Return to the Electrical Wiring Forum | Post a Follow-Up

Fusible Switch Circuit

Posted by ezridermn (My Page) on
Wed, Feb 2, 11 at 9:12


I want to wire an electrical circuit in my home to run a small Miller TIG welder. The welder rating is 230v at 20amps. The max standard circuit breaker/fuse is designated at 30amps. Their recommendation is to use a 30amp fusible switch between the source and the machine. They also designate a minimum 14 gauge conductor size. (which sounds lite to me)

Specifics to my home. The main panel (200 amp service) is located about 75' from the location of the 230v outlet to run the welder.

My primary question relates to configuring the circuit to use a fusible switch per their suggestion. Do I put a 30amp breaker in the main panel, then run wire to a 30 amp fusible switch located near the welder and then make the connection to the outlet from there.

If that isn't the correct configuration I would appreciate it if you could tell me what is the right way to do it.

Also, I would like to know what gauge wire I should use to carry the 20 amp load over 75' to the welder.

Thanks in advance for your help!

Follow-Up Postings:

RE: Fusible Switch Circuit

The 30 amp breaker is the "fusible switch", no additional required. Article 630 in the NEC permits electric welders to be on circuits with apparently undersized wire (tables in the Article show the sizes) in cases where the duty cycle is below 100%. Your welder might be only 20%. Some of the imports are only 6%. 20% means what one can weld 2 minutes out of very 10 and the welder is permitted to cool for the other 8 minutes. The conductors also cool during that time. I would use #12 for the application. #10 would be better but not necessary.

RE: Fusible Switch Circuit

"Article 630 in the NEC permits electric welders to be on circuits with apparently undersized wire"

Welding equipment, induction motors, and hermetic compressors are have there own code sections.

The wires are not undersized, but based on the characteristics of the equipment.

This equipment contains built in thermal overload protection, so all the breaker is doing is protecting the feeder against short circuits.

The low duty cycle of many welders allows plenty of time for the wires to cool off.

General purpose circuits (15 and 20 amp, 120 V) feeding multiple loads and used many times in every installation are designed with extra margin (#14 wire at 15 amps, #12 at 20 amps) to ensure safety.

RE: Fusible Switch Circuit

Hey Guys. Sounds like I now know what I need to know. Thanks for the help!

 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Electrical Wiring Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here