Main HE A Electronic Control (PCB) 5121025 is the control centre of this appliance. It controls and monitors every process that occurs via the sensors, switches and thermostats. It also enforces the safety parameters, making sure that the boiler ceases to function if any of the internal readings point to any kind of error or fault. Main HE A Electronic Control (PCB) 5121025is effectively the brain of your boiler; It is programmed to ensure everything is running as it should. Heatingspares247.com is one of the UK's largest independent Boiler Parts & Heating Spares Stockist, We specialise in the supply of Genuine & Original Boiler Manufacturer Spare Parts for all leading manufacturers. Services available are trade counter pick up, Next working day, next working day AM and Saturday delivery. We also operate same day express delivery service. Our Opening timers are Monday to Saturday, 8AM to 5.30PM Heatingspares247.com is an Approved Spare Parts Stockist, and we guarantee to supply Genuine Heating Spares from the Boiler Manufacturers.