Combi boiler - Hot water comes lasts about 10 seconds
cf-leeds
The boiler is a Vokera Excell 80 SP.
When the hot tap is opened, the boiler fires up properly and give hot
water for about 5-10 seconds, then the flame shuts off. This happens
with or without the heating running.
Sounds like it could be something simple ?
I would expect different symptoms, if this was a problem with the
diverter valve.
Any pointers appreciated.
Chris
GB
Some combis have an 'instant hot water' feature, which means they have a
small reserve of hot water, so you don't have to wait for the boiler to fire
up to get hot water. Is it possible that you're using this reserve up and
the boiler isn't firing at all?
Skipweasel
@i18g2000yqn.googlegroups.com>, ciri...@googlemail.com says...
> When the hot tap is opened, the boiler fires up properly and give hot
> water for about 5-10 seconds, then the flame shuts off. This happens
> with or without the heating running.
Sounds like it's detecting an overheat on the output. Have you tried
increasing the water flowrate?
--
Skipweasel - never knowingly understood.
Mike P the 1st
<skipw...@googlemail.com> gently dipped his quill in the best Quink
that money could buy:
>In article <f0b4c33d-7498-434a-96aa-5f3f2d0f6f42
>@i18g2000yqn.googlegroups.com>, ciri...@googlemail.com says...
>> When the hot tap is opened, the boiler fires up properly and give hot
>> water for about 5-10 seconds, then the flame shuts off. This happens
>> with or without the heating running.
>
>Sounds like it's detecting an overheat on the output. Have you tried
>increasing the water flowrate?
Same syptoms on mine and it was a water flow sensor not working. Water
was flowing, but sensor said not ... so boiler shut down everytime
after initial fire up.
Mike P the 1st
GB
Oops shd have read the OP more carefully.
--
Murphy's ultimate law is that if something that could go wrong doesn't,
it turns out that it would have been better if it had gone wrong.
Geo
Ybbut he says "This happens with or without the heating running."
Which I take to mean the boiler is fired with the heating "running".
--
Geo
Bolted
As well as other suggestions, it could be the thermostat or the heat
exchanger. I just went through the same loop on a Vokera Linea Plus.
It was the DHW heat exchanger in my case. On the Linea, if you close
off the cold inlet supply valve while hot water is being called for
and when the burner is shutting down, the front panel display switches
from the hot water temp to the temp of the primary circuit. In my
case that was 90C everytime, which is the heat exchanger is fkd fault
code. I have no idea whether the Excell does the same.
cf-leeds
<MikePthe1...@northofwherethecustardstops.com> wrote:
> On Tue, 18 Jan 2011 14:03:12 -0000, Skipweasel
> that money could buy:
>
> >In article <f0b4c33d-7498-434a-96aa-5f3f2d0f6f42
> >> When the hot tap is opened, the boiler fires up properly and give hot
> >> water for about 5-10 seconds, then the flame shuts off. This happens
> >> with or without the heating running.
>
> >Sounds like it's detecting an overheat on the output. Have you tried
> >increasing the water flowrate?
>
> Same syptoms on mine and it was a water flow sensor not working. Water
> was flowing, but sensor said not ... so boiler shut down everytime
> after initial fire up.
>
> Mike P the 1st
Thanks for all the responses. If it is the flow sensor, Is that an
electrical contact ?, i.e. would I just be able to pull off the
connectors from the sensor and check for continuity when the water's
flowing ?
My mate has the full sevrice guide, so I should be able to locate the
sensor and test it.
Chris
fred
<d08b8654-935d-4066...@o4g2000yqd.googlegroups.com>,
cf-leeds <ciri...@googlemail.com> writes
installers' (service) manual is also very descriptive fault finding
sections.
With the case off and the control panel hinged down you will be able to
see a lever based mechanism that should operate when there is flow
through your hot tap(s). You should be able to see if the lever is
operating fully and if giving it a little help to move solves the
problem then you may have a faulty diaphragm in the mechanical part of
the flow sensor. The other end of the lever operates a microswitch
(lower left of case) which gives the boiler electrics the call to heat
on water flow. The actuation point of the switch is adjustable (access
from below, lower left) but it wont help if the diaphragm is split
although it may mask the symptom for a while.
As it takes 5s to cut out, the modulation control (half/full power only
on this model) may be stuffed, follow the faultfinding section on
adjustment of this to set it correctly. Bear in mind that it wont set
correctly if the burners are clagged up so it may be that you need a
full clear out and service but don't open the combustion chamber unless
you feel competent to do so.
It's not uncommon for one with badly clogged burners to shut down due to
poor inlet to outlet airflow (looks like an air switch fault but isn't)
but that would cause heating to be off too.
Also, in general, watch out for loose connections between the loom and
the control board, the loom flexes when you hinge down the control panel
and you can get intermittent connections. The temp setting controls
(potentiometers) on these break if you look at them the wrong way, after
changing them twice I replaced them with fixed resistors set to give 3/4
of max temp at all times.
Spares, inc service kit (diaphragms) are still easy to come by.
HTH
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks