Nest Install Logic Combi Boiler

[gbiddy]

Hoping someone can offer some advice on a Nest install for a Logic + Combi boiler. I'm not against getting someone out to install if necessary but wanted to check if I could do it myself if it's fairly straightforward.

I've got a stand for the Nest so no need to cable it back to the heat link. It's replacing a Siemens Wireless stat, which is setup as below:

2017-11-30 19.41.41

• gbiddy
• 4 Dec 2017

2017-11-30 20.46.30

• gbiddy
• 4 Dec 2017

I'm hoping it's just a case of re-using the current wiring and doing the following:

Siemens -> Nest

N = N
L = L
LX = 2
L1 = 3

Any help / advice is much appreciated.

Cheers.

 

[jackthom]

Yes it’s a very straightforward replacement with the heatlink connections as you have listed.

 

[muggles]

Put your boiler case back on - it forms the safety room seal for the boiler and should only be removed and refitted by a Gas Safe Registered Engineer, who can then carry out the necessary checks to ensure that the seals are not compromised and the boiler is operating safely

 

[ericmark]

Page 32 on this document shows the connections for the OpenTherm right hand picture which will connect to OT1 and OT2 on nest, I think you will likely need to replace the link shown for room thermostat in left hand picture.

All I have done is hunt internet for both wiring diagrams, I have simply read them. I have never fitted Nest but looking at the Siemens picture it would seem that thermostat is not OpenTherm so really not suitable for your boiler, the Nest would seem a far better selection.

If I am correct, then it does not make me really want to trust Corgi or Gas Safe when they clearly fitted wrong thermostat, however in every trade we have people who are good and people who are bad, but clearly a boiler manufacturer worth their salt would not require a Gas Safe and a Part P tradesman to be on site at the same time, so electrical connections should be able to me made without affecting the gas part of the boiler. Unless of course the manufacturer is really stupid.

 

[muggles]

Page 32 on this document clearly a boiler manufacturer worth their salt would not require a Gas Safe and a Part P tradesman to be on site at the same time, so electrical connections should be able to me made without affecting the gas part of the boiler. Unless of course the manufacturer is really stupid.

They don't require a Part P installer, that much is true, as boilers are supplied via an FCU and anything after the FCU including all controls can be wired up by a Gas Safe Registered Engineer. Any boiler installer worth their salt can wire up controls.

Ideal, Intergas, Baxi, Worcester, Vaillant, Viessmann, and Ravenheat all need the safety room sealing cover to be removed in order to access the electrics, and so should only be wired up by a Gas Safe Registered Engineer.

=====================================================
Correct, this is a GSR stipulation, and the forum policy. See the Sticky post on Gas Work.
"The outer cover of many boilers now encloses the combustion airflow and is the Room Seal for the boiler. Its removal, even if only to access boiler wiring, therefore requires a GSR Engineer."
Mod

 

[gbiddy]

Thanks for the replies everyone. Good to know RE: the outer cover, I guess I probably should have known better, but my enthusiasm to get a better understanding of how everything was connected up got the better of me. Having said that, all of the covers have been replaced as I found them, do I now need to have these checked?
Can't really comment on the suitability of the current thermostat (or who fitted it) because it was done prior to us owning the house. We have had the boiler serviced in the last 12 months though and no concerns were raised.

Cheers.