Wireless Thermostat and TRVs

[Retain81]

Hello all,

I've been doing a lot of reading lately around installing wireless thermostats and am about to take the plunge and order a Honeywell CM927. Fitting seems straightforward but, if I'm out of my depth once I've looked at the wiring on my existing Siemens RWB7, I'll get a sparky in

My question is actually around the compatibility of room thermostats with TRVs. I don't have a thermostat at the moment but have TRVs on ALL radiators. I've read in a lot of places that wherever I put the thermostat receiver (likely to be the lounge), I shouldn't have a TRV on that radiator. Given that I may want to move the thermostat around... it is wireless after all... I was wondering if setting the TRV to max on that radiator would be sufficient rather than replacing with a normal valve?

Don't get me wrong, I wouldn't be moving it all the time but there's the odd day (if I'm working from home for instance), where I may want one of the upstairs rooms to control the temp as I'm mainly there rather than the main living space of the house.

Thanks in advance - central heating n00b as you can tell!

 

[D_Hailsham]

I've read in a lot of places that wherever I put the thermostat receiver (likely to be the lounge), I shouldn't have a TRV on that radiator.

It's not the location of the receiver that's important but the control unit. The receiver is hard wired.

Given that I may want to move the thermostat around... it is wireless after all... I was wondering if setting the TRV to max on that radiator would be sufficient rather than replacing with a normal valve?

Setting the TRV to max will be sufficient.

 

[Whitespirit66]

Best to leave the TRV set to max in the room where the stat will be, otherwise they will work against each other.

Wiring in the new CM927 is really easy, if you have done any wiring. Otherwise, yes leave to a heating engineer, not an electrician. Sparks have their uses but ch ain't one of them.

 

[Retain81]

Thanks all - that clears it up about the TRV then (and yes, sorry - I meant the control unit i.e. the portable bit!).

Regarding the installation then... I would class myself as 'novice' when it comes to wiring. DIY in general I'm fine with (as in I can build things and they tend not to fall down), but wiring experience is limited. I've never, nor would ever consider, installing new wiring but have replaced things like broken plug sockets, outside lights and standard light switches for dimmer switches. That's all nice and easy because all I had to do was note down the existing wiring and replace like for like!

Reading the installation guide for the Honeywell and also my existing timer, it starts to say things like "if 240v mains switching is required then install link wire to terminal x', etc... no idea what that means!! Is that one of those things that would be self evident when I take the panel off my existing timer?

If it helps, the combi-boiler is a Worcester 24i. It must be an old one as a) the product literature on the website looks nothing like mine and b) it's in that attractive beige colour that you just don't see nowadays

 

[D_Hailsham]

Do you have a wall thermostat as well as the RWB7?

 

[Retain81]

Do you have a wall thermostat as well as the RWB7?

Nope - just the RWB7.

Crude diagramatic!

Main fuse box ------> isolator switch

isolator switch three returns:

------> fuse ------> burglar alarm (I think!)
------> RWB7I
------> boiler

And then RWB7 ------> boiler (separate cable - direct link between the two).

Does that make sense? I can post piccies in a while once I've picked the little one up from nursery if it helps?

Thanks again for your help (great forum.... why have I not used this before!).

 

[D_Hailsham]

Do you have a wall thermostat as well as the RWB7?

Nope - just the RWB7.

Can the Receiver go in the same place as the RWB7? It will make life easier as you can use the existing wires - there will be three or four (ignoring any wire connected to an earth terminal).

Check that you get good communication between proposed controller location and receiver before fixing the receiver in place.

isolator switch three returns:

------> fuse ------> burglar alarm (I think!)
------> RWB7I
------> boiler

The wires to the L and N terminals of the RWB7 go to the L and N terminals of the receiver.

You now have two options (depending on existing wiring):

1. One wire from RWB7 terminal 4: connect this to receiver terminal B and insert a link between L and A on the receiver; or

2. Two wires from RWB7 terminals 2 and 4: connect wire to 2 to receiver A; wire to 4 to terminal B.

 

[Retain81]

Thanks a lot, you've made this seem quite straightforward!

I was planning on putting the receiver in the same place as the RWB7 for the exact reason you mentioned

I'll have a look at the wiring tomorrow. We have a teething daughter refusing to sleep at the moment so I'm under strict instructions from the wife not to 'faff' with anything tonight...

Thanks again!

 

[Retain81]

Well, almost a year later I actually got around to doing this.

D_Hailsham - if you're still around, it was scenario 2 and the whole think took me about 15 minutes including mounting the transmitter on the wall.

It's all been working happily for a couple of weeks now and couldn't be more pleased with the results. Thanks for your help!