Condenser water is pumped to a cooling tower where it’s sprayed out of the top. Percolating downward across honeycombed fill, against the forced airflow upward caused by the fan, the atomized water droplets are cooled by evaporation. The cool water collects in the basin and is pumped back to the condenser side of the chiller to complete the fluid and thermal cycle.
Water is continuously lost from the tower, by evaporation and wind drift as air currents carry water droplets out of the fill boundaries. Some systems provide a steady flow of makeup water, regardless of conditions. If the flow exceeds the losses, the balance is siphoned off to an area drain. This is a practical solution, but wasteful of the water and of the chemicals used to treat it.
A dependable control loop can reduce waste and also provide protection to the condenser water loop. A float switch interlocked with a solenoid valve opens the valve when the water level drops, to supplement the makeup water in the tower basin. If the water level drops too low, indicating an interruption in the water supply or a breach in the basin, an alarm calls attention to this critical problem. That is, if the condenser fluid flow is severely diminished, the operation of the chiller can be compromised and result in much more severe problems.
This is an instance where controls not only help to reduce operational costs, including the water and waste-disposal bills but also help to protect the system from a potentially catastrophic failure.
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Excerpt from Energy Conservation Projects.