geoff wrote:
It sounds to me that the fan is short circuit
i.e. knacked
The fuse is telling you that you have a problem (looks like the fan).
Until you solve the problem, you'll keep on blowing fuses
The fuse is a 4A fast blow
look at my site www.cetltd.com

Geoff, even with the fan unit unplugged the system blows the fuse in the
isolation switch?, with the thermostat set to OFF I switch the isolator ON
and a fter a few seconds the boiler ON light illuminates and the fuse blows.
--
Darren