Central Heating Pump

[Madmas]

How do I test if pump is actually pushing water around system ?.
Boiler engineer said water boiler OK but no water is being returned to it, so boiler keeps shutting down. No hot water or heating.
I have been told that even though i can hear and feel pump working, it may still NOT be pumping water.

[htg engineer]

Sometimes the impeller breaks or comes away from the motor, the easiest way to check is to turn off both valves and remove the pump head - check the impeller and replace pump head if necessary.

If you go to the hassle of doing this - would it not be better to replace the pump head anyway, it may solve all your problems.

[Kenj]

Easiest way to test that pump is functioning is to feel the pipes feeding into it and away from it.
When you turn system on from cold, hot water from the boiler should rapidly heat up the flow pipe to the pump. The heat should then pass through the pump, motorised valve, and to H/W cylinder and/or heating pipes.
If the pump is not working the boiler will soon shut down, although the pump may continue running to dissipate the excessive heat from the boiler ( fanned models). An air lock in the pump can cause these symptoms.
Heat will radiate along the pipes from the boiler with the pump not working, but the flow will be very slow, and the boiler will continually overheat and cut out.