Kettling boiler

Clive Arthur expressed precisely :

Yes.

A pump swap is usually fairly straight forward, just a couple of large unions to undo and the supply cable. Hopefully it will have a valve either side, to avoid the need to draining down and nothing has seized up.

Before committing to swapping the pump, make sure it is the pump. On the end of the motor is a removable sealing cap, which gives access to the end of the slotted end of the motor shaft. Next time it fails to start, try turning the shaft with a screw driver. If it then runs, the pump does need to be replaced. You could maybe do a practice run, with the system turned off, so you are more confident of what to do..

most likely pump sticking. Cleaning out the central bearing often works. Undo the big central screwhead on the pump, turn the rotor until it's relatively free & put the screwhead back. Check you've got a filter on the system to prevent recurrence.

NT

I unscrewed the cap and water poured out, so I screwed in straight back in.

I guess that's pretty definitive, time for a new pump.

In fact, the pump is inside the boiler housing and it looks like I just need to replace the 'pump head'. There's a YouTube video and it looks easy, unfortunately I'll have to drain the system, there are no isolating valves.

Thanks

Clive Arthur submitted this idea :

Some water will escape, that is quite normal. The thing is to check if the shaft is moving when you are complaining of the kettling problem.

water always comes out, it's a water lubricated bearing. Try again.

NT

It may be the "start" capacitor starting to fail

I finally got a round tuit, and fitted a second hand pump head from eBay. It was simple, a ten minute job after the hour draining the system and before the hour refilling and bleeding. I expect I'll be bleeding small amounts for a while. Yes I did add corrosion inhibitor.

It seems to work fine. If it fails again I'll buy a new pump head.

Thanks for the replies.

Cheers