Power out on heating system

[davelondon]

Hi - power has gone on our S plan unvented system - boiler and programmer out.

There is power in the distribution board supplied by a 3 amp box so that's not the problem.

Boiler and all components powered off this board but I can't see any loose connections and it was working fine yesterday morning although the motorised valve for the hot water circuit isn't opening so I have been opening it manually.

The only other thing I have touched is the cylinder thermostat as the screws holding the cover on were loose so took the cover off and checked the connections and there's no power coming into that either.

Any ideas? Boiler is a Valliant Turbomax that was serviced earlier this year and a new fan installed. It's old but one of the good ones.

 

[terryplumb]

What are you using to establish voltages present ? And what exactly are you referring to re distribution board and 3 amp box ??

 

[davelondon]

Found the fault - blown 2 amp fuse on PCB board in boiler. Never had a fuse go in the boiler before in its 15 year life.

 

[dilalio]

Well, the issue now is what caused it to blow and will it occur again!