Swapping Drayton SCR and Thermostat for NEST

[aidan88]

Good Morning,

Our Valiant timer on boiler has packed in an additionally the Drayton thermostat and reciever has stopped working (I have replaced the batteries and tried moving closer, it had been in the same place for years anyway).

We have been thinking of switching to a Nest anyway, would this transition be simple? Presumably do away with the digital Drayton thermostat downstairs and fit the Nest where the existing receiver is? Would this solve our broken timer and receiver issues to? Seems pointless replacing the timer on the boiler if this is what we wanted anyway...

I have attached a photo of the current wiring behind the reciever.

Many thanks and please excuse any ignorance on my part!

A

 

[stem]

Provided that the failed boiler timer can be left in a permanently 'on' setting then Nest can provide time and temperature control in a single unit. You don't mention any hot water control, so I take it that you have a combi boiler.

The Drayton SCR receiver wiring is as below:

There are different versions of Nest, so I'll assume you are referring to the most common which is the 'Nest 3rd Gen' as per the diagram below.

If it's another version such as Nest-e than post back

With Nest 3rd Gen it's just a matter of moving the wires from the Drayton receiver to the Nest Heat link terminals that have exactly the same function. So:

Wires in Drayton N = Heat link N

Wires in Drayton L = Heat link L

Wire in Drayton 1 'Common' = Heat link 2 'Common'

Wire in Digistat 3 'Call for Heat' = Heat link 3 'Call for Heat'.

The Nest thermostat requires a 12v DC power supply, and terminals T1 & T2 of the Nest Heat link provide this. There are corresponding terminals marked T1 and T2 in the thermostat. If this cable doesn't exist it will need to be installed, or alternatively Nest sell a plug in power supply to power the thermostat as an option if you don't want to run a new cable.

EDIT
As an afterthought, if you went for a Hive Single Channel instead of Nest, it would fit straight on the existing backplate without any re-wiring and the Hive thermostat is battery operated so no additional wiring or power supply required.

 

[aidan88]

Yes, at the time of writing this I thought you had to pay a subscription for Hive, but realise this is not necessary and have since wondered if a Hive would be a more straightforward installation/swap.

You are correct, it is a combi boiler (hot water is working but heating currently off due to faulty reciever). Then timer on the boiler can indeed be set to on opposed to timer.

Thanks for your help, that's great.

Aidan

 

[hovertoast]

I’ve just done the exact same swap as my Drayton also packed in. Two weeks into the Nest and I’m really happy with it. Bought the official stand with included power cable and using the thermostat wirelessly.

Took me less than 10 mins to install. Make sure you ensure electrics are safely isolated before working on anything, as you can never be certain other supplies aren’t feeding the same thing for example.