Wire size <18awg

[Meeks484]

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. 

[NevergoldMel]

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.

[Meeks484]

Thanks for the response. 

[jimtech67]

 

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 thhn 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 

 

Edited June 7, 2021 by jimtech67

[BobLfoot]

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.

[Mackemma]

In fact, it is very important to approach this issue responsibly, as it is very dangerous. Electrical wiring is the most important artery of the entire energy supply system of the house. Since the old electrical networks are not designed to work with modern more powerful household equipment, in order to avoid the risks of heating the wires or short-circuiting, it is recommended to completely replace the wiring in accordance with the established standards and safety requirements. Contact a Level 2 Electrician Liverpool electrician. They know very well how to do their job. I can confidently recommend it to you!

Edited June 18, 2021 by Mackemma

[pturmel]

The U.S. National Electric Code is very specific about ampacities for various conductor sizes and installation conditions.  There must be fuses/circuit breakers placed to ensure wires are protected from overcurrent.  Use small wires at your peril.

That said, you must also ensure you don't put too large a wire into some connectors.  Small spring-clamps on some PLCs don't accept wire larger than 16awg, and work best with 18awg.  Be sure your circuits have the necessary protection in such cases.

[WattUp]

UL508 : Standard for Safety of electrical control panels. 

Quote

The size of insulated conductors inside an industrial control panel cannot be smaller than 14 AWG. Actually, for Industrial Machineries, for low rated power motors, even size of conductors smaller than AWG 14 can be used inside the control panel (Table 66.1A).