Help with buying and wiring a new wireless thermostat

[Wialli]

Hi All,

I want to install a wireless thermostat to my boiler - A Baxi Combi 105e boiler.

I've added a picture of the current wired thermostat which has 4 wires going into it, Yellow/green, black, brown and blue.

I've done a bit of online research, and it's been quite difficult to find any thermostats that have wires that correlate to these 4 colours. Some are 4 wired but with different coloured wires to those on mine, plus there are some that are 2 wired, some that are 3 wired.

From what I've read, some of these cables are (or can be) redundant, so do I need a 4 wired thermostat for all 4 wires, or could I also open up my options to a 3 or 2 wire model.

So I have 2 questions:

1. Help with the wiring of your suggested thermostat in point 1. - i.e. can I use a 2 or 3 wire product and if so which cables do I use from the picture (and what do i do with the other redundand cables?) - and if I do need to use all 4 cables then what colours on the picture should match up with the colours listed on the newer models.

2. Recommendations for a wireless thermostat between £50-120 with a visually attractive wireless box and decent/easy to use time settings controls - based on the wiring options in point 1!

Any help would be appreciated.

Thanks,
Wialli

 

[D_Hailsham]

You have taken the photo of the thermostat from the wrong side.

Remove the stat from the black backplate and then take a pic of the backplate, so we see the other side.

Are you replacing just the thermostat? If yes, which timer/programmer do you have?

Wire colours frequently are meaningless; you have to work it out from scratch.

 

[Wialli]

Ahhh ok!

I'll take another picture tonight of the front and the other side of the plate.

Yes, just need to replace the thermostat I think. It looks something like this but I think the 1-30 are the other way round and this only apparently has 3 wires:

http://www.wickes.co.uk/Drayton-RTS8-Room-Thermostat/p/228387

Will post later on...

 

[St0rmer66]

One wire is probably an earth, so realistically you have a 3-wire stat already. If you're going wireless then you'll be using all of the wires anyway, the receiver will need a permanent live, neutral and a switched live (and earth). If your 4th wire isn't actually an earth then it's probably for the "common" or "supply" wire when using low voltage/voltage free switching for the boiler (the receiver powered by mains 240v, then the common to switch live can be 24v). Pretty sure your boiler using mains switching though, in which case the common/supply is just linked to the permanent live behind the receiver.

 

[D_Hailsham]

Pretty sure your boiler using mains switching though, in which case the common/supply is just linked to the permanent live behind the receiver.

Yes, the boiler does have mains switching but, as the OP intends keeping his current programmer, you can't link the common to the permanent supply.

 

[St0rmer66]

Pretty sure your boiler using mains switching though, in which case the common/supply is just linked to the permanent live behind the receiver.

Yes, the boiler does have mains switching but, as the OP intends keeping his current programmer, you can't link the common to the permanent supply.

I had assumed he would be fitting a programmable thermostat that's why.

 

[Wialli]

I don’t really understand this “mains switching” and “programmer” of which you speak.

I did want the wireless thermostat to both control the temperature and programme the timer. So I’d remove the old thermostat with the 4 wires in as shown in the picture, and wire this into the receiver part of the wireless thermostat.

There is still the timer dial on the boiler itself, but I was hoping that the new wireless thermostat would supersede that taking control of the timer as well. Is that not the case, or is that some kind of bigger job altogether?

 

[St0rmer66]

I don’t really understand this “mains switching” and “programmer” of which you speak.

I did want the wireless thermostat to both control the temperature and programme the timer. So I’d remove the old thermostat with the 4 wires in as shown in the picture, and wire this into the receiver part of the wireless thermostat.

There is still the timer dial on the boiler itself, but I was hoping that the new wireless thermostat would supersede that taking control of the timer as well. Is that not the case, or is that some kind of bigger job altogether?

Not a big job, it just means I was right .

Yes the receiver would replace the stat. Then the new stat can go where you want it. Just set the timer on the boiler to constant and let the new stat take over.

 

[Wialli]

Always trust a Yorkshireman ey!

 

[Wialli]

Evening,

So have posted a couple of pics more while watching A Question Of Sport.

These are of the front of the 'stat' and of the reverse of the plate where the wires go (and before you start panicking, I did turn all the electrical sockets off before I did this).

So on the back, I know it's hard to read but they are across the top from left to right - N L 1 2 3 4, and on the side it looks like a 1 and the funny aerial symbol which I believe is the Earth symbol. So the wires are:

Blue - N
Brown - L
Black - 3
Yellow/Green - Earth

I'm guessing to you that makes sense. So if I buy a new wireless stat with programmer as well, do I need to buy a 4 wire one and make use of all of these wires, can I buy a 3 or a 2 wire one, and if so which wires do I leave out. And what do I do with those wires, just leave them loose?

And as an additional question - how do I set the boiler to constant so the wireless stat takes over? Google was not helpful on this matter.

 

[St0rmer66]

I think you're getting yourself a bit confused. A wireless receiver will always need at least 3 wires (earth isn't counted when they say "2-wire" or "3-wire". The thermostat and receiver sets you're looking at shouldn't be saying that though. Make sure you're not looking at wired by accident.

 

[Wialli]

Ah I see. thanks for the clarification. So even the ones that say 2 wire are going to be 3 as they will all include earth as standard!

So these should all be ok and compatible:

Grasslin
http://www.toolstation.com/shop/p56488
http://www.toolstation.com/shop/p53555

Drayton
http://www.screwfix.com/p/drayton-d...at/76816#product_additional_details_container

Horstmann
http://www.screwfix.com/p/horstmann-hrfs1-programmable-room-thermostat/93829

Siemens (says 2 wire installation)
http://www.screwfix.com/p/siemens-rev24-rf-7-day-programmable-wireless-digital-room-thermostat/64741

Any recommendations? I looked at the CM927 as everyone seems to rave about it, and it didn't get amazing reviews on Amazon.

Also, how do I set the Baxi Combi 105e to "constant". I looked at the boiler and there was no "constant" setting.

 

[St0rmer66]

Not sure about the others but if you get the Drayton one it will come with a backplate almost exactly the same as the one on your current stat. Only difference will be that you put a link in from "L" to "1"... other wiring the same (brown to L, blue to N, black to 3).

Just set the current timer on the boiler to "1" or "on" all the time. Is it a dial with a lot of tappets round the edge which you put in or out from the middle to determine the on/off times?

 

[D_Hailsham]

The first Grasslin you gave a link to is just a thermostat, it's not a programmable one.

As for Honeywell CM927, all I can say is that I have had one for nearly eight years and it has worked perfectly. No sign of the screen failing. The poor reviews on Amazon suggest that there has been a bad batch. Honeywell are very good when it comes to replacing faulty items.

 

[Wialli]

Morning Guys,

Happy Friday. Thanks for the advice given so far. I'm starting to get this straight in my head. I'm therefore thinking either the Drayton one linked above or I may take your advice D_Hailsham and go for that CM927.

St0rmer66 - how do I link L to 1? Take a spare bit of the brown cable and run between the two ports?

I've attached pics of the controls. I know which one you mean with the bits that you push in but this is different. It's (as seems to be with most timers) confusing as hell to set the timer, so we literally just switch it on when we get home and off when we leave, meaning for a freezing house when we get home.