Fault B51 – Ideal Evomax 2

Ideal Evomax 2 boiler is showing fault no. B 51? There is usually a very simple solution. B 51 means the boiler can’t operate because the water pressure is too low.

Dealing with low water pressure:

If your heating system does not have an automatic filling device (pressurization unit) then the problem can be solved by opening the filling loop for a few seconds to top up the water pressure. Be sure to keep an eye on the pressure gauge. Pressurizing the system too high can bring a host of problems. The Evomax 2 is capable of working up to 6 bar but your pipework may not be. Most systems work at a pressure of somewhere between 1 and 3.

If your system does have a pressurization unit then this can be overridden by again using the filling loop. However, this may have gone to fault too if it is not topping the system up. In this case, take a look at the pressurization unit as this may be the problem.

If this sorts the problem you still need to determine why the pressure has dropped. It may be something simple e.g. radiators have been bled to remove air in the system. However, there could be a leak somewhere which may not be immediately visible if the pressure has dropped slowly over time.

Water Pressure is fine:

If the water pressure is correct and you’ve tried topping it up and this has not resolved the problem then it could be that the water pressure switch is either not connected properly or it is faulty. In this case, ensure that all the wiring connections from the water pressure switch are connected and properly pushed home. If they are and the problem still persists then it is likely you will need to replace the water pressure switch.

The water pressure switch will look something like this: