Conductor sizing for a single motor that is NOT stated to be continuous duty - 125% multiplier still necessary? PPI Exam 1 Question 35

[akyip]

Hey guys,

Quick question about conductor sizing for a single motor that is NOT stated to be continuous duty - is the 125% multiplier still necessary?

PPI Exam 1 Question 35 has a single 3-phase motor that is NOT stated to be continuous duty. I still used the full-load current from the Motor Tables (430.250), but since this was not stated to be a continuous-duty motor, I did not multiply the table FLC by 1.25. Apparently I got this question wrong.

But NEC 430.22 specifically has the 125% multiplier for a single motor used in a continuous-duty application. It doesn't mention anything about a non-continuous-duty motor...

So if a single motor is NOT stated to be continuous-duty, should I still just assume it is for continuous-duty and use the 125% multiplier regardless (for conductor sizing)?

Thanks for any input on this!

 

[Byk]

I think you are misreading the code, it says " a sing le motor used in a continuous duty application". If you go back to Article 100, a continuous load is defined as one where the maximum current is expected to continue for three hours or more. There is no mention of a specific time period with continuous duty. It is also defined in  as operation at a substantially constant load for an indefinitely long period of time. 

My rule of thumb is to always go for 125% unless specified otherwise.

You will need to know the duty application aka classification of service (look at the name plate of the motor) in order to know percentage to use (table 420.22(E)).