On Wed, 09 Oct 2019 20:00:01 +0100, T i m wrote:

Hi all,

A while ago some might remember me mentioning here that an elderly
neighbour we keep an eye on was finding heating on when she only
wanted hot water. I believe the diagnosis was the rubber ball in the
motorised valve was allowing water past into the CH cct when in the HW
position and I bought a new valve ready.

She was happy to just use immersion for HW so I thought we'd wait till
it was a little bit cooler in the loft and in general before doing the
job.

She mentioned to the Mrs earlier that it was starting to get a bit
cooler and so I just popped over to swap her back to the gas boiler
and re-set the timer to get things flowing again and whilst it looks
and sounds like it's trying to spark up, it's not managing to?

We have the water pump running (checked via the spindle cover), the
boiler fan, the igniter bit it looks like it might fire up a pilot
flame failure detector main burner but isn't getting the pilot, if
that's actually what happens. If it should light the main burner
directly from the igniter it's not doing that either. [1]

I can't smell any gas on the outside but I can feel reasonable
airflow.

Turn the main boiler knob to off, leave it a few seconds, turn it back
on again, and you hear the fan come on, then after a few seconds
delay, a fairly loud 'clunk' (gas valve?) and then the igniter starts
going but that's it? She has gas on the hob nearby.

Anyone had / got one and can remember the fire up sequence or can
offer any other thoughts please?

I've swapped her back to the immersion heater for tonight and can have
a closer look in the morning.

Cheers, T i m

[1] If you peer into the boiler though the spy hole and watch
carefully, every 3 or 4 sparks it looks like it is surrounded by a
tiny flame but as if it's blown out before it can build up?


Update:

The slowness to fire up still persists but it may be that's just how
they are. However, whilst it takes a while (10's of seconds) it does
seem to fire up reliably.

A secondary issue was that it didn't seem to come on when in 'Heating'
and that was as determined by some deeper fault finding with the DMM
down to both of the micro switches in the motorised valve being faulty
(O/c, one on the n/c and the other on the n/o when actioned).

I replaced the head earlier and tested it on HW, CH and HW+CH and it
seemed to respond as predicted (watching the valve actuator with the
cover off).

There is the possibility that a pre-existing fault remains and that
was leakage of water past the valve when in HW only, causing the CH to
come on when not called. I need to check for that when the system is
cold and have a new valve top plate that I can change if required.

Cheers, T i m

p.s. Just for the S&G's, I may try to locate replacement micro
switches, replace them on the old head and then see if it behaves as
it should (on the bench ... I can make a suitable stop with some mole
grips on the spindle).