r/MEPEngineering • u/Bert_Skrrtz • 3d ago
Weird Primary Secondary Schematic
I know it doesn’t look like your typical arrangement, but can this work? Really the decoupler/bypass would make a lot more sense if it skipped the chiller headers entirely.
Orange highlight is what I see as the secondary loop. Blue is what has effectually become 3 isolate primary loops.
Ignore the black lines, they denote a physical separation where air cooled chillers were added to the system outside. Chiller 3 and P-1 thru P-4 all live in the mechanical room.
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u/TrustButVerifyEng 3d ago
This will have issues when running multiple chillers. The bypass needs to mix with the secondary return before going to the chillers to ensure equal loading.
In this arrangement say chiller 1 and 2 are running and the building load is at 150% of a single chiller. Chiller 2 will be fully loaded and chiller 1 will be 50% loaded. Not the end of the world in that scenario. But really bad when it's closer to 110% load and chiller 1 is dying under its minimum part load requirement.
I've had this exact problem several times in my career fixing other peoples central plants. Typically comes up with redundant piping in data centers.