Drayton LP241 to Nest 3rd Generation

[Zee Hyde]

Hi All,

I am trying to replace Drayton LP241 with Nest 3rd Generation but not sure on wires as I have only 5 wires in existing base so need to understand which wire needs to go where.

Your help will be appreciated, please see pictures below:

Existing Drayton Picture


Drayton Wiring


Drayton Backside


Nest


Existing Thermostat



I also need to change thermostat with Nest so need you help in replacing both, i will appreciate if someone can guide which wire needs to go where with diagram.

 

[stem]

You have provided the information that you need. The wires now going to the Drayton LP are connected as follows....

....they are moved from there to the Nest Heat link terminals that have exactly the same function. So:

The wires in N and L are straight forward, they go to the corresponding terminals at the Heat link.

The wire in LP HW OFF (1) will move to Heat link 'Hot Water Satisfied' (4)

The wire in LP CH ON (4) will move to Heat link 'Heating Call For Heat' (3),

The wire in LP HW ON (3) will move to Heat link 'Hot Water Call For Heat' (6)

Only the wires that are presently there need to be moved, so don't worry if some terminals are left vacant.

Links are then required between (L) and the two 'Common' terminals (2) and (5) so that the 3 terminals are electrically connected.

The old thermostat needs to be decommissioned. It can't just be disconnected. This is done by tracing the old thermostat cable back to its origin. Note where the wires are connected and disconnect them. Then insert a link to join together the two terminals that you have just removed the thermostat wires that used to go to the (L) and (3) terminals of the thermostat from so that they are electrically connected.

If this is difficult to do, as an option, the old thermostat can be left in place and the wire in (3) moved into terminal (L) with the other wire already there.

The Nest thermostat can be powered using a separate plug in power supply, or by running a new wires to connect the Thermostats T1 & T2 terminals to the same terminals at the Heat link.

 

[Zee Hyde]

You have provided the information that you need. The wires now going to the Drayton LP are connected as follows....

View attachment 180172

....they are moved from there to the Nest Heat link terminals that have exactly the same function. So:

The wires in N and L are straight forward, they go to the corresponding terminals at the Heat link.

The wire in LP HW OFF (1) will move to Heat link 'Hot Water Satisfied' (4)

The wire in LP CH ON (4) will move to Heat link 'Heating Call For Heat' (3),

The wire in LP HW ON (3) will move to Heat link 'Hot Water Call For Heat' (6)

Only the wires that are presently there need to be moved, so don't worry if some terminals are left vacant.

Links are then required between (L) and the two 'Common' terminals (2) and (5) so that the 3 terminals are electrically connected.

The old thermostat needs to be decommissioned. It can't just be disconnected. This is done by tracing the old thermostat cable back to its origin. Note where the wires are connected and disconnect them. Then insert a link to join together the two terminals that you have just removed the thermostat wires that used to go to the (L) and (3) terminals of the thermostat from so that they are electrically connected.

If this is difficult to do, as an option, the old thermostat can be left in place and the wire in (3) moved into terminal (L) with the other wire already there.

The Nest thermostat can be powered using a separate plug in power supply, or by running a new wires to connect the Thermostats T1 & T2 terminals to the same terminals at the Heat link.

Thanks for your response, really appreciate. I fully understand now on replacing base.

Regarding thermostat, I have taken picture of all wiring so can you please guide me on what wires need to be disconnected or connected to replace existing thermostat with Nest.



I will appreciate if you can explain, exactly the way you did for Nest Base.

Thanks again in advance

 

[stem]

According to the lid legend, the two room thermostat cables should be connected to terminals 2 & 3

However, as is often the case, the original installer has ignored that and done his own thing. As you can see, there isn't a wire in terminal 2

So unfortunately, it will need to be traced either physically, or by someone competent with a multimeter who can identify the wires using electrical testing. The choice of wire colours and terminations are down to the personal preferences of the original installer and the cables they have to hand so it's impossible to say which wires they are when I can't see where they are connected at the other end.

I suspect it will be this cable, but without testing it I can't say for certain.

If you are able to use a multimeter or know someone that can, a simple test of the wires would confirm. You would be looking for a live that appears on the red wire in 3 only when the heating is switched 'on' at the programmer. And a switched live on the yellow in 9 that is live when the thermostat is switched up, and not live when it's switched down.

 

[Zee Hyde]

According to the lid legend, the two room thermostat cables should be connected to terminals 2 & 3

View attachment 180195

However, as is often the case, the original installer has ignored that and done his own thing. As you can see, there isn't a wire in terminal 2

View attachment 180196

So unfortunately, it will need to be traced either physically, or by someone competent with a multimeter who can identify the wires using electrical testing. The choice of wire colours and terminations are down to the personal preferences of the original installer and the cables they have to hand so it's impossible to say which wires they are when I can't see where they are connected at the other end.

