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Low Load Controller™
In order to provide maximum performance system performance and avoid multiple system starts and re-starts Chil-Pak® integrated the Low-Load Controller™. The Chil-Pak® Low Load Controller™ automatically reduces the capacity of the chiller plant to 3% less when required.
In many HVAC applications there is a high probability that in low ambient conditions the total building cooling load may be lower than the plant’s minimum turn down ratio.
The Problem: Total Building Cooling Load < Chiller Plant’s Minimum Turn Down Ratio
This condition may force the chiller unit to shut down and restart numerous times through the low load condition period. The start and stop cycle time period depends on the cooling load quantity, the chilled water loop volume, the time length of the low load period, and the time delays programmed in the internal controls among other factors. The start/stop cycles can be highly undesirable condition since it may dramatically reduce chiller’s electrical motor life.
Many chillers offer a hot gas by-pass design to help reduce turn down ratio to a lower capacity. However, when the building cooling load applied to the chiller is lower than the minimum turn down ratio the chiller automatically shuts down and will automatically restart once the chilled water temperature rises to the chilled water set point plus a hysteresis value.
In many cases, the internal controls in the chiller adjust the cooling capacity based on: the return water temperature, the leaving water temperature, and the leaving water set point. If the chiller is operating with a cooling load that is lower than its minimum turn down ratio, the leaving water temperature will fall below chilled water set point. Most chillers have an internal minimum leaving water temperature limit at which point the chiller automatically shuts down. This low limit value is normally factory set around 2°F lower than the chilled water set point. This low limit value protects the chiller from freezing or from over cooling.
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