wireless room thermostat

[daverichardson]

Hi evryone and please help.
I have an existing worcester 280rsf boiler that has worked fine for years and I want to install a remote wireless room thermostat (honeywell cm927 or similar) but I am unsure of the wiring. At the moment the boiler is either on or off and I want more control.
The existing system is as follows
A fuse to a programmable digital timer and then a 5 core wire from the timer to the boiler
Inside the boiler the Brown is connected to the top terminal of block X4 (I will call this 4)
The Blue is connected immediately below (3)
The Green yellow is connected to the bottom terminal (1)
Another Green yellow comes out of terminal (2) to earth but nothing goes in. Is this correct?
The other 2 wires are black and go to block X5 both are routed to terminal (2) of this block second from bottom and I assume this is the link i have read about. It is in the section labelled room stat and has three terminals in this section.
Two more terminals (above) are also in this block X5 labelled frost stat and are not in use
So how do I wire up the honeywell receiver? which i have not bought yet!
I also have rad valves some in use some not but that is another problem for another day
Please help in simple terms if you can
thanks
dave

 

[D_Hailsham]

Inside the boiler the Brown is connected to the top terminal of block X4 (I will call this 4)
The Blue is connected immediately below (3)
The Green yellow is connected to the bottom terminal (1)
Another Green yellow comes out of terminal (2) to earth but nothing goes in. Is this correct?

3 and 4 are correct but, according to the manual. the green/yellow should go to the earth terminal not to 1. 2 is OK

The other 2 wires are black and go to block X5 both are routed to terminal (2) of this block second from bottom and I assume this is the link i have read about. It is in the section labelled room stat and has three terminals in this section.

Can you find out what happens at the other end of the 5-core cable?

Two more terminals (above) are also in this block X5 labelled frost stat and are not in use

You only need a frost stat if the boiler is located in a garage etc where the air temperature could drop very low.

What is the existing programmer - make and model?

 

[daverichardson]

Hi and many thanks for the quick reply

The programmer make looks like
ACL Lifestyle model LP711
I do not have a manual for this.

I agree with your note on the green yellow being in two separate teminals wiring which is why i raised the point in the first place
Is this dangerous at the moment?
As i say i have had no problems with the system at all

thanks for clearing up the frost thermostat bit too

look forward to your reply
dave

 

[daverichardson]

oops
the other end of the five core cable comes direct from the programmer, i have not looked in there
do you want me too and if so how?
dave

 

[D_Hailsham]

the other end of the five core cable comes direct from the programmer, i have not looked in there
do you want me too and if so how?

Yes please.

There is a screw on the underside of the LP711. Release this and you can hinge the unit up and away from the backplate. Might be a good idea to turn the power off before you remove or the terminals on the back will be live. Just tell me what is connected to each terminal.

 

[daverichardson]

HI
Here we are again and thanks for the help so far.
I switched off the fused unit next to the programmer LP711 and removed the 3Amp fuse.
i removed 2 screws from the base of the programmer and lifted the unit off the wall. on the rear of the unit is a wiring diag corresponding to 6 terminals still on the wall. The terminals are marked on the diag as
N L 1 2 3 4
1 is labelled comm
2 is labeled off
3 is labelled on

The actual wiring in place is as follows
From the fused unit to the programmer we have three core
Blue going to the first terminal (N)
Brown going to the second terminal (L)
Green yellow to an earth

From the programmer to the boiler we have five core
Blue going to the first terminal (N) common with above
Brown going to the second terminal (L) common with above
Green yellow to earth common with above
There are also two black wires commoned up leaving the fifth terminal from the left which is ON according to the wiring diag

In addition there is black wire looped between the second terminal from the left (L) and the third terminal from the left which is (1) COM on the diag

Hope this helps

 

[D_Hailsham]

The wiring as just as I thought it would be. The two black wires have been commoned to prevent one accidentally touching a wrong terminal if it was loose.

The CM927 relay box could be placed in the same place as the LP711, but I suspect you want to put the control unit there. In that case, mount the relay box near the boiler (see instructions for suitable location).

The boiler needs a permanent LNE supply; at present this comes from the fused spur via the LNE terminals of the LP711.

The relay box only needs a mains supply to the L and N terminals (no earth as it is insulated). This can come either from the same fused spur or from the boiler's L and N terminals.

