Thermostat upgrade connection

[brakke]

Hi,

Whilst doing renovations we removed the old thermostat (old round temperature dial one) and would now like to install a new digital one.
We are hooked up to a communal boiler, which is inaccessible outside the apartment.
Where the main pipe enters the house there is a little electrical Honeywell metallic box connected to a T pipe junction.
The place where the thermostat itself used to be, there are 2 live wires, 1 neutral wire and 1 earth wire coming out of the wall.

The question is whether we can install a digital thermostat here and which wires to connect where so it would work.

Thank you
Bram 

 

[Andy™]

should be possible, but you will probably need one that has volt free contacts that can be used to switch the external boiler supply

 

[brakke]

Hi Andy, 

Thanks for answering my question. But i am still a bit confused as to what to use.

Having done a bit more research, it seems that my thermostat set up, is a 3 wire  set up with 1 live, 1 switched live and 1 neutral.

So I guess I need a thermostat with this set up.

I am not sure how to identify the switched live from the live wire though. Both are red and neither has an indication on it.

Could you let me know how to identify this?

Thank you

Bram

 

[Rob.]

Do you own any test equipment? 

 

[brakke]

Yes I do.

I have just tested the three wires and think I've identified the Live wire.

There was only one wire with 240 V on it. The other red wire didn't have any voltage across it.

Is that assumption correct?

 

[Rob.]

Yes live will be permanently live, switch live will be live when the thermostat contacts have switched over. 

 

[brakke]

So would I be able to connect any thermostat to it?

If i have a 2 wire thermostat, could I just tape off the neutral and connect the Live and Switch Live where needed?

Or will that mess up something else?

Thanks

 

[Rob.]

Should be fine, don't tape up the neutral though. Most will have a spare terminal to connect it to when not necessary. Taping it up is not allowed. 

The neutral is there so that any electronics being used can be powered and to narrow down hysteresis with switching. 

 

[leesparkykent]

Sounds like you have a two port valve on the flow as it enters the property. 

 

[brakke]

Correct. We have a two port mechanical valve controlling the flow.

I presume the thermostat is linked to this valve to operate it?