strange boiler problem - no heating when h/w and heating

[steved101]

a work colleague of mine has this problem, and his local plumber has been out and can't figure out the problem!


this is all the info he has given me: so i am thinking it could be a handful of things, without knowing more about the external controls!

i have worked out it is not a combi, as you never have h/w and heating together with a combi anyway!


Gloworm boiler

heating OK when on its own
h/w ok when on its own

but when on both together: no htg!! just h/w

what could this problem be please?

 

[samparker]

sounds like it could be a diverter valve problem if you have one (the 3 port type-mid position). IF you have one, then possibly when it is supposed to be in mid-position it is stalling and not staying there, maybe a faulty microswitch in the actuator (powerhead). very strange though as you say you do get heating on its own. so the motor is working fine.