MCP sizing - MCC
MCP sizing - MCC
(OP)
Recently our MCC vendor has come back to us saying that they need to know if the motors in our plant are High efficiency. It seems that High efficienly motors have higher starting currents, which leads to a different size of MCP as compared to that for a normal eff. motor.
If this is true, does this mean that we have to indicate in our MCC list which motors are high efficiency? This will also mean that till the time we get all the data sheets ( though our specs calls for High efficiency motor, some mech. packages have given standard efficiency motor ) we will not be able to finalise the MCC schedule. Is there any way out of this?
If this is true, does this mean that we have to indicate in our MCC list which motors are high efficiency? This will also mean that till the time we get all the data sheets ( though our specs calls for High efficiency motor, some mech. packages have given standard efficiency motor ) we will not be able to finalise the MCC schedule. Is there any way out of this?





RE: MCP sizing - MCC
By the way, most of this info is alluded to in article 430.52 of the NEC by reading the exceptions to the Magnetic Trip Settings for paragraph 3).
So if you notice that last sentence, it says "...the need has been demonstrated..." which is what your MCC supplier is asking you for. Otherwise, without the engineering information up front, someone will have to install the normal breakers and demonstrate to an inspector that they won't work, then change them. This is an expensive approach. The 1700% is a compromise and even though some are as high as 2000%, the duration is very short so (hopefully) the 1700% will work. I have not heard of it not working anywhere yet.
RE: MCP sizing - MCC
If it were me, I'd tell the MCC vendor that all motors will be high-efficiency. I doubt that you will have any problems if "standard" motors are supplied.
I would also specify high-efficiency for all motors unless there is some compelling reason to not do so.