Since fitting the new boiler and controls, her fuel bills have gone now an incredible 48%! Replace the junction box cover and turn the power on at the circuit if your new water heater does not have power, turn the circuit off and check the connections. Source: energysavingtrust.org.uk saving calculated when replacing g rated with a rated boiler in a semi-detached house. Replaced burner assembly on water heater. Fox plumbing.