Pump not turning off when hot water on

[dpatel]

Hi -

I have a really odd problem. My pump is not turning off once the boiler has stopped burning (even after a long time) when using hot water.

I have a conventional boiler with a pump. Three way motorised valve.

It started after I drained the system to fix a leaky pipe.

I have changed the three way valve (well, the head for it) as I suspected the microswitch in there.

I am getting nice hot water. I have re-drained the system more than once and purged air from everywhere including the pump.

What tells the pump to turn off normally but isn't do so now?

I haven't tried it this since the last drain down/refill but last time the pump would turn off when the central heating was used once the rads all warmed up. So, it seems the pump is only running constantly when hot water only is on (well, at least last time I drained it down that was the case).

 

[45yearsagasman]

I'm sure others get fed up with asking this, but WHAT BOILER DO YOU HAVE!!
Mr Patel?

 

[dpatel]

Oops, sorry. Potterton Profile 60e.

 

[dpatel]

One other thing to mention, once the hot water timer turns off the pump does turn off after ~5min overrun.

But I am sure before I drained it the first time, the pump would turn off once the hot water was up to temperature.