Nest 3rd Gen to replace Drayton LP241 , With no junction box

[jackalg1]

Hello

I want to replace a Drayton LP241 programmer with a Nest 3rd Gen , but ive noticed everything in wired directly into the LP241 ? . The Zone valve, Grunfoss Heating pump, and the Hot water tank cylinder stat ,roomstat etc . Im pretty confused as in my last house i only had half a dozen wires coming straight from a junction box etc, so it was pretty easy to install

many thanks

 

[ianmcd]

What a blooody mess, get someone in to fit a wiring centre and tidy that disgrace up, you will not cram all those wires into a nest receiver

 

[Dan Robinson]

A leaking mess too by the look of things.

 

[ianmcd]

A leaking mess too by the look of things.

But its only 240v wiring for the cyl stat that is laying in the leaking water so does that really count ? it is wiring for a water tank is it not

 

[jackalg1]

Nothing is leaking now the 3 pos valve was replaced before I moved in

 

[ianmcd]

Looks like the gate valve (Red handled valve in your pic) is leaking

 

[stem]

You may find that buried in the wall behind the Drayton is a back box that has been used as a junction box.

The Heat link replaces the Danfoss so they can be exchanged quite easily. The only problem you may encounter is if there are a lot of wires in the Drayton and not enough room to terminate them all in the Heat link. I which case you may find it easier to replace the Drayton with a junction box and then just wire single conductors from that to the Heat link terminals.

The Drayton wiring terminals have the following functions:

The existing wires are transferred from the terminals of the Drayton, to the Nest Heat link terminals that have exactly the same function.

Neutral, Live & Earth are straightforward
Drayton (1) Hot Water off = Heat link (4) Hot Water Satisfied
Drayton (3) Hot Water on = Heat link (6) Hot water Call for Heat
Drayton (4) Central Heating on = Heat link (3) Heating Call for Heat
Then terminals (L) (2) & (5) need to be electrically connected together

Don't worry if there aren't wires in every terminal, you will only need to use the wires that are present now.

The Nest Thermostat needs a 12v supply and can be powered either by using a separate plug in power supply, or by connecting terminals T1 & T2 of the Thermostat to the corresponding terminals at the Heat link.

Finally any existing room thermostat needs to be decommissioned, it can't just be disconnected otherwise the heating wiring would be permanently 'open circuit' and the heating would not operate. This is done by finding the origin of the thermostat cable, disconnecting it completely and then inserting a link between the terminals where the two thermostat live switching wires have just been removed from, so that they are electrically connected to complete the circuit. Alternatively as a temporary measure setting the existing room thermostat to maximum / permanently on, will prevent it interfering with the operation of the Nest