Replacing Salus wireless thermostat with Nest

[MugabesDeadCat]

We have a Nest 3rd generation thermostat waiting to be installed and I was considering having a go installing it myself but just want to ask opinion on here first then decide whether or not to get a professional to do it.

There is a fused spur going into the Salus which then goes onto the boiler shown below.

Will all these cables fit into the Nest? And which slots do the COM & NO wires go into on the Nest?

 

[stem]

You make no mention of using the hot water control section of the Heatlink, so I am assuming that you have a combi boiler that delivers hot water 'on demand' when a tap is opened, and you will only be controlling the central heating with the Nest

The Nest Heatlink would connect as follows:

Grey wire in Salus NO = Nest Heatlink (3) Heating Call for heat

Back wire in Salus COM = Nest Heatlink (2) Heating Common

2 x Brown wires in Salus L = Nest Heatlink (L)

2 x Blue wires in Salus N = Nest Heatlink (N)

Earth wires in the Heatlink earth terminal

The Nest thermostat itself can be powered using a separate plug in power supply, or by connecting T1 at the Heatlink to T1 at the thermostat and connecting T2 at the Heatlink to T2 at the thermostat.

 

[MugabesDeadCat]

Sorry, yes, it's a Worcester combi boiler.

I'll use the plug for powering the thermostat.

Sounds pretty straight forward then.

Thanks

 

[MugabesDeadCat]

So I have to take the red connector off the earth wires and place them into the heatlink?

 

[stem]

Yes you are fortunate yours is one of the easiest I've seen.

You can get two wires into the Heatlink terminals, but be careful that there aren't any copper whiskers poking out as the terminals are quite close together. Secure the cable sheaths (ie not just the wires) under the clamps provided at the base of the Heatlink.

 

[stem]

So I have to take the red connector off the earth wires and place them into the heatlink?

Yes, you should really unless the Heatlink instructions specifically state that it is "double insulated" and so doesn't need an earth connection, but I always put them in the earth Heatlink terminal.

If it is double insulated, [The symbol for this will be a box inside another box] then you can leave them as they are in the crimped connector.

 

[MugabesDeadCat]

Man there's not much space in there!!

Here goes nothing!

 

[MugabesDeadCat]

With regards to positioning of the thermostat. We have TRV's in ever room except the bathroom and kitchen. We used to have the Salus in the kitchen.

Would it be ok placing it in there? It's more a kitchen diner than an out and out kitchen. It's the most used room in the house. Or would the living room be better? But I'm wondering if it'll work against the TRV's in there. Or do you just set them to max?

 

[stem]

The room thermostat will switch off all of the radiators in the house when the set temperature is reached in the room in which it is located. Therefore, it should be in the last room to get warm. Understand this concept and you will be able to work out the best location for your home.

Because properties are different in use, orientation, construction size etc., it's not possible to say your thermostat should be located here or there. But consider the following.

Do not locate the thermostat in a room where it will be subject to other heat sources such as cooking appliances, used fireplaces, or sunlight. Any extra heat that warms up the room where the thermostat is located, will switch off the thermostat, and all of the radiators in the rest of the property.

It should be located in an open space to allow air to circulate freely around it so that it senses the true ambient temperature of the room in which it is located, not stuck in a corner, behind curtains or furniture, or subject to drafts.

Do not fit a TRV to the radiator in the room where the thermostat is located. if you do, it could turn off the radiator before the temperature set on the room thermostat is reached. In this event, the room thermostat will never turn off, and so there is no point in having it. [Some will fit a TRV, and either remove the sensor head or leave it set on maximum, but at some point no doubt someone would turn it down, so personally I would not fit one in the first place]

Fit TRV's to all other radiators to prevent the other rooms overheating

Ideally it should be in a place that is the last room to warm up, so that the radiators remain 'on' in all of the other rooms first to allow them to heat up before the main thermostat starts turning the whole system off. You may have to downsize the radiator in the room where it is located to achieve this.

 

[Simon p]

You make no mention of using the hot water control section of the Heatlink, so I am assuming that you have a combi boiler that delivers hot water 'on demand' when a tap is opened, and you will only be controlling the central heating with the Nest

The Nest Heatlink would connect as follows:

Grey wire in Salus NO = Nest Heatlink (3) Heating Call for heat

Back wire in Salus COM = Nest Heatlink (2) Heating Common

2 x Brown wires in Salus L = Nest Heatlink (L)

2 x Blue wires in Salus N = Nest Heatlink (N)

Earth wires in the Heatlink earth terminal

The Nest thermostat itself can be powered using a separate plug in power supply, or by connecting T1 at the Heatlink to T1 at the thermostat and connecting T2 at the Heatlink to T2 at the thermostat.

In my salus transmitter I only have one of each colour and no earth wire. Is it okay to follow these instrutions

 

[stem]

Probably, but it depends. You need to say what model of Salus you have (I'm a bit puzzled by your use of the term "transmitter" with wireless thermostats there is usually a thermostat and receiver) say what terminals the wires are in, and if there are any links made between them, or even better post a photo.

You can't take too much notice of the wire colours, they would have been chosen by the original installer. It is what is connected to the end of each wire that determines what it does, not the colour of its insulation.

 

[Simon p]

Salus reciever

• Simon p
• 23 Nov 2020

The colour of the wires directly correspond to the terminal markings that you mentioned ie grey wire in salus no, black in salus com etc. The only discrepancy was that I only had 1 of each colour and no earth

 

[stem]

In that case, if you have 4 wires, one in each terminal and no additional links present, then yes they will transfer the same.

1. Wire in Salus NO = Nest Heatlink (3) Heating 'Call for heat'

2. Wire in COM = Nest Heatlink (2) 'Heating Common'

3. Wire in L = Nest Heatlink (L)

4. Wire in N = Nest Heatlink (N)

The Salus doesn't need an earth connection, but the Nest Heat link does have an earth terminal. However, the instructions only state that it should be connected if terminals T1 and T2 are used to power the Nest thermostat.

So, if you intend to connect the thermostat to T1 & T2 you will need to add an earth connection to the Heat link. If you plan on using a separate plug in power supply for the thermostat it would appear you don't.

 

[ianmcd]

if you intend to connect the thermostat to T1 & T2 you will need to add an earth connection to the Heat link

@stem as always you are totally correct, but I have always wondered why you need to wire in an earth when using the 12 power supply, have you any idea ?

 

[Simon p]

Thanks a lot for your advise, I will be using the USB cable to power the thermostat.