) General Motor Applications. For general motor applications,
current ratings shall be determined based on (A)(1) and
(A)(2).
(1) Table Values. Other than for motors built for low speeds
(less than 1200 RPM) or high torques, and for multispeed
motors, the values given in Table 430.247, Table 430.248,
Table 430.249, and Table 430.250 shall be used to determine
the ampacity of conductors or ampere ratings of switches,
branch-circuit short-circuit and ground-fault protection,
instead of the actual current rating marked on the motor
nameplate. Where a motor is marked in amperes, but not
horsepower, the horsepower rating shall be assumed to be that
corresponding to the value given in Table 430.247, Table
430.248, Table 430.249, and Table 430.250, interpolated if
HP and nameplate FLA are two different things. FLA is input current. HP is output power. Tells you nothing about power factor or efficiency so you can't accurately determine FLA from that.If a motor operated appliance lists FLA, you're allowed to use this current and you're not required to get the FLC from the NEC tables right?
So by extension, when a motor or motor appliance only lists HP, then you must use the tables??
You use FLA for overload sizing. FLC for everything else under 430.
But what you are describing sounds more like a 440 application which uses totally different rules from normal motors.
Ignorant Brit strikes again. Two questions this time.
What is the difference between FLA and FLC?
Full load Amps and full load current?
We'd usually use FLC as the abbreviation.
Second question.
By 440 application I assume you mean 440V ? Apart from that not being one of your standard voltages, in what way does it differ from what you consider to be a "normal" motor that requires totally different rules?
Information appreciated. Thank you.FLA and FLC are the same thing. I find FLA more commonly used over here.
“440” application refers to NEC article 440 - Air conditioning and refrigeration equipment.
No. That is incorrect. Commonly done, but commonly incorrect.FLA and FLC are the same thing. I find FLA more commonly used over here. ...
The current is motor-specific, so overload protection needs to be sized for that.If a motor operated appliance lists FLA, you're allowed to use this current and you're not required to get the FLC from the NEC tables right?
So by extension, when a motor or motor appliance only lists HP, then you must use the tables??
There is nothing in the NEC that says that, in fact the language from 430.32 says:No. That is incorrect. Commonly done, but commonly incorrect.
FLA is the marking on the motor nameplate by the motor manufacturer for the motor's Full Load Amps.
FLC (Full Load Current) is a current value from a table in the NEC (430.247 through 250 depending on source) that is assigned to each HP rating. You are REQUIRED by code to use the FLC values from the table, NOT the FLA from the motor, for sizing conductors, switching devices and short circuit protective devices. The reason is that someone may someday change the motor and it may have a different FLA on the nameplate, but if you sized everything via the chart, the numbers they used are conservative enough to make it (relatively) safe to do so.
The ONLY thing that you use FLA for is in selecting running Over Load protection, a.k.a. heaters or settings on adjustable OL relays, VFDs, soft starters etc..
....motor nameplate full-load current rating ..
There is nothing in the NEC that says that, in fact the language from 430.32 says:
...motor nameplate full-load current rating ..
OK, I see what you mean. You're right, it never says FLA vs FLC. It is explicit as to the difference between using the nameplate and using the charts, but it doesn't actually say FLA (or the words) anywhere. I stand corrected, I guess that was something I was taught in order to help avoid that confusion.
But maybe this is why... since you will never see the term FLA anywhere OTHER than on the motor nameplate, that's a good way to keep it straight. In fact NEMA MG 1 gives a definition of FLA as meaning "Full Load Amperes", and requires that "Amps" be shown on the nameplate, but it does NOT provide a definition of "FLC" nor use the word "current" in the nameplate requirements.
Semantics though.
There is nothing in the NEC that says that, in fact the language from 430.32 says:
OK, I see what you mean. You're right, it never says FLA vs FLC. It is explicit as to the difference between using the nameplate and using the charts, but it doesn't actually say FLA (or the words) anywhere. I stand corrected, I guess that was something I was taught in order to help avoid that confusion.
That’s what I was taught. And yes 440 is for HVAC which includes compressors and equipment that includes motors where the sizing rules are a bit different. I might have to actually visit Europe some day to be called an ignorant Brit. Guess dumb southern redneck will have to do. I learned 440 in the Code not on the wall socket. Under that section there is no table...you use name plate.
I’m going to look closer though because at least on the exam for 9 states they use FLC and FLA as you describe them. I know there are some trick answers where using name plate gives you the wrong answer. JC Rodriguez writes the tests for 8 states and he doex it that way. He doesn’t write NC exams but they do it that way.
And I agree with your logic especially because I work for a motor shop. FLA changes a little even when we rewind.
Not 100% sure but I think the table values are based on converting HP to kw then applying a 0.85 power factor and using the ANSI standard utilization voltage so for instance 460 then calculating amos. That should be pretty close to worst case on just about any motor except maybe some strange ones like NEMA curve D.
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"Appliance" is defined in article 100;...
Question is what does exception 3 typically apply to?
Appliance. Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air-conditioning, food mixing, deep frying, and so forth.