Hello, TL;DR: My DAB water circulation pump only starts spinning if I help it by turning the inner screw (the one connected to the blades, revealed by unscrewing the big brass screw) back and forth a couple of times using a screwdriver. After that it works properly until switched off and then back on. --- Long Version: Yesterday my central heating system wasn't working. The burner and heater were working but the radiators did not hear up. After inspecting the installations, I found out my DAB water circulation pump which pumps the hot water to my radiators wasn't spinning. I unscrewed the big brass screw to check if it was jammed. Using a screwdriver I turned the inner screw connected to the blade and it didn't feel jammed or stuck. So I tried to spin it back and forth a couple of times and it started to spin and pump the water properly, and didn't stop until I turned it off 6 hours later However, the issue was not resolved. I realized today that I have to repeat the whole process every time I need to switch on the heating. It doesn't spin by itself unless I give it a couple manual spins using a screwdriver (i tested it a multiple of times by switching it on and off). I hope someone can shed some light on what the issue could be, and if there is any DIY solution to getting it fixed.
You might get away with a new capacitor for the pump. If it gets hot and / or buzzes when it should be on but is not spinning this can (but doesn't always) signify that the motor start / run capacitor is faulty. They are usually around 8 microfarads, but rated for 400 (+) volts AC. If you know what you are doing, and can test to ensure all power is off, you might try changing it as a low cost diagnosis. Make sure the power to the whole house is off and that a new capacitor will physically fit.
Thank you all for replying. I asked a friend of mine who happens to be a plumber, and he believes it could be a faulty capacitor as well. I will give it a shot and will definitely follow all safety precautions. I'll keep you posted.