NEST install - wiring advice

NEST install - wiring advice

Author
Discussion

Otispunkmeyer

Original Poster:

12,557 posts

154 months

Sunday 22nd February 2015
quotequote all
Ok so I am wiring my NEST in this weekend and I think I have it sorted.

The boiler already has a Wireless RF receiver on the front which controls the call for heat. The Module, as far as I can figure, is sent 240 V live and neutral from a header on the main board. It sends back a constant 240 V to the hot water pin and when I ask for heat, I can hear a relay and when that happens 240 V is also sent to the central heating pin.

So my plan is thus>

The NEST heat link is already powered via a normal plug socket with Live and Neutral.

I plan to take the 240 V from the header (that would have powered the RF module) out of the boiler to pin 2 on the heat link. Then take pin 3 on the heat link back to the boiler where it will connect to the central heating pin. I will then jumper the 240 V from the header to the hot water pin, maintaining its constant 240 V as it is now.


This way, the NEST heat link is powered separately from the boiler and is then switching the boilers own 240 V supply for the call for heat. I think this way is best incase I need to trouble shoot anything. In this case, if the boiler is switched off at the mains, then the whilst the heat link will remain powered, it will not have any mains voltage to switch because that is from the boiler. The only issue here would be having 240 V travelling on the two wires within the same flex. Is that ok?

I could however, wire the 240 V from the boiler PCB header, to the heat link, daisy chain the live to the heat link pin 2 then send a single live line back to the boiler for the heating pin and again jumper the live and hot water pins to maintain 240 V. But that way, if the boiler is off at the mains, so is the heat link.

which is best, or are they both legit?

moles

1,794 posts

243 months

Sunday 22nd February 2015
quotequote all
What boiler you got?.

Otispunkmeyer

Original Poster:

12,557 posts

154 months

Sunday 22nd February 2015
quotequote all
moles said:
What boiler you got?.
Remeha Avanta Plus 39C

It does have a second header but this, I have since found out, is for OpenTherm control, not volt-free switching. Nest does not have OpenTherm abilities. I tried the volt-free switching setup yesterday and the boiler does not function correctly.

At the moment, the boiler is controlled by the Wireless module by switching live to call for heat. I am just going to replace this arrangement. But I was just undecided about how I should be powering the NEST heat link, i.e. via the boiler or via its own wall socket, but in both cases switching the live that is coming from the boiler. Not switching an external live which could therefore still be live even if the boiler is off at the switch.


dirkgently

2,160 posts

230 months

Sunday 22nd February 2015
quotequote all
you should power all controls from the boiler X2 4&5 and 240v heating demand X2 1.

Otispunkmeyer

Original Poster:

12,557 posts

154 months

Sunday 22nd February 2015
quotequote all
dirkgently said:
you should power all controls from the boiler X2 4&5 and 240v heating demand X2 1.
Yep, just spoke to my dad, he recommends the same. 4&5 to heat link for power. Daisy the live over to pin 2. Then single live off pin 3 back to boiler on pin 1 on X2, then jumper across 4&3 for the hot water which has constant live as there is no separate hot water timer/controller, it's controlled off a hall effect.

Otispunkmeyer

Original Poster:

12,557 posts

154 months

Sunday 22nd February 2015
quotequote all
So I got it working...

For a while


Now I have an error which corresponds to no through flow. Pump not spinning. As far as I can tell its not being fed 240 V, but not sure if that means relay has died or something controlling the relay, or if the motor has gone whether it would still be fed 240 V.

This will be expensive! Lol

The boiler is in poor state though, most of the components inside have already been replaced. So there is still an outside chance this is coincidence. Occam might argue otherwise though!

dirkgently

2,160 posts

230 months

Sunday 22nd February 2015
quotequote all
do you have 240v on X4 2?

Sheepshanks

32,531 posts

118 months

Sunday 22nd February 2015
quotequote all
Otispunkmeyer said:
I tried the volt-free switching setup yesterday and the boiler does not function correctly.
Wonder why that didn't work. Did you put the link back afterwards?

