Nest and vokera syntesi 35

[Michael Long]

Hi folks I'm looking to connect my combi boiler up to nest thermostat,
I have a myson programmable thermostat on the wall at the moment leaving the boiler switch at constantly on.
My question is ,is just a matter of taking power back to the heat link from the boiler and then taking a wire from the thermostat cables on the boiler back to the heat link or is there anything else I need to connect, thanks

 

[stem]

Hi Michael and welcome to the forum. Thanks for the photos. Unfortunately, most that will be able to help you will already be familiar with the Nest Heatlink and the Installation manual, but what we really need to know is the make / model of your existing Myson programmable thermostat, and details of the wires currently connected to it.

 

[Michael Long]

Hi mate thanks for getting back to me.my current thermostat is a myson mprt wired controller,there is only to wires going from boiler to thermostat.

 

[stem]

OK, thanks. Sounds like you have figured it out yourself pretty much. So:

The bottom wire in the photo (brown?) goes to the Heatlink terminal (2) Common

The top wire in the photo (black?) goes to Heatlink terminal (3) heating call for heat.

Then you need to run a 230V N & L supply plus earth to the Heatlink. This should come from the same source as the boiler. Either the 'load' side of the 3A fused connection unit, or the boilers L, N & E terminals that are supplied from the fused connection unit, whichever is easier.

I'm not familiar with the physical construction of your model of boiler, but if it is necessary to open up the room sealed part of the boiler to access the wiring, then the first method should be used. Only a Gas Safe engineer should open up the sealed part.

 

[Michael Long]

After speaking to spark on-site today am going to use a 5 core heat resistant cable and take power from boiler
N boiler-N heat link
L boiler- 3 on heat link (loop 2 to L on heat link)
E boiler - E heat link
T1 to thermostat
T2 to thermostat
The spark did say try it with out the loop first

 

[Michael Long]

You say I take black wire to 3 on the heat link,do I still leave the loop in place, I now count 7 cables including 2 to stat.
Brown to 2
Black to 3
**(L on boiler back to L on heat link)**
N in boiler back to N on heat link
E on boiler back to E on heat link
T1on heat link to stat connections on boiler then on thermostat on wall
T2 on heat link to stat connections on boiler then on to thermostat on wall,
Is this correct mate
Could i take loop 2 to L on heat link

 

[stem]

N boiler-N heat link

OK

Brown to 2

OK

Black to 3

OK

L boiler- 3 on heat link (loop 2 to L on heat link)

No! I didn't mention any link. New Live supply to Heatlink L terminal only.

E boiler - E heat link

OK

T1 to thermostat
T2 to thermostat

OK but should be a separate cable

The spark did say try it with out the loop first

Please forget about any link / loop etc. you don't need it / them. If you had required one, I would have mentioned it previously.

5 wires are required for the mains wiring. Two already exist at the Myson mprt and then the 3 new wires you require are a mains supply N, L & E. So, to summarise the 5 wires as follows:

New 230V supply from the same supply as the boiler to provide power to operate the Heatlink
1) New Live (L)
2) New Neutral (N)
3) New Earth (E)

Thermostat switching wires
4) Brown wire presently going to the Myson mprt is removed from it, and instead goes to the Nest Heatlink terminal (2)

5) Black wire presently going to the Myson mprt is removed from it, and instead goes to the Nest Heatlink terminal (3)

You can use a plug in power supply to power the Nest Thermostat, but if you want to run a wire from the Heatlink to the Thermostat to connect their T1 & T2 terminals, then that's fine, and would be my preferred solution. T1 at the Thermostat goes to T1 at the Heatlink. And T2 at the Thermostat goes to T2 at the Heatlink, However, as this is only 12v, then then a separate cable should be used from the one carrying the mains voltage.

 

[Michael Long]

To summarise
L on boiler to L on heat link
N on boiler to N on heat link
E on boiler to E on heat link
Brown cable that goes to myson thermostat on boiler removed and replaced with new cable an run to 2 on heat link.
Black cable that goes to myson thermostat on boiler removed and replaced with new cable and run to 3 on heat link.
New cable run from T1 and T2 on heat link to T1 an T2 on nest thermostat.
Original cable to myson thermostat will be short as heat link is outside of boiler ,I have easy access at moment

 

[stem]

I think you are about there. Just, not quite sure what you mean by....

Original cable to myson thermostat will be short as heat link is outside of boiler ,I have easy access at moment

However, this is what you should be looking to achieve.



Note, that this is pictorial only to illustrate the connections. In reality, the cable outer sheaths should be extended into the Heatlink and secured under the cable clamps provided.

 

[Michael Long]

Because the cable from myson goes to the
Boiler but heat link is 30 cm away from the boiler.

 

[stem]

Then you will need to shorten the existing cable somewhat. [I am assuming here that the Myson thermostat is not positioned close to the boiler] Or, if it is buried in the wall, remove it completely and install a new cable in its place.

 

[Michael Long]

Running a new cable from the heat link to nest thermostat is going to be no bother mate.
Just like to thank you for patients,
Means alot to get a helping hand

 

[Michael Long]

I know this is not a conventional question,
Since I'm not keen in having my heat link in the same place as my boiler.
Would it be ok to take power from another source say plugging it in to socket wit a 3 amp fuse.

 

[stem]

It's good practice to have the same isolator for the entire heating system, that way if you have a problem with the boiler the engineer switches off the isolator and everything is off, there's no risk of him getting a surprise from another part of the system.

so I wouldn't have two separate supplies, and I wouldn't recommend it, but would work. Also, fixed appliances such as the Heatlink should be wired via a fused connection unit anyway. Plugs and sockets are for portable appliances.

 

[Michael Long]

Just a follow up question . Insulation of nest went smoothly ,but I'm wondering if i should disconnect the mechanical timer on boiler
Ive been getting fault code 01 quite regular and wondering if this could be the cause.
Ive had British gas engineers out but thee don't seems to be able to fix problem