Disconnecting Means

[fifty60]

I know that the NEC requires a line of site disconnect for motors. I have a machine (not technically an "industrial machine") that the customer is requesting a chord/plug be fitted to the machine. They have spec'd out NEMA 15-50 plugs for the machine. Will this type of plug be suitable if there is no other line of site disconnect available for the machine?

Will they have to get a disconnect rated plug and receptacle?

The machines are normally wired directly to a disconnect. It is rare that we have customers request a plug. The machine has 4HP worth of motors, and will need a 50A receptacle.

Thanks,

 

[iwire]

Make sure you choose the right plug.

430.109(F) Cord-and-Plug-Connected Motors. For a cord-and-plug-connected motor, a horsepower-rated attachment plug and receptacle having ratings no less than the motor ratings shall be permitted to serve as the disconnecting means. A horsepower-rated attachment plug and receptacle shall not be required for a cord-and-plug-connected appliance in ac-cordance with 422.33, a room air conditioner in accordance with 440.63, or a portable motor rated 1?3 hp or less.

 

[fifty60]

So I can use a NEMA rated plug that is rated for 7.5HP as the disconnect means for a machine that has 4HP worth of motors? That is how I read 430.109.

 

[fifty60]

To be suitable as the line of sight motor disconnect do the plug and receptacle have to be listed as a "suitable motor disconnect", or do the HP ratings make them suitable as a motor disconnect?

 

[iwire]

Honestly I am not sure how to answer your questions.

To be suitable as the line of sight motor disconnect do the plug and receptacle have to be listed as a "suitable motor disconnect", or do the HP ratings make them suitable as a motor disconnect?

I read it as HP ratings are sufficient.

So I can use a NEMA rated plug that is rated for 7.5HP as the disconnect means for a machine that has 4HP worth of motors? That is how I read 430.109.

I do not know, it seems you are plugging in a machine not a motor. But I am not sure that makes a difference anyway.

Hopefully someone will jump in with some insight.

 

[petersonra]

the language seems ambiguous.

having said that, it is a common practice to hook up multi-motor machines cord and plug and perfectly safe.

 

[petersonra]

one might argue that the machine is actually an appliance and thus does not require HP ratings at all.

a washing machine is an appliance.

 

[iwire]

having said that, it is a common practice to hook up multi-motor machines cord and plug and perfectly safe.

Well yeah for sure.

But what type and rating should the plug and receptacle be? There are a lot of choices.

 

[fifty60]

We would fall under Lab Equipment, not appliance. Thanks for all of the help everyone. We can use the NEMA rated plug or IEC rated plug that has HP ratings higher than the total horsepower of the Equipment.

Do the sufficiently HP rated plug count as a line of sight disconnect? I know looking at some hubbel pin and sleeve devices ( http://www.hubbell-wiring.com/press/catalog/E.pdf ) you can get a simple plug and receptacle for much less money than their "unfused circuit locks with mechanical interlocks".

I am trying to figure out when I would need to get the much more expensive unfused circuit lock with mechanical interlock instead of just an IEC receptacle.