Sizing a motor feed when nameplate HP will never be achieved
Sizing a motor feed when nameplate HP will never be achieved
(OP)
Ok, this answer may be right in front of me but your input will be greatly appreciated!!!
When sizing a Motor Feed you size based on FLA of the nameplate...
What if you have an Electrically Commutated motor that has a nameplate rating 4 times of what the motor will be operating at? I know RLA and FLA are two different values. The motor will never be able to operate at its full potential due to software programming and machine design. It is a fan application so there is not a lot of torque required at startup.
My question: Is there any part of the code that will allow me to size the feed based on machine design HP/FLA instead of the motor nameplate?
When sizing a Motor Feed you size based on FLA of the nameplate...
What if you have an Electrically Commutated motor that has a nameplate rating 4 times of what the motor will be operating at? I know RLA and FLA are two different values. The motor will never be able to operate at its full potential due to software programming and machine design. It is a fan application so there is not a lot of torque required at startup.
My question: Is there any part of the code that will allow me to size the feed based on machine design HP/FLA instead of the motor nameplate?






RE: Sizing a motor feed when nameplate HP will never be achieved
No, there are no special rules allowing sizing conductors for branch circuit feeders to motors UNDER the FLA of the motor. In fact, you are not really supposed to use the FLA, you are supposed to use the FLA CHARTS in the NEC that are HP based. The FLA charts in there are typically overly conservative, but the rules are the rules. The only time you use the FLA is if it is HIGHER than what the charts say.
You may know that is will "never" exceed a certain amp rating, but once it is no longer in your control, will the next person? That's why the rules are what they are, they are covering contingencies.
"Will work for (the memory of) salami"
RE: Sizing a motor feed when nameplate HP will never be achieved
Bill
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"Why not the best?"
Jimmy Carter
RE: Sizing a motor feed when nameplate HP will never be achieved
Fair enough, I could not agree more.
Thank you both!