Single phase or Three Phase Breaker?

[uplanddreams]

Parking lot lighting is circuited 480 volt single phase. 2 hots each lamp AB BC CA. Nine circuits are used, grouped in three circuits to each run. Is the protecting breakers single phase breakers or 3 three phase breaker?

 

[LarryFine]

Are there handle ties?

 

[uplanddreams]

Not at this time.

 

[bdarnell]

These circuits need to be on 3 pole breakers.

 

[LarryFine]

I agree. Line-to-line loads must have all poles simultaneously interrupted.

I was being a wiseguy, responding to whether the breakers are 1- or 3-pole units, like they were already installed, rather than which ones should be installed.

never mind

 

[james wuebker]

These circuits need to be on 3 pole breakers.

Why do they need to be on 3 pole breakers? I know several companies that make 2 pole breakers for 480 volts.
Jim

 

[don_resqcapt19]

240.20(B)(3) 3-Phase and 2-Phase Systems For line-to-line loads in 4-wire, 3-phase systems or 5-wire, 2-phase systems having a grounded neutral and no conductor operating at a voltage greater than permitted in 210.6, individual single-pole circuit breakers with identified handle ties shall be permitted as the protection for each ungrounded conductor.

 

[LarryFine]

These circuits need to be on 3 pole breakers.

Why do they need to be on 3 pole breakers? I know several companies that make 2 pole breakers for 480 volts.

Because, unless I misunderstand the OP, each circuit is a 3-wire, with loads connected phase-to-phase, one on A-B, one on B-C, and one on C-A.

 

[oliver100]

If the project is on design phase, I would use one 3 phase breaker for the entire parking lot, running the 3 phase wires through each pole, tap it and protect each pole with 2 pole breaker or fuses.

Maintenance (re-lamping or repairs) would be safer and would not deprive the parking lot with group of not working lamps.

 

[Pierre C Belarge]

It seems to me the are 3 groups of 3, 2-pole circuits for the lights. In that case, a 2-pole breaker could be installed.

 

[james wuebker]

These circuits need to be on 3 pole breakers.

Why do they need to be on 3 pole breakers? I know several companies that make 2 pole breakers for 480 volts.

Because, unless I misunderstand the OP, each circuit is a 3-wire, with loads connected phase-to-phase, one on A-B, one on B-C, and one on C-A.

Larry, I believe it's 480 single phase that requires 2 hots and a grounding wire. He really didn't tell us how he was controlling these lights also.
Jim

 

[JES2727]

It seems to me the are 3 groups of 3, 2-pole circuits for the lights. In that case, a 2-pole breaker could be installed.

If they leave the panel as a 3-pole circuit and then split up downstream into three 2-pole circuits, how would you protect them each with a 2-pole breaker?


I agree with fine LarryFine. The only practical way to protect these conductors is with a 3-pole breaker.

 

[LarryFine]

I guess we need more info. Do the circuits leave the panel as 2-wire runs or 3-wire runs?

 

[celtic]

These circuits need to be on 3 pole breakers.

Why do they need to be on 3 pole breakers? I know several companies that make 2 pole breakers for 480 volts.
Jim

It is cheaper to run one 3-phase line and tap it as needed - using one 3-pole breaker, as opposed to running multiple lines and using 3 2-pole CBs.

I think "need" was a typo..correct me if I am wrong, bdarnell.

 

[peter d]

This brings up another issue. If the 3-pole breakers are used, do each of the lighting fixtures have individual fuse protection? A fault in any one of the circuits could easily knock out a large area of lighting.

 

[uplanddreams]

Thank you for your comments thus far. The 3 phase wire will be run from the breaker to a 3 pole contactor controlled by an EMS then to the parking lot poles. The phase conductors are tapped at each pole for the two phases needed. There is fuse protection for each phase conductor which runs up the pole to the lights.

 

[LarryFine]

Thank you for your comments thus far. The 3 phase wire will be run from the breaker to a 3 pole contactor controlled by an EMS then to the parking lot poles. The phase conductors are tapped at each pole for the two phases needed. There is fuse protection for each phase conductor which runs up the pole to the lights.

Definitely need a 3-pole breaker, since you have line-to-line loads.

This is not a multi-wire circuit; it's a single 3-phase circuit.

 

[don_resqcapt19]

Larry,

Definitely need a 3-pole breaker, since you have line-to-line loads.

Not if the supply system is grounded. See 240.20(B)(3).
dON

 

[LarryFine]

Larry,

Definitely need a 3-pole breaker, since you have line-to-line loads.

Not if the supply system is grounded. See 240.20(B)(3).
dON

I stand partially corrected: handle ties are permitted in both (B)(2) and (B)(3). The point is that simultaneous manual disconnecting is necessary, even if simultaneous automatic disconnecting is not.

I'm sure that we agree that, even though we and the NEC acknowledg the difference between the two, modern handle-tied breakers will, in fact, simultaneously trip from a single-phase over-current.

 

[don_resqcapt19]

Larry,

modern handle-tied breakers will, in fact, simultaneously trip from a single-phase over-current.

In most cases they will not trip the other pole(s).
Don