Replacing 3 wired thermostat with 2 wired digital thermostat

[Hedgerow]

A 3 wired thermostat is being replaced with a 2 wired digital thermostat powered by batteries. Is it necessary to know how the 3 wired thermostat is connected to the boiler before replacing the thermostat? I have attached images of the 3 wired thermostat and its wiring diagram.

 

[Sintra]

If it’s a 2 wire stat then just use red and yellow and put a connector block or wago on the blue.

 

[Hedgerow]

If it’s a 2 wire stat then just use red and yellow and put a connector block or wago on the blue.

Thanks for your help.

 

[tony clark]

agree with the above

 

[Deleted account]

Are you going from 3 wire 230v to 2 wire 12v?

I think I’d rather disconnect blue at each end.

 

[Sintra]

Are you going from 3 wire 230v to 2 wire 12v?

I think I’d rather disconnect blue at each end.

If he is then the connection at the boiler will be wrong

 

[Hedgerow]

Are you going from 3 wire 230v to 2 wire 12v?

I think I’d rather disconnect blue at each end.

The instructions with the digital thermostat say "If there are only two wires they are the control wires -if there are more than two wires, identify the two control wires. They are usually black or grey.
Note: If there are more than two wires, the others are power supply wires and are useless here. They are usually brown, blue, green or yellow. "

 

[Deleted account]

In answer to your first question. Yes I would like to know how it is connected to the boiler. And I would like to see installation instructions for new thermostat.

Some boilers do not have a permanent live and work off a switched live and neutral only.

There are lots of ways to wire in a boiler.

 

[Hedgerow]

In answer to your first question. Yes I would like to know how it is connected to the boiler. And I would like to see installation instructions for new thermostat.

Some boilers do not have a permanent live and work off a switched live and neutral only.

There are lots of ways to wire in a boiler.

Thanks. The installation instructions for the digital thermostat are as my previous post, there are no instructions for the boiler. It would appear to be a matter of isolating the control wires from the old thermostat and using them in the 2 wired thermostat.

 

[Deleted account]

Without knowing all the facts I would not proceed. I would want to see the actual wiring in the boiler to get the full picture before doing anything with stat.

I would not ask anyone to remove the cover of a boiler to get access to wiring unless they know what they are doing.

It may be a case of blanking of the blue as has been said, but would want to prove this with testing and inspection prior to installation.

 

[Hedgerow]

Without knowing all the facts I would not proceed. I would want to see the actual wiring in the boiler to get the full picture before doing anything with stat.

I would not ask anyone to remove the cover of a boiler to get access to wiring unless they know what they are doing.

It may be a case of blanking of the blue as has been said, but would want to prove this with testing and inspection prior to installation.

Ok. Thanks again.

 

[EricMark]

In this case put the N safely in a connector and just use other two connectors.

I would agree that having just two wires to the thermostat does not mean it works on 230, or 24 volt it could be a variable voltage connected to the OpenTherm terminals with some thing like the Nest e, but that is not the case here.

 

[Hedgerow]

In this case put the N safely in a connector and just use other two connectors.

I would agree that having just two wires to the thermostat does not mean it works on 230, or 24 volt it could be a variable voltage connected to the OpenTherm terminals with some thing like the Nest e, but that is not the case here.

It's actually a Netatmo digital thermostat- 2 wires.

 

[EricMark]

It's actually a Netatmo digital thermostat- 2 wires.

So digital means it turns off/on, and analogue means it turns up/down? Or does digital refer to the display and have nothing to do with the thermostat?

 

[Hedgerow]

So digital means it turns off/on, and analogue means it turns up/down? Or does digital refer to the display and have nothing to do with the thermostat?

Netatmo don't use the word digital, that's me for the display. Netatmo call it a smart thermostat because it can be used via wi-fi or hardwired.