blockCapacities

Information

This subsequence is not directly specified in Guideline36 as it provides a side calculation pertaining to generalization of the staging sequences for any number of chillers and stages provided by the user.

Based on:

• the current chiller stage u index
• the next available higher chiller stage uUp index
• the next available lower chiller stage uDown index
• boolean inputs that determine if the current stage is any of the following: the highest uHigh or the lowest uLow available chiller stage

the subsequence selects from the design stage capacity uDesCap and the minimal stage capacity uMinCap vectors the following variables and outputs them:

• the design capacities of the current yDes, first available higher yUpDes and first available lower stage yDowDes
• the minimal capacity of the current yMin and first available higher stage yUpMin

for the purpose of calculating the operative part load ratios (OPLR) up and down, respectively. The OPLR is defined in ASHRAE 36-2021, section 5.20.4.6.

For numerical reasons and to ensure expected behavior in corner cases such as when the plant operates at the highest or the lowest available stage, the sequence implements the following:

• if operating at the lowest available chiller stage, the minimal capacity of that stage is returned as the stage down design capacity.
• if operating at the highest stage, the design and minimal stage up conditionals are set to a value significantly larger than the design capacity of the highest stage. This ensures numerical stability and satisfies the staging down conditionals.

Parameters

Connectors

Revisions

• January 13, 2020, by Milica Grahovac:
  First implementation.