Combi boiler will not come on.

[glenn.young]

The boiler is an Ariston EuroCombi SX 20 MFFICE the problem is when we switch the Domestic hot water on in the morning, the water does not get hot, on checking the boiler is not coming on when the hot water tap is turned on. On checking the heating water pressure it dropped below 1 to 2 bar on the water pressure dial. So more water added and the boiler then worked. However, the following morning same thing, the water pressure had dropped again. This time I refilled and put a bowl on the saftey pressure valve. The following morning the bowl had water in and the water pressure had dropped again. However when you leave heating on there is no problem in the morning, only when the heating is off.
Could this be a fault with the safety pressure release, or could the heat exchangers be blocked ( beacuse if I put the heating to full on with water and heating the boiler also nocks off could be flow related ?)
Could it also be the expansion cylinder need to be repressurized >?

Thanks Glenn

 

[ChrisR]

Could this be a fault with the safety pressure release> yes, once leaked they stay leaky.

Could it also be the expansion cylinder need to be repressurized >? more than likely.

the boiler is not coming on when the hot water tap is turned on> diveeter valve or diaphragm trouble . No real reason for it to be connected with system pressure

 

[glenn.young]

Thanks Chris R
So I should replace the safety pressure release valve
also repressure the expansion. Do you use normal air and to what pressure for this boiler.
So you do not think the heat exhchanger is blocked ?

Thanks Glenn

Could this be a fault with the safety pressure release> yes, once leaked they stay leaky.

Could it also be the expansion cylinder need to be repressurized >? more than likely.

the boiler is not coming on when the hot water tap is turned on> diveeter valve or diaphragm trouble . No real reason for it to be connected with system pressure