boiler failure

[Vass]

I have had a drained system for about 8 months (Wickes 40) have replaced all copper and radiators Re-wired the room stat (hopefully the right way) Switched on, called for heat and the boiler lit up, banged and clattered, then returned to pilot light only. The pump went very hot, but pipes either side were cold so either this is going the wrong way due to the stat wired wrong, or its seized? (it was new last year) All rads filled with water no problem before I started with the boiler. Is the boiler in need of some form of bleed also? any help appreciated ta

[Mitch]

Are all isolating valves at boiler open? Make sure at least one rad has vales permantnly open to cycle water.

If still no good why not try unscrewing large headed screw on pump to see pump rotates?

[Vass]

yes all trv's open and master rad also open will take a look at the pump, thanks for info

[Mathew Newton]

It sounds like the pump is running dry (hence heating up from friction).

Try removing the cap of the pump (usually a brass screw) to release air - ideally it should start dribbling confirming there's water in there (tighten it back up again afterwards).

If the boiler has an automatic air vent on the top also make sure the dust cap on that is loose.

Mathew

[Ed Sirett]

Sounds like you were a bit to keen to get the boiler fired up. I often start the system with the gas off to give me a chance to know whether all (enough of) the air is out of the critical places before puting the gas on. With experience you can hear/feel the difference between a pump mostly full of air and doing nowt and one that is noisily pushing bubbles around.

For a brand new pump the rear bleed plug must be opened to wet the bearings, but helps little is removing air from the circuit.

Auto air vents are helpful but you need to be careful that they are doing their stuff. They often work nest just after the pump has stopped.

[geoff]

In message , Vass writes

You can't wire it so that it goes the wrong way round - it's AC

Do you have isolating valves on the pump, are they open ?

You might have an air lock,

It might be seized, or the impeller might have broken off the ceramic shaft, or you might have displaced some crud which has got lodged and is stopping the impeller turning. Undo the big chrome screw if you have one, you should see a bit of water dripping out and you should be able to see if the shaft is rotating

[John Rumm]

Once the pump works, turn the gas off to the boiler for a bit, and let it run the pump. That ought to shift any air out of the boiler and into one of the rads.

[Vass]

Thanks to all for your input I have removed the chrome screw from the pump, water drips out (may be from use last year?) inside I can see a brass slotted head, which is not turning when heat is called and the 3 way valve moves to position should this brass bit rotate? can I give it some assistance with a large screwdriver? (isolating valves each side are open) Ta

[Vass]

all done! the pump turned with a little turn from a screwdriver felt a little gritty, then it sprang into life Whole house heating up nicely, with the new master rad taking the longest to heat up (farthest away from boiler)

thanks to all for your input, after a week off, fitting all the new rads and pipes, it was disheartening to have a boiler prob right at the 11th hour Beer now (err ok in a few hours) Cheers again