Potterton Powermax HE - Remote Programmer (Nest)

[Jamie McDonald]

Evening all,

I took the plunge over the weekend and bought a Nest 3rd Gen Thermostat.

Currently I've got a Honeywell CM707 thermostat connected to my Potterton Powermax HE boiler, using 2 cables to connect to Tr and Tl on the boiler. The Honeywell is programmable so I have the boiler programmer set to 'always on' and the thermostat just calls for heat - easy.

Replacing it as-is is straightforward, however the Nest can control Hot Water as well, and the Powermax has a hot water tank...opportunity strikes...

On the installation wiring diagram for the Powermax, there is a facility for a Remote Programmer, with lines for HWr, HWl, CHr, CHl. The obvious thing to do is connect those up appropriately to the Nest and job done, however the diagram for the remote programmer option suggests the Tr and Tl (Room Thermostat) lines should still be connected to a Thermostat (which in this case would be the Nest).

So, my questions are:
1. Can the Nest be used as a Remote Programmer in this way with this boiler?
2. If so, do I need a Room Thermostat on Tr and Tl or can I leave them disconnected (or looped?)
3. If I need a Room Thermostat, could I connect Tr and CHr, and Tl and CHl to the same points on the Nest?

Apologies for the length of post and numerous questions; I am competent (mostly) but want to be absolutely sure of what I'm doing given the change of configuration.

Thanks,

Jamie

 

[stem]

There's no problem with you using the Nest as a replacement for the Honeywell.

I have just looked at the Powermax manual and you do have remote control terminals for the control of Hot Water & Heating. It seems that you have pretty much figured it our for yourself.

HWl = Hot water live wire (Goes to Nest terminal 5 - Hot water common)
HWr = Hot water return wire (Goes to Nest terminal 6 - Hot water call for heat)

CHl = Central heating live wire (Goes to Nest terminal 2 - Heating common)
CHr = Central heating return wire (Goes to Nest terminal 3 - Heating call for heat)

N2 = Neutral supply to Nest
L2 = Live supply to Nest

You will have to insert a link between terminals TR and TL when the existing thermostat is removed.

 

[Jamie McDonald]

There's no problem with you using the Nest as a replacement for the Honeywell.

I have just looked at the Powermax manual and you do have remote control terminals for the control of Hot Water & Heating. It seems that you have pretty much figured it our for yourself.

HWl = Hot water live wire (Goes to Nest terminal 5 - Hot water common)
HWr = Hot water return wire (Goes to Nest terminal 6 - Hot water call for heat)

CHl = Central heating live wire (Goes to Nest terminal 2 - Heating common)
CHr = Central heating return wire (Goes to Nest terminal 3 - Heating call for heat)

N2 = Neutral supply to Nest
L2 = Live supply to Nest

You will have to insert a link between terminals TR and TL when the existing thermostat is removed.

Thank you very much! Glad I wasn't way off base!

 

[Paul Newcombe Jones]

Hi Jamie

Just a question for you if you don't mind? I have the 3rd Gen Nest with the Powermax He, I've connected as appropriate inc the comments from stem. Not sure if I'm missing something but I was wondering, if the Nest sends a hot water / heating request, do the relevant lights on the boiler light up? Also, do you have the 'on board' program controller set to always on or off? Thanks

 

[stem]

There is a switch to allow you to turn off the internal programmer, and the Nest will control the time as well as the temperature functions. See S9 in the attachment below.

 

[Paul Newcombe Jones]

There is a switch to allow you to turn off the internal programmer, and the Nest will control the time as well as the temperature functions. See S9 in the attachment below.

Perfect, that was all I was missing! Cheers Stem!

 

[Jamie McDonald]

Sorry for the delay in coming back, looks like stem got you sorted. The lights for CH and HW don't light up when the nest calls for them; it just works in the background.

 

[Naz Moideen]

Hi Jamie. I have a potterton powermax he with Nest 2 connected to it. I have bought the gen 3 nest and tried to connect it to the boiler. In the previous set up I had wire from link box in N, L which was looped to 2 and another into 3 which is connected to N, TL & TR respectively on my boiler. HWR and HWL are looped and so is CHR & CHL (pictures are posted).However i wasn't sure regarding connection to control hot water with the new nest. Are you able to post a picture of your nest link box and the connection to boiler please. Thanks.

 

[Jamie McDonald]

Hi Jamie. I have a potterton powermax he with Nest 2 connected to it. I have bought the gen 3 nest and tried to connect it to the boiler. In the previous set up I had wire from link box in N, L which was looped to 2 and another into 3 which is connected to N, TL & TR respectively on my boiler. HWR and HWL are looped and so is CHR & CHL (pictures are posted).However i wasn't sure regarding connection to control hot water with the new nest. Are you able to post a picture of your nest link box and the connection to boiler please. Thanks.

I'm away just now but will check what I've done for you when I get home

 

[stem]

Naz

The photo you have posted is for the Nest Heat Link with Central Heating Control only.

To have control of a Hot Water function you need the Heat Link with the facility for it. It has additional terminals 4, 5 and 6 provided for this purpose.

 

[Naz Moideen]

Hi stem. Thanks for the reply. That photo of the heat link is with nest 2. i have bought nest 3 which has the terminals 4, 5, and 6 and wanted some advice regarding connections.

 

[stem]

Ah OK. In that case, remove the brown link between HWl (Hot Water Live) and HWr (Hot Water Return) at the boiler, then connect them to the Heat Link as follows:

HWl = Nest terminal 5 - (Hot water common)
HWr = Nest terminal 6 - (Hot water call for heat)

That's all you need to do, no other link required at the Heat Link

 

[Naz Moideen]

Hi Stem. I have installed nest 3 and connected as suggested. Central heating is definitely working. I do get hot water but I'm not sure if nest is controlling it. How can i test it. Do i need to switch off the internal programmer using the S9 button? Thanks. Jamie - any possibility of a photo of your setting?

 

[Jamie McDonald]

Hi Stem. I have installed nest 3 and connected as suggested. Central heating is definitely working. I do get hot water but I'm not sure if nest is controlling it. How can i test it. Do i need to switch off the internal programmer using the S9 button? Thanks. Jamie - any possibility of a photo of your setting?

The switch has to be to the left (as you look at it) to hand control off to the nest, and the on-board timer set to off. Couple of pictures included below

In terms of telling whether it's working... If your shower gets cold in a couple of days, it's not! I found (when mine wasn't working as one of the wires had slipped in the terminal) that the hot water tank kept the water hot for 2-3 days all by itself!

 

[Naz Moideen]

Thanks Jamie. In the settings - for the equipment did you choose other boiler with hot water?