Nest thermostat not heating water

[Jkins]

Hi - my nest thermostat no longer fires the boiler or makes the relay clicking noise when set to boost or schedule. The radiator heating works fine when dialled up, this is the only way to get hot water now for showers etc. can someone please advise how to fix this? 

[Frustratedddd]

Are you in the UK, and have a Heat Link?

[Jkins]

Hi - no I’m in Ireland but yes have a heatlink. 

[Frustratedddd]

Sorry I should really put EU/UK, but you have the Heat Link so we are on the right page.

Just to confirm, are you saying you have lights on the Heat Link, and the heating is working fine as normal with the thermostat operating the Heat Link to turn on the heating?

Are you saying if you press the Heat Link button you cannot get hot water, or via the app boost?

Do you have motorised valves in the system and have you checked them?

[Jkins]

Hi - yep, have two heat links and two smart stats for separate zones and water. 

The heatlink appears to work as normal for the radiator heating, but nothing happens when  I schedule or boost water from stat or app, I have motorised valves on all 3 zones, water included, and they all seem to be working fine but I cannot test the water one due to this problem. I have the water motorised valves in manual open mode so it heats when rad heating is on, just to have hot water for showers etc, but this means dialling up heating just to get hot water. 

The problem appears to be that the stat isn’t calling the boiler or switching the motorised valves for the hot water when called from app, stat or heatlink. 

Am I making sense??

[Frustratedddd]

 Lights on ALL the Heat Links?

9/10 I would say it's the valve, but assuming you are saying they are working???

Are you OK with a screwdriver and do you have any means of testing? A simple neon screwdriver will do?

[Jkins]

Yes all green - when I press center button then all lights light up on heatlink also. 

[Frustratedddd]

Do you have a neon tester or any form of tester?

[Jkins]

Yes I have a screw driver tester or multi meter. 

[Frustratedddd]

OK, this will confirm the relay is working for your hot water. Remember all the terminations under the Heat Link cover are live, so proceed with caution.

Make sure you have just one green light on the H/L
Make sure the hot water schedule is disabled, go to………. Settings – hot water schedule – disable.

Remove H/L cover, you will see connections N – L – 1 – 2 – 3 – 4 – 5 – 6 the others we are not interested with.

Place the neon tester onto termination No 4 – the neon should be bright
Place the neon tester onto termination No 6 – the neon should be dull
Keep the neon tester on termination No 6 and at the same time press the H/L button

You should hear a click and the neon tester will be brighter like termination No 4 was, and the H/L should have 3 lights

Just to prove, remove the neon tester from termination No 6 and place on termination No 4, that should now be dull

Should that all work as described then the Hot Water relay is switching and working correctly.

Let us know how that goes

[Jkins]

Ok - so with cover off on the water side i have connections on 5 and 6 only. With water schedule off and not boosting I have current on 4, 5 and dull 6. When pressing HL button I then have dull 4 and bright 5 and 6. Relay seems to be pulling in fine also, clicking away same as other HL. 
is the wiring incorrect if I have nothing terminated to 4? 

thanks 

[Jkins]

I also noticed I have nothing wired to thermostat T1 T2, instead this appears to be wired into my hot water motorised valve to turn on/off the power based on stat being open or closed depending on water temps. Is that correct? 

[Frustratedddd]

T1 -T2 are 12v connections to power the display. The base plate if you look has the same connection markings. You obviously are wireless connections to your display, ie display on a stand fed by a usb lead.

You say you have connections from those going to the motorised valve correct? 

 When was the thermostat installed 

[Frustratedddd]

Yes that is correct and you have proved the heat link is working on that hot water section relay. Working as it should.

See the picture of the wiring to confirm.