I suspect it will be this cable, but without testing it I can't say for certain.

View attachment 180198

If you are able to use a multimeter or know someone that can, a simple test of the wires would confirm. You would be looking for a live that appears on the red wire in 3 only when the heating is switched 'on' at the programmer. And a switched live on the yellow in 9 that is live when the thermostat is switched up, and not live when it's switched down.

Million thanks, it does all make sense. I will check with my friend as he is electrician and will follow as you said.

Thanks again. I will get back if any further assistance needed meanwhile have a lovely weekend.

 

[Zee Hyde]

According to the lid legend, the two room thermostat cables should be connected to terminals 2 & 3

View attachment 180195

However, as is often the case, the original installer has ignored that and done his own thing. As you can see, there isn't a wire in terminal 2

View attachment 180196

So unfortunately, it will need to be traced either physically, or by someone competent with a multimeter who can identify the wires using electrical testing. The choice of wire colours and terminations are down to the personal preferences of the original installer and the cables they have to hand so it's impossible to say which wires they are when I can't see where they are connected at the other end.

I suspect it will be this cable, but without testing it I can't say for certain.

View attachment 180198

If you are able to use a multimeter or know someone that can, a simple test of the wires would confirm. You would be looking for a live that appears on the red wire in 3 only when the heating is switched 'on' at the programmer. And a switched live on the yellow in 9 that is live when the thermostat is switched up, and not live when it's switched down.

Hi Stem

Thanks for your response, I did some investigation manually and manage to find out below, highlighted/tagged in picture




N from Drayton is going to N in middle
L is going to L below 7 number
1 is going in 6
3 is red cable that is coming from cable from wall as highlighted
4 is going in 3

I suspect/pretty sure that blue highlighted cable is the one that goes to thermostat connection and as you stated

Red is going in 3 in box and going in L in thermostat
Yellow is going in 9 in box and going in 3 in thermostat
Blue going in N as circled in box and going in N in thermostat
Earth cable is not connected in box but going in E in thermostat

Please suggest what I need to disconnect in box and what I need to do.
Cable that is running to old thermostat what connection do I need to give on both sides i.e. connection to NEST thermostat T1 and T2 and on other side from box to nest hub

Thanks and sorry for the hassle

 

[Zee Hyde]

Hi Stem,

Good morning, can you please check below and confirm if that is correct to do

Connecting Heat Link

• The wires in N and L go to the corresponding terminals at the Heat link.
• The wire in LP HW OFF (1) will move to Heat link 'Hot Water Satisfied' (4)
• The wire in LP CH ON (4) will move to Heat link 'Heating Call For Heat' (3),
• The wire in LP HW ON (3) will move to Heat link 'Hot Water Call For Heat' (6)
• Link between (L) and (2)
• Link between (2) and (5)

Disconnect Old Thermostat by doing below:

1. Disconnect Red from 3 which is going to to (L) in thermostat
2. Disconnect Yellow from 9 which is going to (3) in thermostat
3. Disconnect blue from N which is going to (N) in thermostat
4. Link between (3) and (9)

Connecting Nest Thermostat

1. Connect disconnected red wire from (3) to T1 in heat link
2. Connect disconnected yellow wire from (9) to T2 in heat link
3. Connect wires in similar order on other side in thermostat T1 and T2

 

[stem]

That looks good to me, well done in working it all out! And I'm glad my assumption about the thermostat cable was correct.

Red is going in 3 in box and going in L in thermostat
Yellow is going in 9 in box and going in 3 in thermostat

1) Remove the red thermostat wire from terminal 3
2) Remove the yellow thermostat wire from terminal 9
3) Move the brown wire in terminal 3 to terminal 9 [this is instead of the link, but does the same thing]

Blue going in N as circled in box and going in N in thermostat
Earth cable is not connected in box but going in E in thermostat

These wires are just disconnected, no other changes required

Please suggest what I need to disconnect in box and what I need to do.
Cable that is running to old thermostat what connection do I need to give on both sides i.e. connection to NEST thermostat T1 and T2 and on other side from box to nest hub

All of the wires to the old thermostat will now be disconnected at the wiring centre, and you can remove them. Now you can either use the old thermostat cable assuming it goes to where you want it, or run a new cable to connect T1 at the Heat link to T1 at the Nest thermostat and T2 at the Heat link to T2 at the Nest thermostat.

