How are the pumps controlled on a booster system with current sensing relays (CSR)?
The sequencing for a current sequencing panel works by monitoring the amperage draw of each motor on the system. Since current draw is proportional to power, the current draw is a direct measure of the pump load which in turn is proportional to flow. When working with such a system, it is important to note that the lead pump operates independently of the current relays. There are two modes of operation for the lead pump: • Constant run in this case, the lead pump runs continuously independent of any sequence settings. There is an aquastat and solenoid purge system which bleeds hot water should the lead pump run at churn for too long a period of time. • No-flow shutdown in this case, the pump shuts down on temperature as measured by the aquastat and turns back on following a pressure drop (measured by the call or no-flow pressure switch in the panel). Armstrong provides 2 current relays per step of sequencing to give independent ON and OFF set point capability. The sequence for moving u