Coldwater HVAC Upgrade 2026

A chilled water plant instead of packaged cooling

Every district with an aging chiller gets offered the same alternative: abandon the plant, put packaged DX or split systems on the roof, and never rebuild a mechanical room again. It is a reasonable answer for some buildings. For a high school with a working glycol loop, distribution already in place and staff who maintain it themselves, it is usually the more expensive answer wearing a smaller first number.

The case for the plant here is capacity turndown. Two 160-ton machines give 320 tons at design, and a school in Ohio sees design conditions for a handful of afternoons a year. Splitting the plant in two means one machine carries the shoulder season by itself while the other sits idle, and rotary screw compressors with variable speed condenser fans hold their efficiency well down the load curve. The packaged alternative spreads that same tonnage across a dozen small compressors, each cycling on its own thermostat, each with its own roof penetration and its own end of life.

The second argument is where the equipment lives. Two chillers at grade and four pumps in one mechanical room means every filter, strainer, gauge and valve a technician touches is in two places. That is a plant a district maintenance staff can actually keep on a schedule, which is the difference between equipment that reaches its service life and equipment that does not.

Refrigerant matters on a purchase with this kind of horizon. The existing machines ran R-134a, which was recovered and turned over to the district; the new ones run R-513A. A district buying a chiller now is buying into a refrigerant supply chain for the next twenty years, and that belongs in the decision alongside tonnage.

Because the plant is the building’s only cooling and the building is a school, the sequencing was built around what already existed: the chillers set in the old chiller locations, the pumps mounted on the existing housekeeping pads with new variable frequency drives between the existing disconnects and the pumps, the 25 percent glycol charge drained into drums, held and reinstalled rather than replaced, and the controls integrated over BACnet and programmed offsite so the plant came up on the district’s existing graphics between one school year and the next.