I have an Alpha 280e combi boiler. The boiler is currently set for DHW only, when I open the hot tap, the boiler fires up, hot water comes out of the tap at pressure. The problems start when I close the hot tap, the boiler fails to turn off and it continues to run, also the neon DHW light remains lit. Eventually the CH pipe under the boiler heats up. To solve this at present, after running the hot tap we switch the boiler off till we need hot water again.