HELP! NO HOT WATER. Nest learning thermostat and heat link.

[stu3yp]

Hi Guys,

I am new here and have joined to try and get some help. 

I have a Worcester Bosch Greenstar 18ri. It is less than 2 yrs old and was installed at the same time as my nest learning thermostat and heat link. 

I have a mega flow system located upstairs and no water tank etc in the loft.

Everything was working fine with my nest until about 2 weeks ago when suddenly I had no hot water. I got notification from Google telling me my heat link was not working, which had in turn caused my thermostat battery to die.

I charged the thermostat without issue however had no power to the heat link. 

Google replaces the heat link a few days ago, however since then I have not been able to get any hot water. 

I have noticed the app no longer turns orange when boosting or putting hot water on via schedule. Every so often it does go orange, but most of the time remains grey and just says ON.

When the water is turned on, I hear a click on the heat link but the boiler does not fire up.

From searches it appears a lot of people have had the same issue and have had a motorised valve replaced. It just seems a big coincidence that this all happened at once. 

Any help would be greatly appreciated. I have emailed Google without a response so far, and I refuse to believe that this isn't all related. 

[Frustratedddd]

The first thing you need to check is the Heat Link has been installed correctly. Maybe obvious, but many people get it wrong. Just have a double check. Then if all is OK, get a neon tester on the contact number 6 and see if it comes live when calling for H/W, and off when not. Check also, when not calling for H/W contact number 4 is live, and live when switched to not calling for H/W. These 2 contacts switch between each other.

That will prove one thing if the Heat Link is good or faulty.

Regarding the greyed out icon on the H/W, that is very common, and I have argued for years to Nest to get that glitch sorted out, but after 4 years still nothing from Google. I expect your heat icon still goes orange though as before?

[stu3yp]

Hi, thanks for the response. I will buy a neon tester. 

I took pictures of the old one wired up, and it appears to be wired the same. 

Randomly my heating just came on when it should be off. I checked the stat and found the yellow flame for bacteria prevention showing. 

Not sure if that indicates something is wired wrong, as the heating seems to activate fine when I press it on the app.

[stu3yp]

I contacted nest and they suggest that my poet valve is sticking. Both seem to move freely but the hot water one just doesn't seem to activate.

I wondered if it was the motor so have swapped the motors and the heating still works so the motor was fine. 

Sadly the hot water still does nothing.

Does this mean it is not getting power or that the valve itself could be stuck under the head. 

What will happen if I swap wires 3 and 6 on the heat link?

[Frustratedddd]

The first thing you need to do is check the contacts are switching on the heat link. Without them switching you will not get power to the other parts.

Swapping those terminals over just switch the other way, ie normally open to normally closed.

[stu3yp]

Hi, thanks for the reply. I haven't managed to get a neon tester yet as been working shifts 

I have just taken off the head to see if the valve was stuck and it moved freely by hand.

I also checked all the wires for any loose connections and all seem good. Upon putting it all back together the hot water started to work as it should.

Turned it on and off a few times and seemed fine.

However now it's not working again. Will it only fire up if it needs heating. So if its already at temp the valve won't come on?

[Frustratedddd]

Not knowing your system, I cannot answer that.

I would think if the system worked, then I would assume the heat link is switching. I would still confirm the contacts are working as my first job.