In article , Ewan MacIntyre
writes
Alastair Rainsbury wrote:
It seems weird that it's only the ho****er upstairs that's not working -
if it was all the hot water, or if everything upstairs (i.e. radiators
included) that didn't work it would make more sense to me.


Alastair,

Can you hear water flowing through the combi when the upstairs taps run?
This is just a basic sanity check to ensure they are actually plumbed in
as you'd expect.

If they are, then I'd suspect that the flow control valve on the boiler
is set too low. You need to check the manual to know precisely, but on
the combi I used to have, it was on the cold inlet to the boiler, and
needed just a flat-bladed screwdriver to adjust.

The commissioning guide to combis usually advises adjusting this valve
so that turning on a tap to maximum will provide very hot water.
However, if the mains pressure changes, this setting can be wrong. I
used to just open the flow valve fully, knowing that if I turned on the
tap too much, the water would actually be cooler than if the tap were on
less.

All of this assumes that your combi is supplied with cold water from the
mains. If it is supplied from a cold tank in the loft, then you might
not have enough head to trigger the flow switch. Also, even with the
mains I suppose the pressure could simply be too upstairs?

Ewan

Do you have a hot tank ?. If you *do* then it will be treated as a
'heating zone', in which case only the kitchen sink may be on the DHW
circuit. If this is the case a 2-way or 3-way valve is stuck preventing
the hot tank primary coil from getting any hot water even though the
rads (on another heating zone) are working fine.
--
Andrew