Potterton Powermax HE - Remote Programmer (Nest)

[Oz Austin]

The problem was the older Drayton Unit. I managed to get hold of another Drayton Unit and it worked fine, but putting the original unit back on it popped a fuse again. that's why, after doing hundreds of other projects, i was confident to come back to this job.

Anyway, I have wired up the Heat Sink and that powered fine. I then plugged in the nest thermostat into a phone charger and it connected to the heat sink fine. the nest is now controlling the boiler as far as i can tell. When i demand heat from the rads via the nest the boiler clicks into action and the rads get hot. it also does the same to the hot water but will finally be convinced when i still get hot water in a couple days. (funny thing though, when i put the S9 switch to the left off position the control panel on the boiler still stays on as if its working on its own, unlike other descriptions of it not illuminating, doesn't bother me as the nest and boiler are chatting to each other and working)

the only issue is not knowing how to connect the nest thermostat to the old wiring. As Muggles said above I connect the brown and brown sleeved wires at the wall to the header unit and then I do believe i have to remove 2 wires from the boiler and extend them and connect them to the T1 and T2 ports in the heat sink. please can you let me know which 2 wires from the picture they are? I don't have a meter and the £100 call out fee just to get the electrician to point to the wires for me to adjust. (this image was taken from an earlier post that i copied and works as i have written above).

 

[stem]

I'm not sure you understand the concept. The Nest Thermostat does not connect to the boiler. The Nest thermostat communicates wirelessly with the Heat link, but it needs 12v to power it. There are two ways of doing this, you can get the 12v power from a plug in power supply which is what you have said you have done already.

Or, alternatively you can get the 12v power from the Heat link.

To do this it requires a cable between the Heat link and Nest thermostat such that:

T1 at the Nest thermostat is connected to T1 at the Heat link, and
T2 at the Nest thermostat is connected to T2 at the Heat link.

The Nest thermostat is not connected to the boiler.

 

[Oz Austin]

yea i was just out running and i find running clears my head and i get some good thinking time, i thought that might be the case. so its a matter of finding where those cables that were connected to the old Drayton are plugged into and connect them to the T1 and T2 sockets in the heat link. That then will create the 12v loop from the sink and the head unit.

so does the drayton connect to the boiler via hard wire as its on a 240v and it blows fuses in the boiler if activated (yep its faulty, the Drayton that is) as i cant imagine thats wireless, its older than i am.......if so then which 2 wires so i can disconnect them from the boiler and connect them to the heat sink...

 

[stem]

so does the drayton connect to the boiler as its on a 240v and i cant imagine thats wireless, its older than i am.......

That all depends upon the type of heating system that you have. If you have a system with motorised valve(s) then the external controls will operate them, and the motorised valve(s) will be wired to the boiler. If it's a combi boiler then the Drayton 'device' may be wired directly to it.

I have wired up the Heat Sink and that powered fine. I then plugged in the nest thermostat into a phone charger and it connected to the heat sink fine. the nest is now controlling the boiler as far as i can tell. When i demand heat from the rads via the nest the boiler clicks into action and the rads get hot.

If the Nest's up and running as you say, you will have figured this out and resolved it already.

 

[Oz Austin]

Stem,

1st point, I have the Potterton Powermax HE 115

2nd point, yes its all working fine, but i have to have the nest sat on the side powered by a USB phone charger. I want it where the old drayton thermostat was, on the wall.

by the sounds of it i will have to remove the drayton completely, isolate the cables safely, fill the hole and paint it over and then go and buy a stand for the nest to sit on a table somewhere. Doesn't make sense to me, surely those wires that i need from the Drayton are connected to the boiler somewhere and i just need to disconnect them there and attach them to the heat sink....to me that sounds simple or am i missing something here?

 

[Gorners]

I fitted my brothers Potterton 155x to Nest and did exactly what you said. The thermostat wires came into the airing cupboard next to the boiler, I simply disconnected these from the boiler and put them into the 12v supply in the heat link. There was an extra earth wire which I just isolated.

 

[stem]

1st point, I have the Potterton Powermax HE 115

In that case the thermostat can go to boiler, as per the diagram below.

Except in your case, you don't have a 'room stat' connected to the room stat terminals, and the terminals Tr and Tl are bridged with a wire link.

