Chillers - How to Size a Chiller

It should be noted that Opti Temp will size the appropriate chiller for your application and takes no legal responsibility if the customer calculates the specific chiller load, and orders a unit without consultation with Opti Temp. The optimum chiller size needed is based on the amount of heat your application is generating, plus additional power to maintain temperature under varying loads.

Normally the manufacturer of the device you are cooling will supply heat removal information. If information isn't available you can use one of the two calculation methods shown below to correctly size a chiller for your application.

How Much Cooling Capacity Should I Purchase?

Opti Temp chillers use their patented ARCC control (Advanced Refrigeration Capacity Control) circuitry providing for no load to full load capacity control without cycling the compressor.  Most other chiller manufacturers cycle the compressor at less than 50% load, which causes increased wear on the compressor and temperature instability. You are then able to purchase a chiller for more heat removal capacity than the minimal required and thus have future expansion for load increase.

Method A

Watts = [(DT) °F x K] / S
Where

  • DT= the °F difference between incoming and outgoing tap water temperature of your instrument.
    Measure carefully using the same thermometer for both locations.
  • K = Specific heat multiplied by the density of the fluid being circulated.
  • Use 2,326 for water when calculating load in °F
  • Use 1,837 for 50/50 mixture of ethylene glycol and water when calculating load in °F
  • S = the number of seconds to fill a one liter container.

Method B

BTU/Hr=GPM x (DT) °F x 500
Where

  • GPM of process fluid to be circulated
  • DT= the °F difference between incoming and outgoing tap water temperature of your instrument.
    Measure carefully using the same thermometer for both locations.
  • Fluid factor for 100% water=500

Sizing a chiller - additional considerations

Please contact Opti Temp for conditions such as LWT temperatures above or below rating point, 50Hz operation, high altitude, E. Glycol,  P. Glycol use, or specialty use fluids.

Conversions

1kW=3412 BTU/Hr
Tons = (BTU's / hr) / 12,000

Chiller or Heat exchanger sizing calculations

In general, consult the factory when determining the model number for a heat exchanger or chiller. In addition, consult the factory when specifying a chiller with glycol or any fluid other than water.