Common trip required on ungrounded systems {interpretation}. See 240.15(B), and (2) thereunder.If I have a single phase 460V (460V line to line) load, is there any reason to use a double pole circuit breaker over a single pole breaker?
240.15 Ungrounded Conductors.
(B) Circuit Breaker as Overcurrent Device. Circuit breakers
shall open all ungrounded conductors of the circuit both
manually and automatically unless otherwise permitted in
240.15(B)(1), (B)(2), (B)(3), and (B)(4).
Common trip required on ungrounded systems
As opposed to singular form, system?Typo?
As opposed to singular form, system?
I think either can be used in the vernacular of my reply... but if I drop the s, then I have to insert an an before ungrounded.
Note the requirement for automatically in 240.15(B) general statement. Item (2) thereunder provides exception for grounded systems, which means breakers can be independent trip. Ergo, no exception for ungrounded systems. OP did not mention whether load is going to be connected to grounded or ungrounded system.Than I am curious why you assume an ungrounded system. I thought you meant to type ungrounded conductors.
A solidly bonded Wye system often supplies single phase 480 line to line loads. The OP mentioned loads while you are mentioning systems.
Seems we need more info.
Note the requirement for automatically in 240.15(B) general statement. Item (2) thereunder provides exception for grounded systems. Ergo, no exception for ungrounded systems.
Added last sentence to my post as you replied...And still I am not understanding why you are assuming it is an ungrounded system.
It may well be an ungrounded system I just don't see anything from the OP pointing that way.
I will wait for the OP to chime in.
To be clear, you are connecting to a [grounded] 480Y/277V 3? 4W system, right? A 460V system is non-standard, but it is a common rating on NEMA equipment for a load to be connected to a 480V source. Some non-NEMA equipment manufacturers mimic that NEMA rating.It is a 460Y VAC system.."circuit breaker must open all ungrounded conductors" is pretty clear, I will use double poles for these loads
You can break only one pole, but common industry practice is to break both concurrently.Is there anything similar for relays and contactors? Can I control a single phase motor, that is powered from 230V transformer, ungrounded (though the 115V center tap is ground) with a single pole from a relay, or would I need to open/close both ungrounded conductors?
It is a 460Y VAC system.."circuit breaker must open all ungrounded conductors" is pretty clear, I will use double poles for these loads
Is there anything similar for relays and contactors? Can I control a single phase motor, that is powered from 230V transformer, ungrounded (though the 115V center tap is ground) with a single pole from a relay, or would I need to open/close both ungrounded conductors?
You can do whatever makes the motor stop and start. The breaker (or fuse) is about protection. The contactor has nothing to do with PROTECTION of the circuit, only control of it.It is a 460Y VAC system.."circuit breaker must open all ungrounded conductors" is pretty clear, I will use double poles for these loads
Is there anything similar for relays and contactors? Can I control a single phase motor, that is powered from 230V transformer, ungrounded (though the 115V center tap is ground) with a single pole from a relay, or would I need to open/close both ungrounded conductors?
It is a 460Y VAC system.."circuit breaker must open all ungrounded conductors" is pretty clear, I will use double poles for these loads
Is there anything similar for relays and contactors? Can I control a single phase motor, that is powered from 230V transformer, ungrounded (though the 115V center tap is ground) with a single pole from a relay, or would I need to open/close both ungrounded conductors?
An overload relay on a motor circuit is similar, but not exactly the same. So for example if you use an external OL relay on a single phase motor fed with 2 ungrounded conductors (i.e. L1, L2), you must have an OL sensing elements in EACH ungrounded conductor.
Only if you want to kill somebody.