The difference between the shut off head off the pump, less the static water level, less the discharge pressure of the CSV, determines the differential pressure. When the CSV is in the closed position, the differential pressure determines the flow through the bypass. The higher the differential pressure, the higher the flow through the bypass. The lower the differential pressure, the lower the flow through the bypass. In this way the Cycle Stop Valve automatically adjust its minimum flow to match the pump.
A CSV with a stated 1 GPM by-pass will allow 1 GPM with average differential pressure. With lower differential pressure, this same CSV will have a 1/2 GPM by-pass. With higher differential pressure the same CSV will have a 2 GPM by-pass.
A Cycle Stop Valve with a stated 5 GPM by-pass will adjust itself from 2.2 GPM to 8 GPM respectively. This insures that pumps with higher differential pressures, that require more minimum flow, will receive such. It also insures that pumps with lower differential pressure, that do not require as much cooling flow, will not cycle at lower flow rates. The non-clogging by-pass of the Cycle Stop Valve insures that there is always sufficient flow to properly cool the pump and motor, as long as the differential pressure is adequate.
The minimum differential pressure required for the CSV to function properly is about 20 PSI. The maximum differential pressure that the CSV can withstand is about 125 PSI. However, there are ways to handle differential pressure much higher than 125 PSI. This usually requires multiple CSV's in series to stair step the pressure down. With three CSV's in series, as much as 375 PSI differential pressure can be stepped down, with no more than 125 PSI difference across any of the CSV's. Some CSV's can handle more than 125 PSI differential pressure. Call the factory for recommendations. Flow charts for varying differential pressure are available.