Gloworm 30Cxi going cold using shower

[festive]

Noticed a problem last week when it went cold, F5 flashing on display, with the wonders of google, found i needed to remove cover and reset the stat top left and all seemed 'ok' after that.

Ive noticed a few times though lately the shower will all a sudden run cold then come back hot again, seems to be ever since this cold weather.
Also the drainage pipe does run in 22mm plastic i remember someone commenting on here before in cold weather that could be a problem causing a blockage is it all related? Any suggestions on what could be causing the cold running?

TIA

 

[ChrisR]

F5=overheating is probably caused by air in the boiler. Make sure the auto air vent cap is loose a couple of turns.

GOing hot and cold could be a few things, bu tthe most likely is sludge build-up on the boiler-water side of the hot water heat exchanger. They can be cleaned, but it's a corgi job because gas pipes have to be removed.

The condensate pipe should be insulated if there's any length of it outside - like more than a foot.