Calculate kW/ton and Coefficient of Performance for Water Cooled Chillers (uses deg F temperature TLs)

Applicable Systems

  • Primary: CHLR

Objective/Method/Outcome

  • Objective: Calculate kW/ton and Coefficient of Performance for Water Cooled Chillers [uses deg F temperature TLs]
  • Method: Uses the temperature difference (entering and leaving temperatures in deg F), flow, and chiller kW to calculate the tonnage, coefficient of performance (COP), and kW/ton. The analysis is performed only when the chiller power is above a user-adjustable threshold (default is 2 kW). The results are stored in CTLs, and the rule does not trigger any insights. {CHLR}
  • Outcome: CTL / No insight

Logic

The logic flow starts by normalizing all the inputs to hourly intervals. When chiller power is above threshold:

  • BTU/hr = (GPM*Delta T*499.8)
  • Tonnage = (BTU/hr)/12000
  • EER = 12/(kW/ton)
  • COP = EER/3.412

(Source: ASHRAE Handbook, Guide to Energy Management (Sixth Edition))

Calculate kW/ton and Coefficient of Performance for Water Cooled Chillers [uses deg F temperature TLs]

Description / Method

Uses the temperature difference (entering and leaving temperatures in deg F), flow, and chiller kW to calculate the tonnage, coefficient of performance (COP), and kW/ton. The analysis is performed only when the chiller power is above a user-adjustable threshold (default is 2 kW). The results are stored in CTLs, and the rule does not trigger any insights. {CHLR}

Rule Template Type

  • Insight Type: Fault Detection
  • Trigger Type: Low

Default Priority

Medium

TL Inputs

InputsUnitsTagsDescription
Entering (Return) Water TemperaturedegFwater, temp, inletTemperature of water entering chiller
Leaving (Supply) Water TemperaturedegFwater, temp, outletTemperature of water leaving chiller
Chiller kWkWchiller, powerchiller power consumption
FlowUS GPMwater, flowoutdoor air temperature

Constants

InputsUnitsDefault ValueDescription
Fluid Factor (water)(BTU/hr) / ( US GPM)499.8conversion from Gallons deg F/ minute to BTU/hr
Chiller kW ThrehsoldkW2.0Threshold for Chiller power consumption to indicate ON

Output Calculated Trend Logs

Output CTLUnitsFrequencyDescription
Chiller_kW_per_TonkW/tonhourlycalculated efficiency
Chiller_Energy_Efficiency_RatioEERhourlycalculated energy efficiency ratio
Chiller_Coefficient_of_PerformanceCOPhourlycoefficient of performance