Does the burner light intermittently on both ch and hw this is prob the case and would indicate an air pressure problem. Check Venturis in fan. Check tubes from Venturi to pressure switch are clear. If both are ok then probably air pressure switch.
Danny
Danny, November 2010
the f30 doesn't have a plate heat exchanger!!
dunk sun, October 2010
prob your plate heat exchanger common fault you can try to descale it or buy new expect to pay around £70 plus labour for plumber
