "splice differing voltages in the same box" not "Devices in the same box".
While you are correct you can not have the shown voltages on a device, in a box with switches and receptacles. You can SPLICE wires in the box, as long as the insulation on all the conductors is suitable for the to the highest voltage in the box. Since most wire used has a 600volt rating, if you have a J-box with 120 and 277/480 being spiced and then run to where ever, your good to go.

See post #2

Roger

 

[acrwc10]

See post #2

Roger

Sorry Roger, I did and almost noted it. It was all the drawings that made me throw you under the bus too.:lol:

 

[roger]

Sorry Roger, I did and almost noted it. It was all the drawings that made me throw you under the bus too.:lol:

That's OK, I becoming pretty familiar with the undercarriage of the bus from people I work with.

Roger

 

[kwired]

Sorry Roger, I did and almost noted it. It was all the drawings that made me throw you under the bus too.:lol:

All the drawings were an attempt to clarify what was incorrectly introduced in post #3. Post 3 was not really off topic but was incorrect information that could be taken as it was written to apply to OP.

 

[acrwc10]

All the drawings were an attempt to clarify what was incorrectly introduced in post #3. Post 3 was not really off topic but was incorrect information that could be taken as it was written to apply to OP.

I agree, when a question is posted I think every angle need be looked at. I just wanted to clearify the most obvious to the OP. His "teachers/supervisors" were saying "you can't", when in some cases "you can" and he didn't say if it was in a j-box or a switch box so all points were valid.