Replacing heating timer.

[martyuk]

Hello everyone, I am after a little help.

I am looking to replace my timer for my heating which is a Landis & Staefa RWB7. I have bought a THR870 homexpert and just took the old one off the wall. I noticed there is a L and N and then 2 black wires on terminal 2 and 4. Here is a picture.

I have tested the 2nd and 4th wire and only 4th is live. I am a little confused on how to wire up my new thermostat. Any help would be greatly appriciated.

Marty

 

[TCCHeating]

Are you sure t4 is live? On that programmer i would expect t2 to be live.

When the programmer is turned on it makes a connection between t2 to t4 making t4 live as well.

Perhaps it was wired wrong in the firstplace. It obviously still worked on the old programmer, but imo those black wires are the wrong way around

 

[martyuk]

Are you sure t4 is live? On that programmer i would expect t2 to be live. When the programmer is turned on it makes a connection between t2 to t4 making them both live.

Perhaps it was wired wrong in the firstplace. It obviously still worked on the old programmer, but imo those black wires are the wrong way around

Ps. Where is the live coming from? Normally there is a link between L and t2.

Thanks for the reply mate. Yes T4 is live. I found this online http://w3.siemens.co.uk/buildingtec...l-controls/documentation/Documents/rwb7_i.pdf and looks like it might have been wired up wrong.

I have just traced the wires back to my boiler and about to take the front off to see where they are coming from.

 

[TCCHeating]

Yep theyre definately the wrong way around. When you install the new programmer put them in the correct terminals. I am guessing you dont have a room stat? (Unless they have connected that at the boiler)

So at the moment the wire in t4 is the live supply from the boiler. The wire in t2 is the live return to the boiler.

 

[martyuk]

Yep theyre definately the wrong way around. When you install the new programmer put them in the correct terminals. I am guessing you dont have a room stat?

So at the moment the wire in t4 is the live supply from the boiler. The wire in t2 is the live return to the boiler.

No I don't have a room stat. thats why I am getting the new unit. You have just made me think. Will this new unit pick up room temp or will I need a room stat aswell?

I have traced the wiring back and yes its connected at the boiler. Here are some more pictures from the boiler end.

If they are the wrong way around. How do I wire them into the new unit? there is 8 diagrams and even though I feel compitent to replace electricals, this has my head spinning haha.

 

[TCCHeating]

Sorry, didnt read your first post properly. You are replacing a programmer with a programmable room thermostat. That is fine. As long as your old programmer is in a suitable place for a thermostat (most arent)

Wireing is simple. Just connect the black wires to a and b on the new honeywell stat. A is live supply and b is live return. there is no need for the perm live and neutral that your current programmer has.

 

[martyuk]

Thank you so much!

You mentioned the placing of the thermostat. It is currently placed in the kitchen. Is this location ok? If not i can drill throught the wall and it would be situation in my living room.

 

[TCCHeating]

Thank you so much!

You mentioned the placing of the thermostat. It is currently placed in the kitchen. Is this location ok? If not i can drill throught the wall and it would be situation in my living room.

No. Kitchen is normally a bad place as there are other sources of heat. Eg the cooker.

Living room is much better. But may also have other sources of heat. Eg fire???

If you have trvs installed on the rads, make sure they are open fully on the rads in the room you install the new thermostat. Or even better remove the heads from them.

 

[martyuk]

Once again thanks for your help. I have now relocated the thermostat into the living room after looking at alot of guides on the best place for it to be. The wife doesn't seem to happy about me having to chase the wiring but it was her idea to change the thermostat haha.

Thanks