Nest has stopped controlling my heating system

[MarkSweeney]

 my Nest system has been working perfectly for around a year, and all of a sudden it has stopped communicating with my heating system a few days ago. All seems well on the thermostat, showing heating in progress, but it’s not actually opening the motorised valves which in turn would activate the pump to circulate the hot water  in my  central heating circuit, or hot water tank. The light on my heat link is green and seems to be communicating with the thermostat as usual. The heat link makes a click sound when you activate the system manually by pressing the big centre button, however it doesn’t control the motorised valves as it should. I’ve tried a reset on both 3rd gen heat link and the learning thermostat with no joy. My heating system is working perfectly when I manually switch my motorised valves to the open position, so all seems fine at that end of the system. Equally, there are no errors messages or apparent problems with the Nest side of things, but they just have stopped talking to to each other and there is no heating or hot water switch on. It’s so weird and driving me nuts. It just happened a few days ago after working perfectly sine the install. I wonder if there has been some kind of update recently?

[Frustratedddd · Accepted solution]

A simple test to prove the relays are opening and closing is with a neon screwdriver, do you have one?

Should the answer be yes, starting from the heating and water being off, [not calling for] Term 1 should be live and Term 3 should not. Term 4 should be live and Term 6 not. Now turn your display to call for heat, the reverse should now be, 1 not live and 3 live, 4 not live and 6 live.

Does that help?

There was an update back in November time, but I don't think that would have caused this issue.

[MarkSweeney]

Good idea. I don’t have a neon screwdriver, but I can work around that. I’ll give that a go. Seems odd that that both relays for hot water and heating would fail at the same time, but its a good way to find out. Many thanks, Mark

[Frustratedddd]

Tester is better, just thought everyone has a neon in the drawer.

They may not have failed, you are proving if they are working or not!

[MarkSweeney]

Sorry for the slow response, it took me a few days to go out to get a tester, but it was well worth it. After checking the power supply to the terminals you suggested and following those connections through to the Salus Dirstribution Box I’m using, power was reaching both my motorised valves for H/W and C/H. I had a spare Honeywell motorised valve, so a swapped that out for the Central Heating valve and hey presto, I was back in business! Both my motorised valves sprang back into life. Clearly the C/H valve was faulty, and perhaps with some of the wiring being in common connectors, within the Salus Distribution box,  had affected the operation of the H/W valve, who knows?

All is working fine now and I have full control of my heating system via my Nest set up. Many thanks for the idea of checking the power supply to the valves after hearing the “click”from the Nest Heat Link box. Kudos applied Sir!

Many thanks again,

Mark

[DragosC]

Hi there all,

Thanks for your help on the matter @Frustratedddd. I'm glad it's been sorted out. In this case, , I'll have to close this thread. Should anything else come up, please open another thread and we'll take it from there. Have a good one and stay safe!