Client complained about hot water problems on Vokera Linea 24. At first sight it seemed like a blocked hot water plate giving following symptoms:

• hot water fluctuating between hot and cold – classic blocked heat exchanger symptom
• occasionally boiler would go to lock out and show error code E07 and would need to be reset manually
• error code 07 means ‘primary thermistor circuit open’. It means that primary circuit has exceeded it’s maximum temperature and as a safety device it stopped the boiler from operating.

I removed and cleaned dhw plate heat exhchanger on the first visit. This help to a point as water was no longer fluctuating hot and cold. However the boiler would still overheat and show and error code 07. I run boiler on central heating on maximum setting and boiler would overheat showing error code E 07 after about 3 to 5 minutes. Touching flow and return pipework inside the boiler confirmed poor circulation through main heat exhanger. There could be two reasons for poor circulation through main heat exhagner: blocked main heat exchanger or weak circulating pump. I removed pump head to find it blocked with sludge.

Removing top and bottom PCB to fit new selector switch:

Following repairs were done to this boiler:

• replace domestic plate to plate heat exchanger – removed fluctuating hot water problem
• replace failing circulating pump to improve circulation through main heat exhanger – removed overheating to the boiler and clears error code 07
• replace faulty selector switch on the boiler facia
• most important – remove underlying cause of pump and plate hex failure – sludged central heating system by power flushing to all radiators
• additional protection – installation of Magna Clean magnetic filter to further protect new boiler components

All in all this was a full days job to replace plate hex, install new pump, fix broken boiler selector, install magnetic filter and power flush the system. It should give this boiler few more years of life. Boiler with new filter installed below: