Heating and Cooling Season Startup/Shutdown

Several questions arise about when the Central Chilled Water and building Cooling Towers are turned on and off to the buildings, and why switching the HVA/C systems from heating to cooling, and cooling to heating, takes so long to implement.

Currently many of the University buildings are connected to the Central Chilled Water system and some buildings have local building Chillers. To cool the buildings the chilled water is circulated through the cooling coils of the air handling units located in the various buildings, pushing cold air to the occupied space.

Unlike residential units, the majority of these cooling coils (1–10 per air handling unit) are drained as the cooling season ends and are re-filled back with chilled water when the cooling season starts. This is done to protect the coils from freezing during the winter. This is a time consuming process and it takes around 3 – 4 weeks to complete.

Some buildings are designed with process loops and equipment in them that need chilled water year-round. These buildings and areas have been identified and will remain on, they will not be drained in order to provide cooling.

Our goal is to isolate each individual cooling coil, and leave the building pipes full of water to prevent rust and scale from forming on the inside of the piping. However, if the individual coil valves do not hold, we have to fix them immediately, or close the building main valves and drain the whole building.

The normal cooling season is May 15 – October 15. Of course, these are not fixed dates and are influenced by the weather trends and other factors.

In the spring, to ensure an orderly conversion from the heating to cooling season, we start filling the Priority 1 buildings first. In the fall to ensure an orderly conversion from the cooling to heating season, we start draining the Priority 3 buildings first.