Meeks484

Wire size <18awg

5 posts in this topic

I design my wire sizes according to its protection. If it's fused at three amps, I'll use 22 awg for whatever the application is. My coworker recently told me im supposed to use at least 18 awg for everything but communication. Is this true? If so where is it referenced in nfpa79? Thanks. 

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That's probably a state level electrical code.
Some states have gone nuts with their electrical codes. Maryland requires 12ga on anything over 60 volts excluding prefabricated assemblies. 
This gets to be real fun with some 4 wire analog transmitters and a real nightmare with Hach sc200 controllers.

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When I worked in a panel shop and did machine wiring (converting machines etc.) these were our rule of thumb standards.

I do not know if  they were code but common standards.

Was 10 years ago or more

Control 120 wiring red 16 AWG mtw in the cabinet

Control 120 wiring red 14 AWG thhn in the on the machine

Analog wiring 18 AWG shielded in the cabinet & on the machine

Power wiring Motors etc black 12 AWG thhnshielded in the cabinet & on the machine

DC control  wiring blue 16 AWG mtw in the cabinet

DC control  wiring blue 16 AWG thhn on the machine

in my opinion 22 AWG can be pain in the a** to work with.  It's flimsy & can tend to break when stripping

Keep the guys doing the wiring happy (within reason of course)

The above is one guys opinion only 

 

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Not sure about the codes, but as an Electrician/Technician/Engineer/ProjectManager over past 35 years I prefer the wire to be larger than needed.  Running 12/14 where 18 is needed leaves you with the option to expand without running new wiring.  Not a code thing just a practicality thought.

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