T i m wrote:
On Tue, 12 Jul 2016 22:04:52 -0000 (UTC), Tim+
wrote:

T i m wrote:
On Tue, 12 Jul 2016 21:30:01 -0000 (UTC), Tim+
wrote:


or failing pump
probably.

It's yer classic Grunfoss 3 speed and sounds like it running ok (and
again, you have a good flow round the system).

Not unknown for impellers to come adrift of the motor shaft or just get
eroded away through corrosion/cavitation. But if pipes are heating up
quickly downstream after firing up then probably okay.

Check.


Okay, I'm out of ideas. ;-)

Yeah, me too, apart from taking some measurements and seeing what I
find ('you can manage what you measure' etc).

My background 'fear' is there is nothing wrong with anything and that
the upper limit stat has just got weak?

Possible but given that it's a safety device probably not wise to assume
it. ;-)

Is there any chance of localised overheating in the boiler due to an
airlock in the top part of the boiler? Without sufficient water to carry
away the heat an air pocket trapped at the top of the boiler could
(theoretically) cause localised overheating.

Of course good design and pipe outlet positioning should eliminate this but
without seeing your boiler I can only speculate.

Tim


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