2.21 EXTERNAL WIRING
External Controls – 230 V 50 Hz
Wiring a 230 V Programmable Room Stat (Diagrams A & C)
or 230 V Timer & Room Stat (Diagram B).
1. Remove the link wire from the room stat/timer
connection.
2. Connect the external cable from the room stat/timer
across this connection. If a general live connection is
used for the room stat or timer then connect this to the
fused spur, on the load side (see Diagram C).
3. If the room thermostat has compensation and requires
a neutral connection, make this connection to the fused
spur, on the load side.
Optional External Controls – Extra Low Voltage
Wiring OpenTherm Programmable Room Stat (Diagram D).
1. Remove the timer link plug inside the timer option cover,
located on the front of the control box.
2. Unclip the timer link socket from the aperture on the rear
of the control box, locate the plug on the same harness
branch and connect these together.
3. Using the rubber bung located adjacent to these
connections, insert it into the open aperture.
4. Connect the external cable from the OpenTherm
Programmable Room Stat on the RHS of the boiler
installer connections, labelled OpenTherm.
Frost Protection
If parts of the pipework run outside the house or if the
boiler will be left off for more than a day or so then a frost
thermostat should be wired into the system.
This is usually done at the programmer, in which case the
programmer selector switches are set to OFF and all the
other controls MUST be left in the running position.
The frost thermostat should be sited in a cold place, but
where it can sense heat from the system.
Wiring a system frost thermostat, see diagrams E. Wire the
frost thermostat across the two connections as shown.
If the boiler is installed in a garage it may be necessary to fit
a pipe thermostat, preferably on the return pipework.
L
N
Room
Stat/
Timer
Programmable
Room Stat
Diagram A: 230 V
L
N
Room
Stat/
Timer
Room
Stat
Timer
Diagram B: 230 V
Timer & Room Stat
L
N
Room
Stat/
Timer
Room
Stat
Mains In
Diagram C: 230 V
Programmable Room Stat
Use of Live from Isolator
Open
Therm
OpenTherm
Programmable
Room Stat
Outside
Sensor
Diagram D: OpenTherm
Programmable Room Stat
Frost
Stat
Op
�
onal
Frost Stat
Diagram E: 230 V
Op
�
onal Frost Stat
Programmable Room Stat
28
Installation and Servicing
Section 2 - Installation
INST
ALLA
TION