Otispunkmeyer

Original Poster:

12,557 posts

154 months

Sunday 22nd February 2015
quotequote all
All OK folks. Wiring all correct, plumber came round to sort the pump and checked my wiring. Something tripped the pump though. A quick twist of the motor with a screwdriver and, most importantly, a press of the reset button and all is fine and has been since 4:30pm. Fingers crossed.

More it probably just needed a reset, but I presumed turning it all off and in again would clear errors. But you have to hit the 'R' button to clear. Will keep an eye on it, but so far it's all working.

Otispunkmeyer

Original Poster:

12,557 posts

154 months

Sunday 22nd February 2015
quotequote all
Sheepshanks said:
Wonder why that didn't work. Did you put the link back afterwards?
Took the jumper off but had no idea which of 7 and 8 (on X9) was common and which was call for heat or if it even mattered with volt free switch. I am assuming it doesn't because the boiler behaved the same with wires in either way. It just came on and then ran continuously with calls for heat having no bearing on boiler operation.

I may have also had to disconnect the live switching parts as well, ( ie couldn't keep the original controller as well) but I've just gone the live switching route now and it works so I am not touching it any more!

981C

1,091 posts

147 months

Saturday 3rd October 2015
quotequote all
Hi Folks

Maybe you whizzkids can help me, too?

I'm trying to install the nest Thermostat on Zone 1 (see below). It's a 2nd Generation and I'm really struggling:





I've connected the 240V supply to the first two terminals on the Heat Link and bridged the live(L) across to the common (2), but I'm at a loss as to how to connect the 'Call-for-heat' as well as the red Zone 1 cable coming from the programmer. The manual states that the programmer should be left as is and always on and the 'Call-for-heat' wire connected to the control box. Now I assume that because I will now be calling for heat via the programmer all the time that I need to have the Heat Link in the circuit to act as the new switch.

Not sure how to achieve this as I'm confused as to how the current set up activates the motorised valve (Honeywell V4043H) and the boiler from a single signal via the red Zone 1 wire.

Thanks!

Edited by 981C on Saturday 3rd October 22:00

stanwan

1,890 posts

225 months

Saturday 3rd October 2015
quotequote all
981C said:
Hi Folks

Maybe you whizzkids can help me, too?

I'm trying to install the nest Thermostat on Zone 1 (see below). It's a 2nd Generation and I'm really struggling:





I've connected the 240V supply to the first two terminals on the Heat Link and bridged the live(L) across to the common (2), but I'm at a loss as to how to connect the 'Call-for-heat' as well as the red Zone 1 cable coming from the programmer. The manual states that the programmer should be left as is and always on and the 'Call-for-heat' wire connected to the control box. Now I assume that because I will now be calling for heat via the programmer all the time that I need to have the Heat Link in the circuit to act as the new switch.

Not sure how to achieve this as I'm confused as to how the current set up activates the motorised valve (Honeywell V4043H) and the boiler from a single signal via the red Zone 1 wire.

Thanks!

Edited by 981C on Saturday 3rd October 22:00
Where's your old wall thermostat location? I would place the heat link in that location and have your programmer power it constantly. Trust me, It'll be easier!!!


981C

1,091 posts

147 months

Saturday 3rd October 2015
quotequote all
stanwan said:
Where's your old wall thermostat location? I would place the heat link in that location and have your programmer power it constantly. Trust me, It'll be easier!!!
Hi

That was my plan, unfortunately it's just a little too far from the thermostat to be in range :-(

How would I wire it there anyway? surely I'm still dealing with the same cable set up?

Rickyy

6,618 posts

218 months

Sunday 4th October 2015
quotequote all
Your red wire (from zone 1 of the programmer) needs to connect to "common", then you need to identify which zone valve is for zone one and connect "call for heat" to the brown wire of that valve.


981C

1,091 posts

147 months

Sunday 4th October 2015
quotequote all
Rickyy said:
Your red wire (from zone 1 of the programmer) needs to connect to "common", then you need to identify which zone valve is for zone one and connect "call for heat" to the brown wire of that valve.
Thanks Rickyy

I worked it out late last night - exactly as you said. Works a treat. Only minor issue is that my programmer can't be set to always on, so I may have to remove that loop from it in the future.

FYI for any future readers, I had wired it correctly at the outset but the Heat Link needed to be reset. By default it seems to be 'on'.