upgrade heating controls

[Bigken1]

Hi i have a old worcester 240 BF boiler that is controled by an Randall 103 clock no room thermostat. I am looking to install a honeywell cm921 wireless room statand timer. On taking the 103 off it is wired up from fuse plug to clock with
L- 6
N- 5
e- e
then from boiler to clock it has 1 wire
L-6
N-5
E-e
And another wire
brown - 1
Blue/black-2
can i do away with the second wire into the live and neutral and fit the blue/black wire into A and brown into B on the reciever. Or does the second wire from boiler need to go into the L&N on receiver aswell.What happens to the earth?

thanks in advance

big ken

 

[D_Hailsham]

On taking the 103 off it is wired up from fuse plug to clock with
L- 6
N- 5
e- e
then from boiler to clock it has 1 wire
L-6
N-5
E-e

This boiler requires a permanent mains supply; this is provided by the cable clock to boiler.

can i do away with the second wire into the live and neutral

No - if you did the boiler would not work!

does the second wire from boiler need to go into the L&N on receiver as well.What happens to the earth?

Yes. The L, N and E from fuse plug goes to the CM921 receiver and then on to the boiler. As there is no earth terminal on the receiver (not required), you will have to join the two earth wires using a terminal block

another wire
brown - 1
Blue/black-2

Do you mean: Blue/black-3? Terminal 2 of the Randall is not used!

fit the blue/black wire into A and brown into B on the receiver.

Need to know which terminals in the boiler this cable is connected to.

 

[Bigken1]

cheers
Sorry it was into terminal 3 on the randal and the brown wire is into terminal 1 and black into terminal 3 at the boiler

Ken

 

[D_Hailsham]

the brown wire is into terminal 1 and black into terminal 3 at the boiler

Is this Terminal Block X4 or X10? There are five terminal blocks along the front; X4 is the middle one. X10 is in the back left corner? Are you sure it's 1 and 3 at the boiler?

 

[Bigken1]

The wires go into x4 brown into 1 black into 2 says room stat under.

Cheers Ken

 

[D_Hailsham]

The wires go into x4 brown into 1 black into 2 says room stat under.

That's OK then.

The two wires to X4 connect to the A and B Terminals on the receiver. It's not essential which way round but Brown to A and Black to B is preferable.

 

[Bigken1]

Cheers Upgrades complete

thanks very much.

Ken