Chillers and Cooling Towers with Water Loop Heat Pumps

Caution: This article describes a work-around for modeling this system which is not fully supported by Ekotrope yet. This work-around might not provide an accurate analysis for ENERGY STAR Multifamily New Construction in Ekotrope version 4.0.0 or later, but we believe it to be accurate for all other analyses in Ekotrope. Buildings permitted after January 1, 2022 should be using at least version 4.0.0. Please email support@ekotrope.com if you need to model this type of system for ENERGY STAR Multifamily programs. We will not be able to support it immediately but knowing that you need support for this system will help us prioritize its development.

To model a Chiller or Cooling tower in Ekotrope, add a new custom mechanical equipment type and check the box for cooling. If the heat is removed from the dwelling unit with a heat pump, use the spreadsheet attached to this article to calculate the equivalent SEER value of the Chiller or Cooling tower.

If heat is removed from the dwelling unit to a Shared Chiller or Cooling Tower using Water Loop Heat Pumps, you can follow our method to calculate an approximate equivalent SEER, SEEReq, value for the full system. In this case, only a single system must be modeled. The total system cooling capacity is the capacity of the chiller. The SEEReq is calculated with the following equation:

• Capchiller: Chiller system output in Btu/hour.
• COPwlhp represents the seasonal performance of the Water Loop Heat Pump
• Pchiller is the chiller system power in Watts
• auxch: Total of the pumping and fan power serving the chiller in Watts.
• auxdw: Total of the in-unit cooling equipment power serving the Dwelling Unit in Watts (i.e. blower fan).
• Ndw: Number of Dwelling Units served by the shared system.