1-phase 1-horse motor.........#6 conductors?

[edlee]

I did an emergency repair today , a hookup to a replacement compressor motor for a dry sprinkler system in a small mixed-use building. The old circuit was 15a 240v single-phase, 14-gauge copper, and the conduit run was about 25' long. The new motor draws nominally 7.35a @ 230v and the installation instructions called for minimum #6 copper conductors.

This seems offhand kind of crazy because I know it will operate on a much smaller wire. But the installers were concerned that if I used something smaller than #6 it might void the warranty. I talked to the local wiring inspector to see if there is something in the NEC referring specifically to sprinkler systems that I didn't know about and he didn't know of anything.

So we wired it in #6 thhn and put it on a 20a breaker.

Any thoughts about why they spec'd that?

 

[John120/240]

Fire sprinkler pumps are designed to run forever or until the fire is out. Being that it is a dry sprinkler system I don't see the need to oversize the supply conductors. The dry sprinkler compressor is used to charge the sprinkler pipe with compressed air only.
Others more experienced will chime in.

 

[tom baker]

My handy Sq D Motor Data Slide rule:
Min copper wire size 14
TM breaker 15 amp

Its a motor load and the rules are in Art 430. I have not seen any other section that would change this.
I would run 12 AWG as I feel 14 is a bit small to work with

 

[kwired]

Manufacturers of this unit must have stock or other interest in a wire and cable company:happyyes: