On Mon, 04 Nov 2019 17:45:19 +0000, Roger Hayter wrote:

wrote:

Joking aside, this sounds like a blocked or scaled up DHW FPHE.

S.
Or possibly a flow switch? Should be easy to check whether the boiler
responds to the call for hot water, most simply with the CH off.

Sounds reasonable.
Running hot for 30 seconds when the CH is on sounds like residual heat in
the heat exchanger and the boiler not firing at all when HW is called for.

We are assuming that HW is actually turned on at the boiler. :-)
There are usually separate controls for CH and HW flow temperature, and
often separate controls to enable CH and HW on the boiler; an alternative
explanation could be that the boiler is accidentally configured not to
supply hot water, only cold.

Always double check things like this first.
On the lines of "Is it plugged in with the switch turned on? Can you see
any lights?" when dealing with computers.


Cheers



Dave R


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