Grundfos SQFlex Solar Pump Hydraulic End

The SQF pump range comprises two pump technologies: the helical rotor pump (3 in) for high heads and small flow rates, and the centrifugal pump (3 in and 4 in) for low heads and large flow rates. The modular pump and motor design facilitates installation and service. These are the hydraulic ends Grundfos lists separately on its 2026 renewables price list — the pump end without the MSF 3 motor — for returning a worn SQFlex pump to service on its existing motor.

Helical rotor pumps cannot be separated from the motor as a unit: if the motor or the pump has to be replaced, the pump must be dismantled, following the Grundfos service instructions summarized below. Centrifugal pump ends detach from the motor at the four nuts on the suction interconnector.

Before assembly. Disconnect the electricity supply to the motor. Clean all parts and check them for fractures and wear, replace defective parts, and moisten rubber parts with soapy water before fitting them. When fixing the motor in a vice, tighten only on the 30 mm wide area starting 37 mm from the upper edge of the motor sleeve. Before connecting the pump to the motor, fill the motor with Grundfos motor liquid: stand the motor vertically with an inclination of about 10°, remove the filling plug, inject motor liquid with a filling syringe, move the motor from side to side to let air escape, then refit the filling plug and make sure it is tight.

Helical rotor pump — assembly.

1. Fit the pump rotor to the torsion shaft and tighten to the correct torque, holding the pump rotor with a pipe wrench on the cylindrical part below the rotor.
2. Fit the torsion shaft to the motor shaft and tighten to the correct torque.
3. Fit the pump stator, with the conical stator inlet against the strainer, into the outer sleeve.
4. Fit the flange into the outer sleeve and press it onto the upper part of the stator, fixing the stator in the centre of the sleeve. On 11 SQF-2, turn the flange with the even surface against the stator.
5. Fit the discharge chamber with valve casing complete — grease the thread — and tighten to the correct torque, holding the pump on the weld just above the upper strainer.
6. Moisten the pump rotor with clean water, fit the pump on the motor and tighten to the correct torque.
7. Refit the end cover with socket and cable if it was removed, then the cable guard.

Centrifugal pump — fitting pump to motor.

1. Screw the shaft end onto the motor shaft and push it home. Adjust the height to 88.15 mm ±0.2 mm with the measuring template, tighten the nut to the correct torque and check the height again.
2. Fit the supporting ring and the spline protector.
3. Fit the connecting piece and tighten with a pipe wrench.
4. Fit the pump to the motor with the cable recesses in the suction interconnector and the connecting piece next to each other. Fit the four nuts and tighten diagonally to the correct torque.
5. Refit the end cover with cable if it was removed, then the cable guards.