dhw works

Getting towards dhw in the House of Pain. Hot water source will be mains through a plate heat exchanger on the thermal store, supply pipe is 25mm into the house then 22mm to the hex. Pressure and flow both good. Bathroom 1 (6 metres) will have bath and overbath shower and basin Ensuite (16...

Boiler has developed this fault over the summer. Worked fine when CHS was on back in the Spring. Pressure is 1.5 All valves are open - pointing up Set to winter mode. Boiler fires up but after a couple of minutes stop and displays pump overrun. No error messages. Immediately under the boiler...