I am after a bit of advice. Had a sparky fit a Nest thermostat today. All seemed to be working fine when he left. However this evening things are going wrong.

We have a conventional boiler (Potterton Suprima) and it came on to heat the water and then when it turned off everything clanged like Quasimodo having a fit. Its never done this before. After this the boiler was out and needed resetting. Subsequently it will light when the thermostat asks for the heating but not the hot water. It seems OK for a while but when it shuts off it clangs all the pipes and the boiler itself shudders for a few seconds and then it may or may not need resetting.

Obviously I have contacted the engineer that fitted the nest (he was organised by nest themselves but I had his mobile number) he’s promised to raise it with the office in the AM but I am keen to see if there is anything I can do in the meantime given that we are so close to Xmas and about to have a houseful of guests.

Possibly water hammer or your hot water cylinder is way too hot?

The Nest is just an electric switch, so I’m struggling to see how it could affect the physical plumbing of your house.
Happy to be educated otherwise though.

My guess is he’s not got the thermostat on the cylinder right so the boiler is over heating and tripping out

Yeah, sounds like he has either messed with something he shouldnt have or he has wired it incorrectly.

The latest NEST should be able to do hot water and heating with no issues.

Its all turned off now to stop any issue getting worse. Hopefully they can get someone over tomorrow/Sat to rectify otherwise Xmas is cancelled 😉

Possibly water hammer or your hot water cylinder is way too hot?

That would need the return temp thermostat in the boiler to fail. You can’t boil water in a tank using indirect heating as that would need the heating coil water to be at 100C or over and the boiler will cut out long before then.

The juddering could be air in the system as in air lock or possibly the pump is being switched off but not the boiler and the residual heat in the heat exchanger is boiling the small amount of water in the heat exchanger (i.e. pump over run isn’t working). Our 30 year old Potterton suffers from a bit of Kettling when the pump switches off (no over run).