Pump still running -even when CH/Hot Water off!

[BertieC]

Ok,
Not sure what this is but have noticed that sometimes at night I can hear my pump gently humming in the background. The Ch/HW are both on timed and when I check they are both off and not calling for heat/HW.
In fact even if move both the settings for Ch/HW to off the pump remains on. I have tried waiting to see if it goes off after a while but it does not. In fact the only way of stopping it is to switch the mains power off.
Are these the symptoms of a sticky motorised valve? If so I still cant understand why the pump works if all the controls are off, unless the motorised valves run independent from the control box. In other words would the pump still run if the CH valve was stuck in open irrespective of the fact that the C/h is not calling for heat?
many thanks.

 

[kevindgas]

more likely to be a pump overrun stat problem
post the details of the boiler and one of us will confirm if your boiler has one.

kev

 

[BertieC]

I am afraid that its an old Gloworm Micron 30ff.
No a great boiler by all acounts but it works (sort of).

 

[45yearsagasman]

It may indeed be a overrun stat fault,but from my experience it is more likely to be micro switches in either motorised valve not switching off even though the programmer is set to all off.This may be that the switch is faulty or the valve itself is partly siezed.To aid diagnosis, does the boiler fire up when the programmer has ch and hw off?

 

[BertieC]

No, not that I have noticed but will keep a careful eye and ear out.
Thanks for the replies, both of you.

 

[kevindgas]

haven't looked in one of these for a while but i am sure it has one. have asked GW for a email copy of the manual so i will check and post back for you

kev

 

[kevindgas]

as promised:

the micron is a straight forward boiler with only a temperature limit stat and doesn't not incorporate an overrun
so it is most likely as posted above a valve microswitch issue

kev

PS. if you want the manual email me and i can forward it to you (its the 40 manual but most of it will be the same)

 

[BertieC]

as promised:

the micron is a straight forward boiler with only a temperature limit stat and doesn't not incorporate an overrun
so it is most likely as posted above a valve microswitch issue

kev

PS. if you want the manual email me and i can forward it to you (its the 40 manual but most of it will be the same)

thanks kev,
you have email!