Wiring Nest 3rd gen to Vaillant turboTEC plus

[Sup9]

Hi, I'm looking to install a Nest 3rd gen thermostat for my dad's house. His boiler is Vaillant turboTEC plus and wired to another room with controller/thermostat (VRT 330).

Did some search on the forum and I believe I need to:
1. wire the boiler L/N to heat link L/N;
2. Take off pin on boiler 3/4 and wire to Heat Link 2-3;
3. either use 7/8/9 connects to heat link T1/T2/E or I can run the Nest thermostat on usb power and just remove the cable from boiler connector 7/8/9 (prefer the later as the current thermostat is behind curtain).

But looking at the Nest Heat Link connectors, 1-3 is for heating, 4-6 is hot water. So if I wire it as above, what's controlling the hot water? The control panel on the boiler sets the water temp for hot water and heating separately but I don't see any wires for hot water that I can run into the heat link?

below is the current setup:

View media item 103623View media item 103624View media item 103625View media item 103626

 

[Mac moc]

Hi, did you manage in the end? Mind posting a picture of how you wired the heat link to the boiler please?

 

[Sup9]

Hi, did you manage in the end? Mind posting a picture of how you wired the heat link to the boiler please?

I haven’t figured out how to wire the hot water so didn’t install the thermostat- might just wait until I replace the boiler as I don’t think it’s worth it for me without hot water control.

 

[Deleted member 267285]

If either of yours are combi boilers, then you wouldn’t wire nothing in for the hot water. Opening a cover on these types of boiler is work defined in the gas regulations, and therefore subject to certain safety checks.

 

[stem]

The boiler in the OP's photograph looks like a Combi boiler, so usually there isn't any hot water control required. Opening a tap heats the hot water instantly upon demand. The VRT thermostat is connected to the 24 VDC terminals 7, 8 & 9 as can be seen below. I believe that the VRT 330 is rather unusual for a UK installation, so maybe why no one has replied.

The Nest Heat link terminals 2 & 3 would be connected to boiler terminals 3 & 4 after the red link is removed as per the diagram from the Vaillant manual which shows 'generic' external controls wired to these terminals

The Heat link also requires a 230V supply connecting from the boiler L & N

With some types of boiler it is necessary to open a 'room sealed' compartment to access the boiler's wiring terminals, where this is the case, this is not a DIY job and should only be done by a RGI (Gas Safe Engineer) who can carry out the necessary safety checks to make sure that it is properly sealed up again afterwards. I can't remember if your boiler falls into this category or not. Some Vaillant's don't but I can't be sure from memory.

Regarding Hot water control. This would normally be for a system that has a hot water cylinder attached. In which case there is usually a programmer fitted that provides individual time control for the Heating and Hot Water. When this is the case, installation is different, the Nest Heat link replaces this programmer and is not connected to the boiler directly.

 

[Deleted member 267285]

With some types of boiler it is necessary to open a 'room sealed' compartment to access the boiler's wiring terminals, where this is the case, this is not a DIY job and should only be done by a RGI (Gas Safe Engineer) who can carry out the necessary safety checks to make sure that it is properly sealed up again afterwards. I can't remember if your boiler falls into this category or not. Some Vaillant's don't but I can't be sure from memory.

Yes it does, it forms part of the combustion circuit.

 

[stem]

OK, there you go then, thanks for the confirmation.

Some Vaillant's have an external drop down door that allows direct access to the wiring connections without opening up the combustion chamber. This obviously is not one of them.