Circuit breaker for Chiller

[AusLee]

Hello,

The catalog of a chiller says: "Nominal Current 600A". It is protected by an 800A C.B.

But then a few liens below, they say: Maximum Current (under Maximum Input Power???) 814 A. Must i change the C.B to 1000A? I think this value can mean a sustained current, what do you think?

Another question please: is the Rated Load Amps (RLA) = Nominal Current? and is the Locked Rotor Amps (LRA) the starting current and how much time does it take to go down to RLA?

 

[jraef]

Chillers can experience a lot of rapid load surging not normally seen in other motor applications. What you have discovered is that chiller manufacturers don't necessarilly do things the way other motor manufacturers do, they tend to go off of their own standards and nomenclature. So yes, the "Nominal" current is the number to use for protective devices and RLA is what you use as you would use FLA. The "Maximum" is a kind of momentary surge rating, similar in concept to a Service Factor. Do not change to a 1000A CB. Use the suggested 800A CB (since it can probably only be loaded to 640A anyway) and if you have nuisance tripping, consider using one with adjustable trip delays.

JRaef.com
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