Maxin Vokera 28a combi boiler, no hot water, only heating?

I have a Vokera maxin 28a combi boiler that is about 9 years old. I am not getting any hot water when the hot taps are turned on,the temperature fluctuates between luke warm and cool.

I checked out the gauges and noticed that the pressure gauge had dropped into the red, so I turned the screws at the flexi hose to bring the pressure back up, but the gauge gradually drops back down again.

Does any one know what the problem could be ?

Any help or advice would be greatly appreciated.

FUMI, May 2007

Temperature cycling in Vokera boilers of this vintage is a classic fault caused by a lack of a proper service by a Vokera savy Bod who knows the quirks. Google 'Vokera flue venturi temperature cycling'. If your problem matches the google results then the heat exchanger, fan and especially flue venturi need a clean. Does the boiler pressure go right up when the central heating is on?, maybe you are loosing water through the overpressure valve when the pressure is high, or it could be leaking a little, pressure fluctuations mean your expansion vessel needs recharging (google 'combi expansion vessel'). Do you need to give tiny top ups regularly, or prolonged long top ups?, tiny top ups and flat expansion vessels go together.

Best thing would be to get it serviced, though you could recharge the expansion vessel yourself. Corgi men would frown on your opening the sealed combustion chamber and removing the hood to clean the fan, heat exchanger and venturi, if you somehow got the re-assembly wrong it is conceivable that you could get combustion products leaking into your living space. However it is not a difficult task mechanically, if you believe you are a 'competent person'. You can download the manual from the Vokera.co.uk web site.

IMO the least hastle would probably involve phoning Vokera and get a local recommended company to do a proper service, failing that get someone else, who you are sure knows the make and model well, to do it. Should cost around 150 quid. They should also do a few standard safety checks.

c, May 2007

T.h.s

Thank you very much for your reply.

The flame does go out while the water is running.

Kind Regards.

Fumi.

FUMI, May 2007

As far as the pressure loss is concerned you have a leak. I know that sounds obvious but it could be any where. Check around your radiators and valves and also check outside. There should be a 15mm pipe outside near where the boiler is. This is a pressure relief valve and should only vent when the pressure builds to around 3 bar.
Whichever it is, that needs to be taken care of first.
As for the water problem does the flame go out while you are running the taps or not?
If yes poor circulation, or partially blocked pipework or heat exchanger, or faulty temperature sensor among other things. If no, divertor valve may not be closing off the heating port and may be losing heat to the radiators instead of heating the secondary heat exchanger. You can check this by cooling down the heating and then running the hot tap. If you feel the two large heating pipes (22mm) leaving the boiler and going to the radiators they should not get hot for more than a foot or so away from the boiler while the tap is running.

T.h.s, May 2007