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[referteacher]

The chillers are single pass evaporators and in series. How can ch-1 have a higher RLA then ch-2 with all things being equal.?

Chiller # 1 runs at a higher evaporator temperature than chiller # 2.

Higher temperature evaporator = higher density refrigerant gas = higher load on compressor = higher full load amps.

Kinda-sorta like when your air conditioner on your house draws more amps when your house is hot than when it's cool.

If'n you could get the origional design specifications for that installation, I'll bet you'll find that's the way it was origionally spec'd.

[Doesn'tPhaseMe]

Trane does the same thing with their duplex chillers. The up stream compressor has a slightly higher kw/amp rating than the down stream even though both are circuits are completely identical. Just like what was said previously the upstream has to take on a little more load than the down stream so therefore a slightly higher rating. But why not make the downstream the same rating if it can do the same work? Kw/ton, if they can derate the downstream compressor and achieve the design specs with less, the manufacturer can use this as a selling point to the potential customer for their plant for operating cost savings.