On 18 Sep, 13:52, "Roger Mills" wrote:
In an earlier contribution to this discussion,

iain_b wrote:
Thanks Roger,

Further investigation shows that I've got the S plan system - I think.
Also turning the heating to 'on' won't start theboilerand if the
boileris on with the hot water control, turning the heating to 'on'
will switch off theboileraltogether, I'm confused.

Thanks,

Iain.

You ain't the only one!

Correctly functioning S-Plan systems will run theboilerwhenever either or
both HW and CH are calling for heat, and turning on one won't stop the
other!

Has any work been done on the system recently - particularly replacing one
of the motorised valves (or just its actuator)? I can't explain the symptoms
unless there's a wiring fault, and even so, you'd have to be quite
'clever'[1] to produce this particular effect.

[1] The secondary switches on the valve actuators are supposed to be wired
in parallel. To get this effect, you'd have to wire them in series *and* use
the NO contact on one and the NC contact on the other!

--
Cheers,
Roger
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Hi Roger,

No work has been done on the system.
I'm now totally confused - both the hot water and heating are in the
'off'' position on the controller, but the boiler is still working -
I'm guessing that the controller's internal circuits are goosed and
hopefully a new controller will fix things. It's a British Gas UP1
controller, any ideas where I can get such a thing - I take it it will
be a Honeywell or similar re-badged.

Thanks,

Iain.