options for Switched neutral breakers

Status
Not open for further replies.
wwhitney said:
I don't see anything there prohibiting the use of a 3 bus panel for 120/240V plus neutral, seems like an elegant solution.

Cheers, Wayne
Click to expand...
110.3 (C) is all I've got.
I've actually done it. Didn't work out to good. Got turned down, but with a smile. He said nice try looks good, but nope.
But the AHJ could allow it.
 
LarryFine said:
What would have been a compliant installation?
Click to expand...
All I'm saying is I don't think it has been UL approved to have the grounded conductor terminated on the lug designed for a hot wire,
Are you following me?
He has a three phase panel. He wants to take the neutral from a single phase and put it on the middle phase of the three phase panel.
He wants to use a three phase breaker on single phase and wants the neutral on the third terminal. I'm referring to 110.3 (C)
So two items, the panel and the breaker would have to have been approved for that install.
 
Buck Parrish said:
110.3 (C) is all I've got.
I've actually done it. Didn't work out to good. Got turned down, but with a smile. He said nice try looks good, but nope.
Click to expand...
Bad call by the inspector.

In an ungrounded system, all circuit conductors will be disconnected by an OCPD, so they will all go to the busbars in a panel. In a grounded system, we usually take advantage of no longer needing to interrupt the grounded circuit conductor, so we use a terminal bar instead of a busbar. But nothing says we have to do that. The listing on a panel may impose a maximum voltage between the busbar and ground, but it certainly doesn't impose a minimum voltage.

240.22(1) tells us we can install OCPD on the grounded conductor when all circuit conductors are simultaneously opened by a common trip OCPD. To me, that says using a busbar for the grounded circuit conductor is allowed.

Cheers, Wayne
 
wwhitney said:
Bad call by the inspector.

In an ungrounded system, all circuit conductors will be disconnected by an OCPD, so they will all go to the busbars in a panel. In a grounded system, we usually take advantage of no longer needing to interrupt the grounded circuit conductor, so we use a terminal bar instead of a busbar. But nothing says we have to do that. The listing on a panel may impose a maximum voltage between the busbar and ground, but it certainly doesn't impose a minimum voltage.

240.22(1) tells us we can install OCPD on the grounded conductor when all circuit conductors are simultaneously opened by a common trip OCPD. To me, that says using a busbar for the grounded circuit conductor is allowed.

Cheers, Wayne
Click to expand...
OK , well there you go. Hope the OP is reading that. BTW Wayne, Have you used this option? Just wondering...
 
No, I'm not a practicing electrician. That means I'm often guided by reading the NEC itself, rather than received wisdom. That doesn't mean you won't find an AHJ who doesn't like the idea and isn't convinced by the citation I provided.

Cheers, Wayne
 
wwhitney said:
240.22(1) tells us we can install OCPD on the grounded conductor when all circuit conductors are simultaneously opened by a common trip OCPD. To me, that says using a busbar for the grounded circuit conductor is allowed.
Click to expand...
In addition, 404.2(B) Exception says:
"A switch or circuit breaker shall be permitted to disconnect a grounded circuit conductor where all circuit conductors are disconnected simultaneously ... "
 
Of course, those two references just tell you that you can use switched neutral breakers. They don't explicitly tell you that you do it via a regular multi-pole breaker with the neutral on one of the panel busses.

But absent anything specific that prohibits it, it is allowed. I don't believe the product standard for panelboards is going to require a minimum voltage between the busbars and ground, so 110.3(C) is no prohibition.

Cheers, Wayne
 
I don't recall ever seeing a panel instruction prohibiting grounded conductors on line terminals.

As long as it's as large as the other feeder conductor(s), it should be fine.
 
LarryFine said:
I don't recall ever seeing a panel instruction prohibiting grounded conductors on line terminals.

As long as it's as large as the other feeder conductor(s), it should be fine.
Click to expand...
I would/could use them on a three phase grounded delta system and be perfectly legal. There is no difference other than the application to single phase, however, I would not surprise my AHJ. They may be wrong in their interpretation but way cheaper to have the discussion before the installation.
 
ptonsparky said:
I would/could use them on a three phase grounded delta system and be perfectly legal.
Click to expand...
Can you use a single phase panel (I should say two bus bar panel) on a three phase grounded delta, with the grounded conductor on the "neutral" bar? If not, why not?

I can see a voltage to ground issue, if single phase panels aren't available with a sufficiently high voltage to ground rating, but I'm curious if there's any other issue. Also, if you wanted to balance your single phase L-L loads evenly, one third (VA wise) of them would need to originate from double pole breakers.

Cheers, Wayne
 
I have used a contactor to cover the "switched neutral" requirements for C1D1 dispenser circuits. Hot and neutral of the circuit leave the panel and go to L1 and L2 of the contactor and jump to coils of the contactor. The L and N of the dispenser circuit land on the output of the contactor. Turn off the single-pole breaker and the contactor drops out breaking both hot and neutral.

For years I've wanted to try the feeding a panel with L and N and using 2-pole breakers but I never wanted to risk doing it w/out prior approval and I never found an AHJ that would stick their neck out.

Too many lawyers needing work is not good for our society.
 
ptonsparky said:
The standard plug on CH 3 phase panel I have on my shelf is 208Y/120 VAC. Can't use that one.
Click to expand...
I didn't track down the actual Eaton catalog, but this webpage (near the bottom) says that the CH 3 phase panels are "Three-Phase Four-Wire--208Y/120 Vac or 240 Vac Insulated/Bondable Split Neutral". Not 100% sure what the last part means, but pretty sure it means that 240V between busbars is OK, you're not limited to 208V.

www.eaton.com

CH Loadcenters

Eaton’s CH 3/4-inch loadcenters enclose CH circuit breakers for power distribution and protection in residential and light commercial applications. They are used on services providing no more than 240 Vac and are available with bus rated 40-600A.
www.eaton.com www.eaton.com

Cheers, Wayne
 
LarryFine said:
I think it refers to two neutral bars, joined by a removable link, and bonding it/them is optional.
Click to expand...
Now that I look at it again, the single phase panels are labeled "Single-Phase Three-Wire--120/240 Vac--Insulated/Bondable Single Neutral".

So the "insulated/bondable" definitely refers to a bonding jumper/screw. But I think that "split neutral" vs "single neutral" probably refers to using one of the bus bars for a grounded conductor.

Cheers, Wayne
 
You see this at most any gas/fuel station. The panel neutral is switched only for fuel panel. I know CUtler hammer has a 2pole switch neutral breaker where you dont need to modify panel at all. The neutral feeds through breaker similar to AFCI breaker but makes no contact with buss. Just FYI.
 
Some circuit breakers can have an aux switch added to them.
We used to build panels for fuel dispensing and they just used relays for this function.
 
Status
Not open for further replies.
Top