20
Installation and Servicing
SECTION 2 - INSTALLATION
2.8 EXTERNAL WIRING
L
N
Room
Stat
Frost
Stat
DIAGRAM A:
Programmable Room Stat or
Room Stat with Internal Timer
DIAGRAM B:
Room Stat with External Timer
Mains In
DIAGRAM C:
Use of General Live for Room Stat
Optional Room Stat /
Programmable Timer
Optional Frost Stat
Optional Room Stat /
Programmable Timer
Optional Frost Stat
Optional Frost Stat
L
N
Frost
Stat
Room
Stat
Room Stat with timer
L
N
Stat
Room
Stat
Frost
L
N
Room
Stat
Frost
Stat
DIAGRAM A:
Programmable Room Stat or
Room Stat with Internal Timer
DIAGRAM B:
Room Stat with External Timer
Mains In
DIAGRAM C:
Use of General Live for Room Stat
Optional Room Stat /
Programmable Timer
Optional Frost Stat
Optional Room Stat /
Programmable Timer
Optional Frost Stat
Optional Frost Stat
L
N
Frost
Stat
Room
Stat
Room Stat with timer
L
N
Stat
Room
Stat
Frost
L
N
Room
Stat
Frost
Stat
DIAGRAM A:
Programmable Room Stat or
Room Stat with Internal Timer
DIAGRAM B:
Room Stat with External Timer
Mains In
DIAGRAM C:
Use of General Live for Room Stat
Optional Room Stat /
Programmable Timer
Optional Frost Stat
Optional Room Stat /
Programmable Timer
Optional Frost Stat
Optional Frost Stat
L
N
Frost
Stat
Room
Stat
Room Stat with timer
L
N
Stat
Room
Stat
Frost
DIAGRAM D:
OpenTherm Device
DO NOT CONNECT 230V TO THESE
TERMINALS OR THE HIU ELECTRONICS
WILL BE DAMAGED
Outside
Sensor
Open
Therm
OpenTherm Device
E.G. Honeywell OT
Bridge R8810
External Controls – 230V 50Hz
Wiring a 230Vac 50Hz Room thermostat,
Diagram A (with optional timer, Diagram
B)
1. Connect the external cable from the
room thermostat/timer across the
terminal labelled ‘Room Stat’. See
Diagram A.
2. If the room thermostat has
compensation and requires a neutral
connection, make this connection to
the fused spur on the load side. See
Diagram C.
Optional External Controls – Extra Low
Voltage
Wiring OpenTherm Room Control or other
OpenTherm Master Device, Diagram D.
1. Connect the two OpenTherm cables
from the external OpenTherm
controller into the terminals labelled
‘OpenTherm’. See Diagram D.
2. Ensure no other controllers are
connected to the High Voltage
‘Room Stat’ connection as this will
prevent the HIU/OT+ communication
functioning correctly.
Frost Protection
If parts of the pipework run in areas subject
to cold temperatures or if the HIU will be left
in the ‘Off’ state for more than a 1-day period
a frost thermostat should be wired into the
system. The frost thermostat should be sited
at coldest point in a system such that I can
sense heat from the system.
Wire a system frost thermostat to the
terminals labelled ‘Frost Stat’ as detailed in
diagrams A, B and C.
2.7 INSTALLER WIRING
The image below shows the HIU electrical connections.
The HIU must be connected to a permanent live supply via the
‘L’ ‘N’ and ‘GND’ connections and not switched by thermostats/
programmers. The installer wiring must be inserted through the
rubber grommets in the base of the HIU and securely clamped
by the cable retention bars to prevent strain on the terminal block
connections.
Accessing the installer wiring
1.
Isolate the mains supply from the HIU.
2.
Open the drop-down cover and remove the front access
panel. Refer to Section 3.4.
3.
Gently swing down the control box into the service position
to expose the installer connections.
All the installer connections can now be easily accessed. Once
any wiring is complete, to ensure the HIU is safe, rebuild the
unit in the reverse order above.
ROOM
STAT
FROST
STAT
N
L
OUTSIDE
SENSOR
OPEN
THERM
MBUS
INST
ALLA
TION
