This normally due to low water pressure, most of the time just by increasing the pressure to 1.2 bar and hitting the reset button the boiler will fire up.
Low water pressure is due to the system losing pressure somewhere, the boiler senses this and shuts down to protect itself. This problem will need to be rectified should it become a regular thing.
It means the system is losing pressure somewhere so
The first check is to make sure there are no leaks on the system,
check around the radiator valves, look for marks on the ceiling, look for any signs of staining.
this takes up the water expansion as the water heats up,
should the expansion vessel fail then the fault code F 75 can show up.
When the boiler is serviced the expansion vessel should always be checked and reset if needed,
for some reason this seems to get missed out of the service.
The vessel is charged with air to 0.75bar when it leaves the factory.
when this happens the vessel will start to fill with water.
If the vessel has water in when the boiler is working,
it will start to discharge the pressure through the safety valve. If this happens then the Fault code F 75 will display
and it has not done this before then you need to call in your local gas safe boiler engineer to check over your boiler and ask them to check the expansion vessel
Both of these fault codes have similar answers when you check the Vaillant Eco-Tec book.
If either of these codes appear and after reseting the boiler you find the boiler does not fire up you need to call in your engineer.If the boiler fail to work then the pump needs to be checked to make sure it is running,
These switches can get clogged up with sludge and do not detect the water pressure rise when the pump runs.
If this is the case then it is advisable to have your system cleaned out and an inhibitor added once the boiler has been repaired.
If you notice any strange noise or anything out of the ordinary with your boiler,
then don’t leave it hoping it will go away, call someone in to check it over.
If you don’t do anything about it you could end up with a big invoice for the repair,
when it eventually stops working, you may even end up having to replace it for a new one. All of these high efficiency boilers of today whatever make,
need to be serviced and looked after.
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Duval Heating 1985 - 2019