Nest not heating hot water independently of central heating

[BarrelOfOtters]

It was fine, till a few weeks ago, now to get the water to heat we have to put in on manual that also puts the heating on. It's annoying (even thought I've turned the radiators off).

I've tried resetting, I rang Nest and they said i had to get an electrician to look at the boiler, I did and annoyingly while he found another problem he didn't sign the bit of paper for Nest.

Anyway....anyone else had this?

I've not had this and I don't have Nest myself.

But... as I understand it (seriously correct me if I'm wrong!) Nest just replaces your thermostat, from a clicky/rotary thing to a smart/app based thing. It doesn't replace either the controller (where you time the heating and hot water to come on at certain times) or the zone valves that actually control your central heating.

I would suspect either the central heating controller needs to be replaced, or the zone valve that controls the flow of hot water to the radiators is faulty (maybe stuck in the open position).

Scratch that, I've just seen Nest can replace your controller aka programmer so it could be one or the other. Sorry, just my lack of knowledge where these smart things are concerned.

Some possibilities:

1. Nest is turning on your radiator circuit when it shouldn't be
2. Nest isn't faulty, but your existing programmer (if you have one) is turning on your radiator circuit when it shouldn't be
3. Zone valve is stuck open, meaning water is permanently flowing to the radiator circuit even when only hot water is supposed to be on.

I've personally had both 2 and 3 in the past, without bringing something like Nest into the equation.

@MaybeSmaller thank you. You may be right. Was it a plumber or electrician that sorted you?

It was a gas/heating firm that sorted the zone valve for me and they should be well placed to diagnose other faults in the system as a whole. Someone who's purely set up as an electrician or a plumber may only be able to look at one part of it.

The faulty programmer was a DIY job (just unscrew old one and fit new one to existing plate. Nothing complicated)

We don’t have Nest.
But our system has done similar several times over the years, it was a “two way port valve” little grey box thing gets stuck and needs replacing.
Oil fired boiler.

This happened us last year. We have an old system - boiler in the loft, hot water tank etc.

Used Nest for 2 years and the hot water randomly stopped. It turned out the Nest receiver on our boiler wasn’t receiving the signal. We ended up swapping to Hive which we’ve had no issues with since installation

Exact same thing for me.

Thanks all, fixed now, it was a valve.