Lastly you need an on/off connection from the relay to the boiler - equivalent to the black wires. There are two ways of doing this:

1. Link L to A in the relay and connect a wire to B and other end to same terminal as existing black wire (X5/T2)

2. Connect a wire to A and a second to B. At the other end connect one to X5/T2 and the other to X5/T3.

 

[daverichardson]

WOW, great I almost understand it. many thanks but a couple of queries
It would be my intention to replace the LP711 with the new receiver and keep the transmitter down stairs in a room as yet to be decided.
So,
1) Could I take the earth from the existing fused unit and connect it to the earth wire from the boiler in a separate block?
2) The wiring in the boiler (you may recall) is not as per diag with regard to the earth cable being in two separate terminals. the earth is into terminal
1 X 4 from the existing LP711 and out from the terminal above it to the earth point, please advise
3) I am not quite sure of the notes regarding the new receiver (since I have yet to purchase it) I guess the lettering will become obvious when I do get it
4) I only chose the CM927 because it looked ok and a reasonable cost
5) If i need additional wiring to hook up from the CM927 to the boiler is there a particular type
Finally I think (!) when this little project is finished I need advice on positioning CM927 and boiler settings and rad valves, are you the right guy to talk to (no offence) But that is for another day.
Many many thanks for the help you have given me
dave

 

[D_Hailsham]

It would be my intention to replace the LP711 with the new receiver and keep the transmitter down stairs in a room as yet to be decided.

I had thought of that, but decided it might be a bit complicated because of the earth wire!

1) Could I take the earth from the existing fused unit and connect it to the earth wire from the boiler in a separate block?

Yes!!

2) The wiring in the boiler (you may recall) is not as per diag with regard to the earth cable being in two separate terminals. the earth is into terminal
1 X 4 from the existing LP711 and out from the terminal above it to the earth point, please advise

This is what the boiler manual shows:

280RSF wiring

• D_Hailsham
• 28 Jun 2012
• 1

Mains wiring and connections for CM92X wireless stat

As you can see the incoming earth wire connect directly to the earth terminal, not to X4/T1. There is then a connection from earth terminal to X4/T2. There must be a good reason for this, so I suggest you do the same.

3) I am not quite sure of the notes regarding the new receiver (since I have yet to purchase it) I guess the lettering will become obvious when I do get it
4) I only chose the CM927 because it looked ok and a reasonable cost

All will be revealed when you read the instructions (I hope )

5) If i need additional wiring to hook up from the CM927 to the boiler is there a particular type

Doing it your way is actually the easiest and you can use the existing wires as follows:

LP711 - CM927 - boiler

L (both) - L - (one) - L
N (both - N - (one) - N
E (both) - Terminal block - (one) - E terminal
Black 1 - A - X5/T3
Black 2 - B - X5/T2

Finally I think (!) when this little project is finished I need advice on positioning CM927 and boiler settings and rad valves, are you the right guy to talk to (no offence)

There are plenty of other contributors who can advise you on this. It's just a case of who reads your problem first! But as a starter, the CM927 controller should, ideally, be in a room/area which does not have a TRV on the rad. This is because they can conflict with each other (the one set to the lowest temperature wins). If you already have a TRV you can set it to max and the CM927 will then work OK.

 

[daverichardson]

Absolutely fantastic you are a hero and I owe you a pint
I will leave the thread ope for a while until i get all the bits together
many many thanks
dave

 

[daverichardson]

Hi again,
Just received a Honeywell CMT927 and I have been checking it out with reference to your recent most helpful advice.
Inside the receiver are six terminals
A, B, C You mentioned using A & B for the existing black wires - good

On the other side (lhs) there is N, L, L terminals
I am unclear on the two L terminals

Do I take the L from the Fused box and connect to one of the L terminals in the CM
and
take the L from the boiler and connect to the other (second) L terminal in the CM
Sorry to be a dumpling but I don't want to blow it up!!
I will give the manual a good read before I start the installation

 

[Dan Robinson]

The left of the two L's is for powering the device from your fused spur/wiring centre/boiler.

The second L is for providing mains voltage to the switching circuit if you need it. In this case, link the L to A. Be then goes back to your valve/boiler.

If the wire leading to A is already 240V then you don't need to bother.

 

[D_Hailsham]

Inside the receiver are six terminals
A, B, C You mentioned using A & B for the existing black wires - good

Correct.The C terminal is used when you are controlling a cooling system

On the other side (lhs) there is N, L, L terminals
I am unclear on the two L terminals

Do I take the L from the Fused box and connect to one of the L terminals in the CM and take the L from the boiler and connect to the other (second) L terminal in the CM

That's what I would do.

[code:1]

Supply Relay Boiler
L--------------L
L --------------L
N--------------N---------------N
E-----------Terminal-----------E
A-------------X5/3
B-------------X5/2
[/code:1]

I will give the manual a good read before I start the installation

That's the difference between the amateur and the pro - they don't presume they know everything.

Note to Dan
Normally I would recommend your way, but the OP's situation is slightly different.

 

[daverichardson]

All,
Thank you for your kind assistance throughout,
I will probably start the installation tomorrow, now i am clear on what is required
dave

 

[daverichardson]

HELP
I connected the wiring up as discussed and got the transmitter talking to the the receiver.
I increased the temp on the transmitter to get the boiler to fire up and nothing.
The boiler works on demand from the hot water tap, so i must have done a connection wrong, but which one?
i will begin to check the wiring while I wait for your reply
thanks