×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Fractional HP motor & a code question

Fractional HP motor & a code question

Fractional HP motor & a code question

(OP)
I have a 1/20 HP motor on a reducer, 115V.  I want to plug this into the wall.  The motor doesn't include any sort of thermal protection / OL protection.  For 1/20 HP, am I required to provide additional protection aside from the 15A branch circuit protection i.e. circuit breaker?  

I keep getting caught in the loop created by NEC 2008 430.42(C), 430.32, and 430.53.  A code wizard I am not.. but I can't help but think about a simple box fan.  These don't have thermals that I'm aware of.   

RE: Fractional HP motor & a code question

(OP)
It's actually a dual voltage PSC motor.. .I don't think it makes a difference, but I figured I'd better add that in there.  

RE: Fractional HP motor & a code question

Actually, all the cheap,little 115 volt fans I've examined (not many) have had thermal fuses in the windings.

RE: Fractional HP motor & a code question

Most likely it has a "Klixon" thermal switch built-in somewhere. It may or may not have an external reset, some are automatic when it cools, but it would say somewhere that it is "Thermally Protected" or has "Integral Protection", something like that.

http://www.sensata.com/support/klixon-motor.htm

But beware! Dayton (a common brand sold by Grainger) for some reason apparently sells a PSC gearmotor that has NO thermal protection built in, which means you would have to supply it externally in the form of an OL relay. No idea why they would do that, cheap I guess.
http://www.electricmotorwarehouse.com/Dayton/6Z073.htm
If you are going to control it manually with a switch, but a Manual Motor Starter what has a 1 pole heater element, sized for the FLC of that motor (looks like .62A from that Dayton sheet).


(Note: image is from eBay, will eventually disappear)

Box fans and the like often use "impedance protected" motors, a euphemism for it being a shaded pole motor that can be held at locked rotor and not overload. As a "fail safe" issue, they typically have a small wire buried somewhere in the design that will open long before anything else catches fire. They will not identify it as a fuse however, because that would imply it can be replaced, and it cannot.

 


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Fractional HP motor & a code question

(OP)
Thanks for the feedback guys; I think a thermal is an option we can ask for from the manufacturer (cheaper that way).  Waiting for feedback from them now.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources