I'm trying to help a friend get his hot water working again.
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
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?
Sounds like it's detecting an overheat on the output. Have you tried increasing the water flowrate?
On Tue, 18 Jan 2011 14:03:12 -0000, Skipweasel gently dipped his quill in the best Quink that money could buy:
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
Oops shd have read the OP more carefully.
Ybbut he says "This happens with or without the heating running." Which I take to mean the boiler is fired with the heating "running".
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.
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
In article , cf-leeds writes
I look after one of these and it is very user friendly to work on, the 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
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