Franklin Electric SubDrive constant pressure pump system controller.

Franklin Electric's Variable Speed controller for constant pressure water well systems is the brains of the constant pressure system. The Subdrive 75 and Subdrive 150 controller both function the same. The Subdrive 75 controls a 1.5 hp 3 phase motor on a 3/4 hp pump end, and the Subdrive 150 controls a 3 hp 3 phase motor with a 1.5 hp pump end.
CP constant pressure water well system components.

Constant pressure control shows indicator lights for troubleshooting.

SUBDRIVE 75 #020143
$ 785.00

SUBDRIVE 150 #020475
$ 1385.00

A small pressure tank is used in the constant pressure system, which eliminates the pressure cycling of the system. The pressure range is controlled by the special pressure switch that keeps the system performing at the desired pressure. Franklin Electric sets it at 50 psi, but you can adjust the pressure with a provided allen type wrench.

The pictures below show you the controller components and features. You can easily see that this is much more advanced than your standard pump control box. Large heat sinks help keep the controller cool. A micro processor controls sending just the right amount of electricity to the motor to speed up the motor to produce more water, and to slow it down when less water is needed. Frequent starts required by your system demand are not a problem, since the Subdrive controller does a soft start of the motor to prevent shock to the system. The Subdrive operates between 1800 rpm and 4800 rpm.

Pressure control for the SubDrive constant pressure pump system.


Standard 230V Single Phase power is used to power the Subdrive control. The controller converts the single phase power into 3 phase power to send to the 3 phase motor, making possible a variable speed necessary for a constant pressure system.