The circulation pump is water lubricated and cooled and requires the presence of water at all times. These pumps should NOT be operated without water present in the spa. If "dry run", the pump has an internal safety device (thermal cut-off) that will automatically shut down the pump should it overheat.
The Silent Flo 5002 is a two-speed pump. When the heater is activated, the high speed pump will be operational. The low speed pump will be operational at all other times.