NEC 408.16( I ) Delta breakers
- Thread starter Gem Tan
- Start date
- Status
highkvoltage
Senior Member
Re: NEC 408.16( I ) Delta breakers
I do not what code version you are referring to I believe these are correct.
NEC 1999 Not in. 402.12 to 410 ??
NEC 2002 408.16(E)
NEC 2005 408.36(E)
Can not be installed in a single phase panel.
I do not what code version you are referring to I believe these are correct.
NEC 1999 Not in. 402.12 to 410 ??
NEC 2002 408.16(E)
NEC 2005 408.36(E)
Can not be installed in a single phase panel.
bphgravity
Senior Member
- Location
- Florida
Re: NEC 408.16( I ) Delta breakers
A delta breaker is a breaker that is designed to be installed on a single phase bus, but switch 3 conductors. One leg is a feed thru connection while the other two are fed from the bus. They are no longer permitted by code.
A delta breaker is a breaker that is designed to be installed on a single phase bus, but switch 3 conductors. One leg is a feed thru connection while the other two are fed from the bus. They are no longer permitted by code.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEC 408.16( I ) Delta breakers
Delta breakers have been prohibited by the NEC for almost 30 years. One problem with them was, the 3rd pole was not disconnected when the main on the panel was opened.
Delta breakers have been prohibited by the NEC for almost 30 years. One problem with them was, the 3rd pole was not disconnected when the main on the panel was opened.
sandsnow
Senior Member
- Location
- Southern California
Re: NEC 408.16( I ) Delta breakers
Delta breakers were used to install 120/240 volts 4-wire delta 3-phase in single phase panelboards. Originally, this was a 3-phase system that could be grafted onto existing 120/240 volts single phase.
The delta breakers were an early alternative to using separate single phase and 3-phase panels. Up here in Cleveland, Cleveland Public Power is still in the bad habit of connecting a 3-wire 3-phase service to a 4-wire wye or 4-wire delta system. One of the hazards is that pulling a form 12s 3-phase meter DOES NOT disconnect one of the hot leads. One of the other hazards is that the neutral in the lighting service is being used as the equipment ground of the 3-phase service. If either service uses steel conduit a ground fault in a 3-phase branch circuit WILL create a nasty tingle voltage as well as induction heating of the conduits.
The delta breakers were touted as safer because they allowed the utility to use one 4-wire meter such as a form 15s or 8s. Unfortunately, delta breakers were only "safe" if they were connected to the main bus of a spit bus panelboard. There was still the issue that multiple delta breakers were used with an add-on 3rd hot bus with wire terminals. This defeated the inherent safety of plug-in circuit breakers not to mention that there was no main disconnect for the 3rd hot bus.
Today, the better method is to use a small 3-phase main breaker panel and a 2-pole feeder breaker to feed the lighting panel. If you want to use two 100 amp service switches, 1 3-phase and 1 single phase, Milbank makes a terminal adapter for connecting two 100 amp wires per terminal in their 200 amp sockets. You can also do something similar with class 320 sockets using the right kind of box lugs to hook up two 200 amp service switches.
Delta breakers were used to install 120/240 volts 4-wire delta 3-phase in single phase panelboards. Originally, this was a 3-phase system that could be grafted onto existing 120/240 volts single phase.
The delta breakers were an early alternative to using separate single phase and 3-phase panels. Up here in Cleveland, Cleveland Public Power is still in the bad habit of connecting a 3-wire 3-phase service to a 4-wire wye or 4-wire delta system. One of the hazards is that pulling a form 12s 3-phase meter DOES NOT disconnect one of the hot leads. One of the other hazards is that the neutral in the lighting service is being used as the equipment ground of the 3-phase service. If either service uses steel conduit a ground fault in a 3-phase branch circuit WILL create a nasty tingle voltage as well as induction heating of the conduits.
The delta breakers were touted as safer because they allowed the utility to use one 4-wire meter such as a form 15s or 8s. Unfortunately, delta breakers were only "safe" if they were connected to the main bus of a spit bus panelboard. There was still the issue that multiple delta breakers were used with an add-on 3rd hot bus with wire terminals. This defeated the inherent safety of plug-in circuit breakers not to mention that there was no main disconnect for the 3rd hot bus.
Today, the better method is to use a small 3-phase main breaker panel and a 2-pole feeder breaker to feed the lighting panel. If you want to use two 100 amp service switches, 1 3-phase and 1 single phase, Milbank makes a terminal adapter for connecting two 100 amp wires per terminal in their 200 amp sockets. You can also do something similar with class 320 sockets using the right kind of box lugs to hook up two 200 amp service switches.
- Status