National Electrical Installation Standards

Standards as High as Your Own

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Monday, October 22, 2018

Question:

I'm an electrician for the government and I been fighting this issue with our building manager and a project manager about multi branch circuits. They have been installed and are used to supply power to nonlinear loads to lighting and also receptacles which feed medical equipment. They have allowed electrical contractors to use 3 ungrounded conductors and one shared neutral from a 4 wire 3 Phase systems using 3 pole type breakers sharing one neutral. Violation of article 410.130(G)(2) none of the neutral conductors have a disconnection means. This was back in 2011, but they still continue to allow this practice, the electrical contractor has stipulated that the installation are in no way in violations to the NEC. So even though 225.33(B), 230.71(B) and 240.15(B), permit two or three single-pole switches or breakers on the multiwire branch circuits that are capable of individual operation—one pole for each ungrounded conductor and one multipole disconnect—provided these devices are equipped with identified handle ties or a master handle to disconnect all ungrounded conductors. Does that mean that’s its ok to use a three pole breakers, with ties, marked in accordance to the code to be use to feed lighting and receptacle circuits that use 3 ungrounded conductors and a share a neutral. Most of the buildings are medical in natural, 3 are dental clinics that do provide surgical care and main building was a hospital but was reduced to clinical services now. Thanks any help to explain if this practice of using a multi branch circuit is still in accordance with new 2017 NEC standards and was this practice allowed back in 2011

Adolfo Munoz

A

Answer:

Hey Adolfo thanks for your question and your concern for safety. In the 2002 NEC multiwire branch circuits (as they are defined in Article 100) supplying more than one device or equipment on the same yoke had to have a means to simultaneously disconnect all ungrounded conductors of the circuit at the panelboard for dwelling units as stated in 210.4(B). That section was changed in the 2005 NEC to remove the dwelling only applicability and the simultaneous disconnecting means was to be located where the branch circuit originated. For the 2008 NEC that section was again changed to remove the words " more than one device or equipment on the same yoke" so all multiwire branch circuits require a means to simultaneously disconnect all ungrounded conductors.

Section 410.73(G) was added in the 2005 NEC to require indoor fluorescent luminaires ballasts to have a means to simultaneously disconnect all conductors of the ballast including grounded conductors with an effective date of January 1, 2008. That section was changed and relocated to 410.130(G) as part of the reorganization of Article 410 for the 2008 NEC. There are products readily available for this purpose,

Articles 225 and 230 do not apply to your example because they are for branch circuits and feeders or services - that supply buildings or structures.

Multi-wire branch circuits (shared neutral) are allowed if all the rules are followed. You will need to find out when (or if being you are government) the 2008 NEC was adopted in your area. You don't mention voltages but 240.15(B) applies to multiwire branch circuits and 410.130(G) applies to specific types of luminaires. Notice that disconnecting means must be installed if ballasts are replaced in existing installations.

Finally branch circuits supplying receptacles at patient bed locations in both general care and critical care cannot be supplied by multiwire branch circuits as stated in 517.18(A) and 517.19(A).

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