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4.2 Chillers/Towers and Enclosures

Location to typically conform to CPS standards for on grade location. If roof mounted, review and obtain permission from CPS. Existing roof mounted air cooled chillers will likely remain roof mounted. Conform to all required codes.

Refer to Volume 3, Chapter 6 for additional requirements. Refer to 6.3.6 for Building Controls.

Roof mounted locations

  • Typically to be replaced if removal is necessary for roof work. Often depends on the age/condition of the unit and the existing platform height.
  • Ensure the platform is of sufficient height to accommodate the greater of new roof insulation thickness plus snow such that removal will not be required for future roof repairs.
  • Platform shall include permanent ladders for access and railing if walkable platform required for proper maintenance.
  • Perform sound calculations to determine extent of attenuation / enclosure (for site / sound issues) required to comply with current code, change in use of adjacent schools spaces/rooms above & below and neighborhood buildings.
  • Units shall be sufficiently away from the edge of the building for safety and visibility issues (minimum 10’-0”). Where 10’-0” or greater cannot be maintained obtain approval from CPS on a project/unit specific basis to utilize safety guard rails. Provide site line study for approval by CPS. Access harness tie down solutions shall not be utilized. Any unit mounted greater than 30” above roof level to be reviewed with CPS for proper access to the unit.

When replacement of water cooled chillers or cooling towers is required, obtain approval from CPS. CPS may choose to change to an air cooled chiller solution where appropriate.

As part of the renovation, associated pumps and unit control valves must be evaluated. It is common to convert to variable primary pumping with VFDs and 2-way modulating valves at air/handling equipment/terminal units at the time of the renovation for code compliance and or energy reduction in lieu of keeping constant volume pumping with 3-way valves.

Where towers are utilized, provide VFDs per cell, an inlet motorized isolation per cell, individual tower bypass line with modulating control valve per cell and basin heater per cell (minimize shoulder season short term cold spell draindowns).

Where existing towers are reused and the associated water cooled chiller is replaced, confirm the new chiller operating parameters are compatible with the tower. The new chiller flow must be within the operating range both min and max of the existing tower cell(s) under all operating conditions.

Where water cooled chillers or other refrigerant based cooling equipment is provided, determine if the room is a refrigeration/machine room per Chicago Building Code. Provide refrigerant detection system and dedicated emergency refrigerant exhaust fan for all code machine rooms. CPS may require detection and emergency fan in non-code machine rooms. Review with CPS during schematic design.

Where ethylene glycol (EG) exists or the system glycol has not been changed in more than 5 yrs, drain and clean the entire system. Change or refill with a 30% propylene glycol (PG) solution. Evaluate existing coils connected for performance impacted and make recommendations to CPS during design. Once approved, reselect coils as required. If the existing fluid in the system is water and any equipment coils connected to the chilled water system are exposed to outside air (AHUs, RTUs, unit ventilators, etc.), drain/clean the entire system and refill with 30% PG.

Eliminate absorption chillers when replacement is required. Utilize electric chillers. Evaluate electrical service/ distribution impact and review with CPS before proceeding with full design.

Refer to Volume 3, Section 6.3.2 for Chiller requirements and design considerations.