2nd point, yes its all working fine, but i have to have the nest sat on the side powered by a USB phone charger. I want it where the old drayton thermostat was, on the wall.

In that case, as you want to use the old thermostat cable you will have to trace it back to it's origin, and find out where it is presently connected. There could be several possibilities. When you find the origin, if you need any help decommissioning the old room stat, post back a photo of the wires at the thermostat end and the wires at their origin.

 

[Oz Austin]

Stem,

thanks for the above, fully understand. Muggles told me what wires to connect the the Nest header unit i just need to find the other end and connect them to the T1/T2 terminals, but have no idea how to trace them back.....uuugh DIY is hard....

 

[Oz Austin]

OK i think i just had a light bulb moment....

That picture that i posted above was taken after i wired the Heat Link to the boiler. I removed 2 wires from the room stat (Tr and Tl) and secured them away. I then put that link in between them as i was copying a pic from earlier in the post......

Now are those 2 cables that i removed from Tr and Tl the cables im looking for? If so how do i test them before plugging them into the heat link and the Nest header Unit???

 

[stem]

YES! The wires would have been in those terminals

I would test the wires with a multimeter, by:

1. Checking that they aren't live.

2. Joining them together at one end, and taking a resistance reading at the other end, I would be looking for a low value for example 0 to 1 ohms.

3. Then disconnect them, and remeasure the resistance. Now it should be a high reading (infinity)

 

[Oz Austin]

Is there a way for me to test them?

Also looking at this pic of my Drayton header unit which 2 wires do i connect?

On the boiler i disconnected a grey and black wire, so on the drayton i will assume i connect the N and the 3 wire as they are the same colour.

apologies about all these questions, i had a big scare the first time i tried to connect this all up about blowing the boiler and the Nest, I got lucky and only blew a fuse. This time im getting somewhere, just want to finish the job correctly.

The pictures attached shows the boiler end before i connected the Heat Sink. You can just about see the cables at the bottom connected to the Tr and Tl terminals. The other picture is of the Drayton still connected but not working (as i found out later that was another victim of my tomfoolery the very first time i tried).

 

[stem]

I'm guessing that you wrote...

Is there a way for me to test them?

...before I wrote:

I would test the wires with a multimeter, by:

1. Checking that they aren't live.

2. Joining them together at one end, and taking a resistance reading at the other end, I would be looking for a low value for example 0 to 1 ohms.

3. Then disconnect them, and remeasure the resistance. Now it should be a high reading (infinity)

Regarding the old room thermostat.

L is Live
N is Neutral
3 is switched live

This thermostat has an accelerator heater, hence the neutral connection. All of the wires in the cable should be disconnected at both ends before using it to connect to T1 & T2

 

[Oz Austin]

OK, to me that sort of doesnt make sense, if the wires i removed from the boiler Tr/Tl terminals are the same wires connected to the drayton on the wall (grey and black) that would mean im connecting a Neutral and Switched Live to the Nest????

OK when i look at that pic of the boiler all 4 of those wires match whats in the drayton.

Drayton Wall end..............................Boiler End
Earth = Yellow/Green
L = Brown.......................................L = Brown
3 = Black........................................Tr = Black
N = Grey.........................................Tl = Grey

So im assuming that i:
Disconnect the black from the boiler and put it into T1 on Heat Sink
Disconnect the Brown from the boiler and put it into T1 on Heat Sink
Connect Black from Drayton into T1 on Nest Header
Connect Brown from Drayton into T2 on Nest Header

 

[muggles]

OK, to me that sort of doesnt make sense, if the wires i removed from the boiler Tr/Tl terminals are the same wires connected to the drayton on the wall (grey and black) that would mean im connecting a Neutral and Switched Live to the Nest????

No.

One end of those wires should be connected to the Nest Heat Link T1 & T2 terminals, and nothing else.

The other end should bre connected to the round Nest base plate T1 & T2 terminals, and nothing else.

Thus the Heat Link is connected to the Nest and provides power for it.

 

[Oz Austin]

@muggles yes understand that....im just trying to make sure i have the correct wires. I dont want to go back to where i was a few weeks ago.

I also understand that i could get an engineer in to do this but i dont have the spare £100 call out fee...you guys on here are being a really big help and have got me this far also with me doing extensive research am starting to understand electrics....lol will be an electrician soon and will charge other people £100 call out fees lol