Boiler burner keeps cutting back to pilot but demand is unsatisfied

[SueMax]

I am trying to trouble-shoot my parents' old system. They have an old Ideal Standard 50E CF boiler. Runs well (we keep thermocouples changed from time to time). Very simple system. Recently the boiler lights (no pilot troubles), then loooong before the demand is satisfied, the boiler cuts back to pilot only. Then, after a sustained period (rads all cool, very cool), the boiler lights again and it does the same thing. The roomstat is never satisfied.

The boiler seems to get very hot (whatever the number the boiler stat is set to). The pump seems to be working (pump is in airing cupboard near cylinder) (although I suspect it needs three more speeds!). Hot water is good (never a problem there) (fully pumped). One rad in bathroom gets hot. Generally the upstairs is FAR hotter than downstairs.

It seems to be a circulation problem to me - boiler thinks it has done its job, since there is hot water there (i.e no cold / cool has arrived due to the circulation issue). Am I on the right track, do you think? The hot water does not seem to be being carried away from the boiler adequately.

We recently did chemical clean (it helped a bit, ie downstairs rads have more capacity to get hot when the boiler is in the mood!).

All ideas welcomed!

Thanks

Sue

[Puddle]

Think you are on the right track with circulation problem,maybe pump on its way out,motorised valve not opening correctly or maybe part blockage causing restriction

Did problem suddenly appear,when you did chemical clean,what was water like ?

[SueMax]

Think you are on the right track with circulation problem,maybe pump on its way out,motorised valve not opening correctly or maybe part blockage causing restriction

Did problem suddenly appear,when you did chemical clean,what was water like ?

Thanks, Puddle, for quick reply.

Nope, chemical clean was an attempt to ease this problem. I think it kinda snuck up on my parents, not sudden. As I said, it's a really simple system (antique programmer - the one with the round knob which has only six options and the blue and red time slot buttons to push around the round time clock). I don't think the motorised valves in the airing cupboard work at all (!), but there is no opportunity to have CH without HW anyway. Also, I fear the programmer works the pump and not the valves. (Think it should work the valves, shouldn't it?).

[SueMax]

BTW - tank stat fitted but does not seem to work! That is presumably where the duff motorised valves come in.

[heliotrope]

BTW - tank stat fitted but does not seem to work! That is presumably where the duff motorised valves come in.

Looks like you answered your own question. Your description of system or faults not very clear.

Seems like it's time to get someone in to sort things out.