New Nest install Hot Water not working

[Mighty_Genghis]

Hi all,

Bit of a desperate plea. We had a Nest installed yesterday and today have realised it isn’t firing the hot water. I’ll get in touch with the electrician and hopefully he can get back here over the weekend (three young kids so hot water is an essential!)

When he installed it the units battery was flat so he couldn’t test with it live.

In the meantime I did my part p a few years ago and have done plenty of wiring so am hoping someone can spot a simple wiring change that is required. We’ve got an oil boiler and hot water tank.

Wiring centre photo attached, so is there an obvious error ? When the hot water is turned on on the controller there is a click in the heat link but nothing else happens. Central heating works fine




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[Someone-Else]

Not 100% sure, but in the mean time what happens if you move the lever on the valve?

[Mighty_Genghis]

I’ll have to check in the morning as the baby is asleep in that bedroom at the moment , do you mean a lever on the bottom of the 3 way valve ?


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[Someone-Else]

Yep, that's the one. (Not sure if it goes in the middle or the other end, but you can move it.)

[Mighty_Genghis]

Just snuck in there, the lever moves freely


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[Someone-Else]

Yes, but did the hot water come on?

[Mighty_Genghis]

No nothing, pump isn’t running either and I don’t think the boiler is firing either


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[Mighty_Genghis]

This lever



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[Someone-Else]

I only asked about the lever to see what would happen as it is a diverter valve.

I have no idea what wiring diagram he is using, may be the nest one? its not the one you have taken a picture of (look at 8 & 13, the drawing shows they should have wires...........they don't) since they have no wires, (He may have used the unlisted choc bloc in the middle ) and as I have no idea what the white flex next to the valve flex and what the last white flex is for I am unable to help you.

[Mighty_Genghis]

Not sure if it helps but the cables from left to right are
Valve
Nest
Boiler 4 core
Mains supply
Pump
Cylinder



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[Mighty_Genghis]

Just found something odd, if I turn the hot water tank thermostat down passed the click point then the hot water fires up. Could that mean it’s as simple as the demand and satisfied cables are the wrong way around ?


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[Someone-Else]

Its worth a try

[Mighty_Genghis]

The electrician just left after an hour of diagnosing, his conclusion was that the supplied wiring diagram with the nest has the terminals the wrong way around for the hot water tank thermostat. He’s now put 1 in 2 and vice versa and all is working

Now on to Nest to try and get them to pay for his diagnosing time !


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[Someone-Else]

Can you post a copy / picture of the nest diagram?

[Mighty_Genghis]

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