Neat not communicating with boiler

[JamesT]

Morning!

I have had my nest for about 2 years, running the radiators and hot water, all has been well until recently. The boiler would just not respond and ran constantly, I checked and found no lights on the heat link. When the heatlink was connected via the micro connection on the back, the heatlink light up with all the lights in green.

An electrician checked the power supply and found that it had power. He then swapped with the heatlink for the underfloor heating and found that it worked, so we assumed it was a faulty heatlink and returned the heatlink to the underfloor heating.

As I wanted it sorted it urgently, I forked out for a whole new nest system, replacing the heatlink and setting up the new thermostat. Despite several factory reinstalls, the thermostat and the heatlink are communicating, but it will not communicate with the boiler, I.e you can increase the temperature on the thermostat it goes organge but nothing happens!

The underfloor system is working perfectly, so the boiler is fine.

It’s really driving me insane so any help would be appreciated.

James 

[MarkSweeney]

Hi James,

I have a very similar story in that my Nest has been working perfectly for around a year, and all of a sudden it has stopped communicating with my heating system. 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 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 heat link and thermostat with no joy. My heating system is working perfectly when I manually switch my motorised valves to the open position. 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?

[AlexD]

Thank you for all the information @JamesT and @MarkSweeney . I am sorry to hear you are both facing similar behavior from your device. I would be happy to try and assist. 

As @MarkSweeney mentioned, a click test should be performed @JamesT.

Open the Nest app on the phone and stand next to the Heat Link. Make sure the display for the thermostat is black, heating off, and turn it up until it goes orange, heating on. Listen for a clicking noise and then turn the temperature back down until it goes back to black and listen for a clicking noise again. 

If it clicks in both cases that would indicate that the internal relay is switching as expected. If that is the case there are a few possible reasons for the valves not triggering. Some of them are:

1. The valves getting stuck or having wiring issues, not receiving the signal from the Heat Link.

2. Live power not being provided in the 2 terminal for heating or 5 terminal for hot water. 

3. The relays somehow not transferring the signal from the 2 terminal to the 3.

It would be best to get in touch with a Nest Pro installer or your preferred installer and perform a continuity test on the Heat Link to see if the relay works as it should. 

It would be best to do this live with my colleagues over the phone or chat and they can walk you, if you are comfortable in trying and have a multimeter, or the installer through the whole test. Here is the link with all our contact info. 

[JamesT]

Hi Alex,

Thanks for your reply!

So…

Yes I hear the clicking from the heatlink, when you adjust the temperature on the thermostat, however it doesn’t turn the boiler on.

An electrician has checked the wiring, but this is what they look like:

2nd picture is the underfloor 

First is the radiators and the hot water.

Thank you,

James 

[JamesT]

 

[JamesT]

 

[DragosC]

Thanks for the pictures. From what we've seen in here, it seems that one Heat Link is not wired accordingly, second picture looks alright for a combi boiler with hot water on demand. Just to confirm, the first picture is for the hot water and heating for one zone? 

[JamesT]

Thank for your reply!

The first picture (two white cables in) is for the radiators and hot water.

The second picture is just for the underfloor heating in the kitchen.

I have a system boiler set up, with a hot water tank.

Thanks for advice,

James 

[DragosC]

Thank you @JamesT. It seems the first one is not wired correctly. Do you have an S plan or a Y plan system boiler? 

[JamesT]

Morning @DragosC !

It is an S plan system.

Thanks,

James

[DragosC]

Thanks for letting me know, @MarkSweeney. That's great news. Could you tell me please if you've wired the second Heat Link accordingly to the page 22 of the installation manual? 

[MarkSweeney]

Sorry, I don’t have the instruction manual to hand. I’ve tried to find it online, but no joy so far. I would have followed the instructions that came with it, however, the Salus Distribution Box also had a wiring diagram to follow, so it may be that I used that diagram. I’ll take a snap of it tomorrow. If you have a link that I could download the instructions from that would be handy. I’ve tried on the helpmpages on. Nest.com , but can’t  see the instructions for the heat link install. 
I only had the one original Heat Link box, so I was slightly confused by your reply. I had a spare Honeywell Motorised 2 port valve, was that what you were thinking of? 

[DragosC]

Thanks. No worries. Here's the installation guide: https://bit.ly/3nt2N4t . Let me know when you've sent us the picture. 

[DragosC]

Hi there. I'm just following up on our last message. Do you still need our help? Keep us posted. 
 

[DragosC]

Since I haven't heard from you in a while, 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! 
 

[MarkSweeney]

Sorry for the slow response, it took me a few days to go out to get a multi 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 that I’m using, power was in fact 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? Perhaps the faulty valve was sucking all the power that would have gone to the H/W valve and prevented it operating properly? Odd, but after swapping the dead valve, picking the H/W was a luck break for me, all is working fine now and I have full control of my heating system via my Nest set up.

[MarkSweeney]

I meant to add I have a S Plan  system too. Slightly odd set up for me here,  in that I have a heat exchanger connected to a biomass system, but basically the motorised valve still does the same job, opens the C/H valve and kicks the circulation pump into life when it gets the call for heat signal from the Nest Heat Link box.