Chiller efficiency drops rapidly below 50% load. Efficiency loss is roughly 0.1kW/ton worse for each 6% capacity reduction, for operation below 50% load (water-cooled chiller).

For air-cooled chillers, the efficiency may not drop much, due to the reduced ambient temperature beneficial effect.

Load for the chiller will be from control valves that don't close, pumping, and heat absorbed into the distribution piping.

if air handler winter pre-heat is set to 55 degrees F (sequenced with mixing dampers), simultaneous heating and cooling can exist between the preheat coil and cooling coil if they are each set to the same 55 degrees F. This loss can be estimated at 5% of the preheat coll load.

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