If you are going to use this method to power the thermostat instead of a separate power supply. The Nest Heat link requires an earth connection to its earth terminal which is next to T1 & T2

Edit
Looking at your last photograph, some of the wires from the wiring centre to the programmer are what is known as 'singles'

Where wires cross from accessory to accessory, they should have an outer sheath for protection, like the white cable. This would be a good opportunity to replace them with a sheathed cable.

 

[Zee Hyde]

That looks good to me, well done in working it all out! And I'm glad my assumption about the thermostat cable was correct.



1) Remove the red thermostat wire from terminal 3
2) Remove the yellow thermostat wire from terminal 9
3) Move the brown wire in terminal 3 to terminal 9 [this is instead of the link, but does the same thing]



These wires are just disconnected, no other changes required



All of the wires to the old thermostat will now be disconnected at the wiring centre, and you can remove them. Now you can either use the old thermostat cable assuming it goes to where you want it, or run a new cable to connect T1 at the Heat link to T1 at the Nest thermostat and T2 at the Heat link to T2 at the Nest thermostat.

If you are going to use this method to power the thermostat instead of a separate power supply. The Nest Heat link requires an earth connection to its earth terminal which is next to T1 & T2

Edit
Looking at your last photograph, some of the wires from the wiring centre to the programmer are what is known as 'singles'

View attachment 180316

Where wires cross from accessory to accessory, they should have an outer sheath for protection, like the white cable. This would be a good opportunity to replace them with a sheathed cable.

I just implemented it and it is perfectly working find so huge thanks for saving my £100.

Please see picture below of my work



Regarding sheathed cable I will do it next time as I am still learning and did not had cables handy.

Once again million thanks and God bless you

 

[stem]

I just implemented it and it is perfectly working find so huge thanks for saving my £100.

And the satisfaction of achieving it yourself....priceless

 

[Zee Hyde]

And the satisfaction of achieving it yourself....priceless

Indeed that feeling is priceless.

After 24 hours monitoring, I have noticed heating is working perfectly but it seems some issue with hot water as I get very luke warm water a d not fully hot.

I turned on hot water for 3 hours but still same, so seems it turns on and then turn off and then keep repeating.

I opened box and saw link from L to 5 was loose as you can see below



I have inserted cable properly and also remove link from 3 to 9 as you suggested and inserted cable in 9 along with black.



I hope the loose cable was the issue for water not getting hot properly. I will monitor and will update you. If you have anything in mind please do share.

Thanks in advance

 

[ianmcd]

I opened box and saw link from L to 5 was loose as you can see below

Link should be from L to 2 & 5 I cant see anything in 2

 

[stem]

I think it's a parallax error due to the angle of the photo. I really struggle with photos of Heat links. Look how far across the wire to the L terminal appears.

Using the same dimension, the second wire I've highlighted is actually in terminal 2. However, terminal 2 is related to the central heating (which is working) not the hot water.

I have inserted cable properly and also remove link from 3 to 9 as you suggested and inserted cable in 9 along with black.

That wiring is to do with the control of the central heating, so if the heating is working all is well there

The loose wire in 5 is probably the culprit that is associated with the control of the hot water.

You can test it by pressing the button in the centre of the Heat link, so that the 'drip' Hot Water Light symbol is illuminated.

If the hot water heats up then, the wiring is OK. During the test the heating will be permanently 'on' also and the Nest thermostat won't operate it. But if you check the pipe from the motorised valve to the hot water cylinder, you will be able to tell pretty quickly if the hot water is flowing from the boiler to heat the hot water cylinder. Be careful not to burn your finger!

 

[Zee Hyde]

I think it's a parallax error due to the angle of the photo. I really struggle with photos of Heat links. Look how far across the wire to the L terminal appears.

View attachment 180427

I will do the test and will get back and thanks again as you are a great teacher/mentor

Using the same dimension, the second wire I've highlighted is actually in terminal 2. However, terminal 2 is related to the central heating (which is working) not the hot water.


That wiring is to do with the control of the central heating, so if the heating is working all is well there

The loose wire in 5 is probably the culprit that is associated with the control of the hot water.

You can test it by pressing the button in the centre of the Heat link, so that the 'drip' Hot Water Light symbol is illuminated.

View attachment 180428

If the hot water heats up then, the wiring is OK. During the test the heating will be permanently 'on' also and the Nest thermostat won't operate it. But if you check the pipe from the motorised valve to the hot water cylinder, you will be able to tell pretty quickly if the hot water is flowing from the boiler to heat the hot water cylinder. Be careful not to burn your finger!

 

[Zee Hyde]

Hi Stem

Just re inserted the cables as you suggested a d its working like a charm so your were right it may be loose cable connection to 5.

Thanks again and have a nice day.