Modular furniture disconnects

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iwire

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Staff member
Location
Massachusetts
When wiring modular furniture how do meet the 210.4b disconnect requirements without a 4 pole breaker tie.

You will never need a four pole even if you have furniture that uses four breakers.

At most you would need to tie three breakers together.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Because of the hazards associated with non linear loads and shared neutrals, some modular furniture is wired for two hots (two of the three phase conductors) sharing one neutral and the third phase wire, designated for computers, with its own separate neutral.
That does not completely deal with harmonics on the shared neutral, and it makes both neutrals count as CCCs, but it greatly reduces the potential problems.
 

MCE001

Member
Location
detroit MI USA
the system being used is a 3+1 system, 3 ckts to 1 neutral and grd and 1 ckt with a dedicated neutral and dedicated ground. 210.b4 states all multi ckt branch wiring must be disconnected from a single point. Is the modular wiring harness for the furniture considered a a multiwire branch ckt?
 

jumper

Senior Member
the system being used is a 3+1 system, 3 ckts to 1 neutral and grd and 1 ckt with a dedicated neutral and dedicated ground. 210.b4 states all multi ckt branch wiring must be disconnected from a single point. Is the modular wiring harness for the furniture considered a a multiwire branch ckt?

The harness is not a MWBC, your "3 ckts to 1 neutral and grd" is and needs a handle tie
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
This may help from NEC Article 100:

Branch Circuit, Multiwire. A branch circuit that consists
of two or more ungrounded conductors that have a voltage
between them, and a grounded conductor that has equal
voltage between it and each ungrounded conductor of the
circuit and that is connected to the neutral or grounded
conductor of the system.
 
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