How close to boiler does a wireless receiver need to be?

[ewansdad]

Hi.

I was thinking of replacing our drayton digistat +2 programmable room stat with the wireless version. I want to do this because the stat is in the same room as a wood stove and is playing havoc with the settings.

I thought i could remove the digistat from the wall and fit the wireless receiver in its place? The wireless stat would then be put in a more suitable place - probably the hall as the lounge gets alot of solar gain. This would avoid the need to extend the wiring if i were to move the exsisting stat - wife does'nt like wires showing!

The drayton instuctions suggest putting the receiver near the boiler but our boiler is in a detached garage about 11 metres away from the room where the stat would be. The signal would have to go through a brick internal wall, the double skin exterior wall and the brick wall of the garage. Sounds to me like that would be asking too much. If the receiver was in the house the signal would only have to travel about 10ft and through one internal brick wall.

So to cut a long story short can i put the receiver in the house on the end of a lenghty cable which goes back to the boiler in the garage?

Thanks stu

 

[D_Hailsham]

1. I thought I could remove the digistat from the wall and fit the wireless receiver in its place?

2. Can I put the receiver in the house on the end of a lengthy cable which goes back to the boiler in the garage?

1. You need to check that you have a Neutral wire for the receiver. This is in addition to the Live and Switched Live wires.

2. Provided 1 is OK, there will be no problem.

 

[ewansdad]

Thanks Mr Hailsham.

There is a neutral but it is not used for the current stat. Its only a two wire connection - perm live and switched live.

I traced the wires back to the boiler and the blue neutral wire goes to a junction box above the boiler but it is'nt connected to anything. There is a spare core in the cable that goes from this junction box to the boiler PCB if that is the route it should take.

I suppose the connections depend on the boiler and stat wiring instuctions. Do neutral connections from programmable room stats go back to the boiler PCB or do they terminate in the junction box? Or are they different for different boiler/stat combinations?

Thanks, stu

 

[Agile]

The operating contacts are the same connections as the current room stat which is just two wires. One of them is live. You also need a neutral connection from anywhere as the receiver needs a live and neutral to obtain its power.

The wireless receiver can go anywhere and near the boiler might be the best place. You could still keep your existing room stat and have the two connected in parallel or series as double controls can have some advantages.

Tony

 

[ewansdad]

Thanks Tony.

So, i could use the redundant blue wire and take the neutral connection from the junction box where it connects to the fused mains inlet switch?

I dont know why the best place for the receiver would be near the boiler. Will a 12M cable have any effect on how the receiver works? I dont see how it can as the digistat +2 we have now works.

I'm just trying to get my head around the dual controls concept. Will have to draw out some circuit diagrams to try and get an understanding.

stu

 

[D_Hailsham]

I should have asked this earlier: which make and exact model boiler do you have?

It may affect your ability to locate the receiver in the same place as the exiting stat.

 

[ewansdad]

It's worcester greenstar heatslave 18/25 condensing combi oil boiler.

I think it was the drayton digistat +2 RF instructions which said the receiver should be near the boiler. Cant remember now, it could have been the boiler instructions.

Thanks, stu

 

[Agile]

The only requirement to do what you want is that there is a live mains feed to your existing roomstat which can be used to supply power to the receiver.

That was the common method until a few years ago when some makers started using low voltage thermostat connections. That trend is now reversing as it made fitting to older systems more difficult and some nupty installers were blowing PCBs by connecting mains to them.

There is no problem having 12m of cable but I still dont see why you dont want to put it at the boiler location!

Tony

 

[ewansdad]

Tony, my concern was the distance between receiver and room stat and the mutiple walls the signal would have to go through - 11M through internal brick wall, double skin exterior wall, across garden and through brick garage wall and all the junk thats in there.

stu

 

[Agile]

Its difficult to guess what the attenuation through your walls might be but the later ones have superhet receivers are are more sensitive than the older wideband ones with a super regenerative receiver.

My suggestion would be to fit it at the boiler and if there are any problems to then relocate it.

Tony

 

[D_Hailsham]

It's worcester greenstar heatslave 18/25 condensing combi oil boiler.

In that case you can fit the receiver where the existing stat is.

I think it was the drayton digistat +2 RF instructions which said the receiver should be near the boiler. Cant remember now, it could have been the boiler instructions.

It does not matter where the receiver is located relative to the boiler as all it is doing is acting as a switch for a 230V circuit - the same job as your existing stat is going!

As for make, Honeywell seem to have a better reputation than Drayton; and are easier to use. Look at the CM921 and CM927.

Wiring should be easy, but you need to check which terminals the existing stat connects to at the boiler. There are two Blocks X1 and X2 (see page 27 of the Installation Manual. You will probably find that they are connected to the Block X2, Ls and Lr terminals. If so move the wire connected to Ls to Block 1, L terminal. Also connect the Neutral wire to Block 1, N terminal. The reason for moving the wire is that the receiver needs a permanent supply and the Ls terminal is not permanent.

At the receiver:

Connect Live wire (from boiler L) to Live terminal
Connect Neutral wire (from Boiler N) to Neutral terminal
Connect Switched live (from boiler Lr) to SL terminal (B on the Honeywell)
You will also have to connect a link from Live to Common (A on the Honeywell).

That's the easiest way to achieve what you want without worrying if there will be any communication problems through several brick walls; and you can also see easily if the boiler is on by the green light on the receiver!

 

[ewansdad]

Thanks alot everyone. I've much to do with my heating system so i'd better get started. I'm sure you will be hearing plenty from me.

I have enjoyed learning about heating systems from here and the web in general - wish i'd become a heating engineer when i was younger!
stu