Elevators: Use Table Value FLA or Actual Nameplate Value?

[DetroitEE]

I'm trying to determine which value we are supposed to base elevator conductor and OCPD calculations on, per code.

430.6(A)(1) tells us to use the table values and ignore the nameplate values, but then goes on to say "motors built for low speeds (less than 1200 RPM) or high torques may have higher full-load current varying with speed, in which case the nameplate current ratings shall be used".

The FLA values from the elevator companies are usually higher than the book value, so I want to make sure that I'm using the right number here.

Does an elevator fall under this classification as a "motor built for low-speed or high torque"? There was a brief discussion on this issue in this thread where Dennis asks a similar question in post #4, but I don't think there was a ever a straight answer, other than "use the feeder size given by the elevator guys". http://forums.mikeholt.com/showthread.php?t=95175&highlight=430.6%28A%29%281%29

Could this also depend on whether the elevator is hydraulic or traction?

 

[Jraef]

Elevator motors (and their controls) are sized for what would normally be considered somewhat extreme duty cycles, even though we would perceive the duty cycle to be low if we watched one operate for a day. I think it's probably as a "safety factor" because they are moving people. This is why you see higher FLA ratings than "normal" motors; for instance a 5HP elevator duty motor may be the same internally as a 7-1/2HP normal motor, but will have the starting / running amp characteristics accordingly.

I always use the FLA if it is higher than the tables, the tables if it is lower.

 

[DetroitEE]

Thanks for the input Jraef, that's probably a good rule of thumb.

Does anyone know if elevator motors are classified as a "motor built for high speed or low torque?"

 

[steve66]

Does anyone know if elevator motors are classified as a "motor built for high speed or low torque?"

Not sure about that, but I doubt it.

The elevator specs I've seen encourage the use of table 430.52 (including exceptions) to obtain the highest overcurrent protection allowed by code. I assume they do this to help eliminate false tripping, which could leave someone trapped.

I assume for most motors that allows one to size the circuit breaker at 250% of the full load amps. That's a lot higher than the standard breaker sizes my Square D table lists for most motors.

Steve