De-energize the pump. Remove the screw in the center of the nameplate. The shaft located beneath this has a groove. Place a screwdriver in the groove and move the shaft in the direction of rotation until you have removed the blockage.
Modern self-regulating heating pumps no longer have a screw in the center of the nameplate. However, modern pumps have an anti-block feature. Should a blockage nevertheless occur, the pump head must be removed.
Caution: Hot water may leak out. Please comply with the safety instructions in the installation and operating instructions.
The instructions are also available online on the product pages under the tab called Documentation.