How to Maximize the Energy Saving When You Replace an Old Chiller

Replacing an old water chiller for the air conditioning system with a brand new chiller will definitely save energy but how to maximize the energy savings and money savings by this measure? Replacing a chiller is a big investment for the building owner and they need to make sure they get the best return on investment from this measure.

Therefore, a comprehensive review for the chiller system and its controls is recommended to determine what equipment and controls needs to be replaced or upgraded and here comes the role of the energy auditor to review and inspect the chiller system and provide the building owner with quantified recommendations that show the energy saving and the return on investment for each one, which allow the building owner decide on what to replace to achieve the best outcome of this investment.

The energy auditor will review the chiller system as a whole including all its components and controls to advise the building owner on which items should be replaced with the chiller as a one project, which makes it more cost effective and require less time rather than replacing them in a separate projects after the new chiller is installed.

What to consider when you replace an old chiller?

The followings should be considered when replacing an old chiller:

  • New Chiller: the new chiller should be high efficiency type with variable speed such as magnetic bearing turbocor chiller, variable speed screw chiller or variable speed scroll chiller. These types of chillers have high efficiency at part load where the chiller runs most of the time. If the chiller is an air cooled type, we recommend to be equipped with an adiabatic system to improve its efficiency further.
  • Chiller Controls: In most cases when an old chiller is exist, an old controls and an old Building Management System (BMS) is used to control the operation of the chiller system. These controls usually don’t have energy efficiency control strategies that increase the efficiency of the chiller system and therefore, should be replaced or upgraded to include the following strategies:
    • Chilled Water Temperature Setpoint Reset.
    • Condenser Water Temperature Setpoint Reset.
    • Optimum Start/Stop
    • Demand Limiting
  • Chiller System Operation : Most of old chiller systems operation is constant flow and this old design is not efficient. Changing this operation from constant flow to variable flow will save in pump energy consumption. This is usually can be done by installing Variable Frequency Drive (VFD) to the pumps and converting the three-way valves in the system to two-way valves. If the three-way valves can’t be converted to two-way valves, then they should be replaced with two-way valves but in this case, a high capital cost is required which leads to a low return on investment.
  • Chiller Pumps : Chiller pumps should be also inspected and if they are in bad conditions and have low efficiency motors, then they should be replaced with new pumps with high efficiency motors.
  • Chiller Cooling Tower: If the fan of the cooling tower is constant speed in case you have water cooled chiller, it should be modified to variable speed fan and its control strategy in the BMS should be upgraded. If the cooling tower also in bad conditions, it should be replaced or renovated.

For a comprehensive review and energy audit to your chiller and air conditioning systems, please contact AESS.

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