External Electrical Controls - Keston 30C Installation And Servicing Instructions

37 EXTERNAL ELECTRICAL CONTROLS

Wiring External to the Boiler
The fuse rating should be 3A.
Wiring external to the boiler MUST be in accordance with
the current I.E.E. (BS.7671) Wiring Regulations and any
local regulations.
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.
Note. If the boiler is installed in a garage it may be
necessary to fit a pipe thermostat, preferably on the
return pipework.
Earths are not shown for clarity but must never be
omitted.
OpenTherm Programmable Room Temperature Control
Note. These terminals MUST ONLY be connected to an
OpenTherm Controller, (such as the Keston Chronothern Room
Controller (c.17.4.21.00.0). Connecting any other device /
control wiring may destroy the primary PCB.
1. Isolate the mains supply to the boiler.
2. Remove the front panel. Refer to Frame 44.
3. Swing the control box down into the servicing position.
Refer to Frame 50.
4. Remove the control box cover. Refer to Frame 62, no's 3
and 4.
5. Unclip the 3 way in-line connector containing 2 purple
wires and 2 red wires.
6. Connect this 3 way connector to the 3 way connector
containing 2 purple wires wired from the 4 way terminal
block.
7. Connect the two wires from the OpenTherm
Programmable Room Temperature Control to the two LH
connections of the terminal block as shown.
8. Re-assemble in reverse order.
36
INSTALLATION
Programmable Room Stat
Use of General Live for Room Stat
Programmable
Optional
Room
Frost Stat
Stat
Mains In
Room Stat L N Frost Stat
Room
Optional
Stat
Frost Stat
Mains In
Room Stat L N Frost Stat
5
6
Keston 30C -
Installation and Servicing
3G9990a
7