"Gravesy" wrote in message
oups.com...
I am having problems drawing hot water from my Vaillant Turbomax
boiler. Sometimes it will be fine but most of the time it takes an age,
if at all, to get any hot water through.

The diverter valve was replaced at the beginning of the year so I do
not think it is this. The central heating is fine.

The green demand light flashes but the boiler does not fire up. It
makes no difference if the heating is on or off, it is alwyas the same!

Any ideas?


You need to do some fault-finding. I would do some basic experiments first
of all to elicit what the boiler is actually doing.

First thing I would do is check if the boiler actually lights when you turn
a hot water tap on. Although you cannot see the flame with the front panel
on its easy enough to hear it 'whoomph' and you can see hot exhaust issuing
from the flue.

If it lights and stays on, but you get no DHW it would blow up, because the
heat couldn't escape from the primary heating loop UNLESS it was actually
going to your CH. I see you've had a diverter valve changed but you must
eliminate it from your investigation. Also, does the diverter make the usual
changing-over noise when you have the CH running and then turn the DHW on at
a tap? I can hear it do that from my bedroom if its quiet and someone turns
a tap on as the sound transmits via the pipes. If the boiler lights but you
get no hot water, try this experiment when the CH is off and see if hot
water is still in fact getting to the CH pipes and radiators when it
shouldn't be.

If the gas lights momentarily when you open a hot tap up, but then goes off,
or it doesn't light at all, that could indicate all sorts of things. I did
hear that some of the Turbomax units suffered from air pump faults ( I
presume this is the centrifugal pump that sucks air in for combustion, or
maybe they meant the sensor which detects the pump is running via the change
in combustion chamber pressure - there are various interlocks which will not
allow the unit to fire up if the sequence of events doesn't happen right ).

I should try the things I suggest unless someone else magics up an answer,
then get back to the group and say what happened, diagnosis needs lots of
evidence,

Andy.