ETC unison wiring with a thhn free air?

Sra328

New User
Location
Boston
Occupation
Project Manager
Looking for suggestions specifically for cable type U, debating with colleague whether the #14 shown alongside belden 8471 can be a thhn pulled with the belden, or if it needs to be a 14awg within a cable. All on j hooks/metal stud bushings, no conduit. I don’t believe 250.64 applies.
The purpose of the 14 awg is to discharge any static when a user touches the low voltage control stations.
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hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
debating with colleague whether the #14 shown alongside belden 8471 can be a thhn pulled with the belden, or if it needs to be a 14awg within a cable. All on j hooks/metal stud bushings, no conduit. I don’t believe 250.64 applies.
The purpose of the 14 awg is to discharge any static when a user touches the low voltage control stations.

THHN by itself is fine. Besides, I don't think you will find a one conductor #14 cable.

-Hal
 

SceneryDriver

Senior Member
Location
NJ
Occupation
Electrical and Automation Designer
ETC was always super weird about insisting on the #14 ground wire everywhere. Even when the button station cable was in conduit. No one at ETC's tech support could ever explain the actual purpose of the separate ground wire and what it did differently than the shield on the cable and/or conduit, but that was always the first thing they asked about if you called to troubleshoot a Unison system's button stations. I'd reach out to tech support at ETC if you have questions. That way you're covered, warranty-wise.

It's funny that Unison systems are still being installed this way. I just ripped out a Unison houselight/worklight control system wired exactly like this at a theater, as all the button stations had fallen apart - stagehands are hard on equipment.


SceneryDriver
 
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