Nest thermostat not controlling hot water

[Immortanjo]

Hey guys,

I just installed a nest thermostat 3rd on my vaillant combi boiler ecotech pro 28 (286-33) and the heating control works fine. I followed the wiring from another post here: https://www.diynot.com/diy/threads/...neration-vaillant-ecotec-pro-28.454693/page-3

However, I can't control the hot water as it's always on with the heating.

I've attched the pictures from the boiler manual and the wiring of the heatlink. I know something is missing but I just can't figure out what. Could you guys let me know what's wrong?

Many thanks

 

[CBW]

I take it you don’t know how a combi boiler works? Hot water is provided on demand - providing there’s no issues/faults. You don’t control it via a Nest or any other room thermostat.

 

[Immortanjo]

I take it you don’t know how a combi boiler works? Hot water is provided on demand - providing there’s no issues/faults. You don’t control it via a Nest or any other room thermostat.

Thanks for the reply!

It is a bit confusing to me yeah.

I did an experiement earlier today:
1) heating adjustment knob MAX - Nest heating OFF - radiator OFF
2) heating adjustment knob MIN - Nest heating ON - radiator OFF
3) heating adjustment knob MAX - Nest heating ON - radiator ON

So I came up with the conclusion that Nest just cut the power when the room temp reaches the set temp. Thus I assumed it could be the same with the hot water? It's off by default but I could turn it on by pressing the hot water (boost) button?

 

[ianmcd]

And exactly how do you think the nest senses the temperature of the Hot water ? or is it not a combi boiler ?

 

[Immortanjo]

And exactly how do you think the nest senses the temperature of the Hot water ? or is it not a combi boiler ?

I understand that it cannot know the water temp but can it be used as a on/off switch for the hot water?

 

[bhm1712]

With a combi boiler, the hot water is on demand. There is no on and off control. You’re not heating a hot water cylinder. You turn the hot tap on and the boiler turns on and heats the hot water to whatever temp you’ve set the boiler to for hot water. The Nest does not control that and there is no on and off control via the nest for hot water.

 

[BlueLoo]

That wiring is terrible!

I'd have put in a wiser combi control system with smart rads. Something specifically designed for combi's.

 

[RandomGrinch]

That wiring is terrible!

I'd have put in a wiser combi control system with smart rads. Something specifically designed for combi's.

Yes, that wiring is truly terrible.
Luckily the photo is from the linked post in 2018.
Hopefully the OP's wiring will be a lot better

 

[ianmcd]

Post a pic of your own setup, not someone elses