Vaillant turbomax plus 824e

[gors]

I have an intermittent fault on my boiler. When I turn the hot water tap on the boiler fires up as expected but within a few seconds there is a loud noise, the pressure guage shoots up and fluctuates rapidly around 2-2.5 bar and the burner (and yellow light) goes out.
I press the reset button and it restarts and then works fine.
I checked the cap on the automatic air bleed and it was closed tight. When I unscrewed it a short chuff of air came out but unfortunatly the boiler still has the fault.
I have also pumped the accumulator up to .75 bar but to no avail.
Can any one help?

 

[Gasguru]

Sounds like the pumps gone, does the heating work?

 

[gors]

The central heating works fine for most of the time but I do sometimes have to reset it - but that may be because I have used the hot tap when the central heating was on.
Could it be the pump?

 

[gas4you]

Could be the diverter valve stuck in ch position.

Diverter valves on these are a very common fault.

 

[gors]

Yes I have heard the diverter valve is a common fault.
What do you think the loud noise is? It sounds like air or steam going through the pump and rattling the pipes in the boiler.
Could the diverter valve cause this noise?

I have just had to reset it about 15 times just to get some hot water for a shower, it finally reset when I switched the central heating off but that may have been a coincidence. it has worked fine since.

A friend has suggested that the heat exchanger is blocked and will need to be cleaned out or replaced. Could that be it? would a blocked heat exchanger cause these symtoms? Is it a common fault?

has anyone got any first hand experience of these symtoms?

 

[gors]

I just noticed that when the pressure guage rises and fluctuates the temperature also rises vey rapidly into 3 figures and it may be tripping out due to the high temp.
What temperature is the boiler meant to trip out at?

 

[Agile]

Can you explain exactly how you pressurised the EXV and why you chose 0.75 bar?

You may find the FAQ helpful.

The boiler will control itself to a maximum temperature of about 85°C on heating.

Your diverter valve sounds fine.

Tony

 

[gors]

Hi Tony,
Thanks for your reply, The figure of 0.75 bar was in the manual which came with the boiler.
I first let the pressure out of the sysyem at the pressure releif valve and then pumped the accunulator up wth a car footpump to 0.75 bar. I then repressurised the system to 1 bar.

I am now pretty sure the boiler is cutting out due to the high temperature.
Could it be that the pump is not moving it fast enough through the closed loop ?
Cheers
Ceri