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Thread: SE panel - breakers
10-30-2007, 09:37 AM #1
10-30-2007, 09:44 AM #2
10-31-2007, 07:07 PM #3
Re: SE panel - breakers
Connecting each ungrounded conductor supplying power to a device by using a seperate breaker for each ungrounded conductor WILL allow the device to work, but the practice is UNSAFE. The purpose of the NEC is to ensure that electrical systems are installed in a manner that protects people and property by minimizing the risks associated with the use of electricity (see Article 90.1).
10-31-2007, 07:23 PM #4
Re: SE panel - breakers
From the 2005 NEC. (underlining is mine)
240.20 Ungrounded Conductors.
- (B) Circuit Breaker as Overcurrent Device. Circuit breakers shall open all ungrounded conductors of the circuit unless otherwise permitted in 240.20(B)(1), (B)(2), and (B)(3). (Jerry's note: None of the exceptions apply to what is shown.)
- - (1) Multiwire Branch Circuit. Except where limited by 210.4(B), individual single-pole circuit breakers, with or without approved handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.
- - (2) Grounded Single-Phase and 3-wire dc Circuits. In grounded systems, individual single-pole circuit breakers with approved handle ties shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads for single-phase circuits or 3-wire, direct-current circuits.
- - (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 approved handle ties shall be permitted as the protection for each ungrounded conductor.
The end result, though, is the same as what Mike posted, "The bottom line is this - To ensure that the power to a device is completely "OFF", ... ", i.e., each ungrounded conductor has power removed by either common trip breakers or handle ties between separate breakers.
By the way - don't forget that the white conductor should not be "white", it is required to be "permanently reidentified by painting" (not tape) to a color other than white, green, or gray, i.e., black, red, brown, etc.