20
classic m -
Installation & Servicing
INSTALLATION
29 EXTERNAL ELECTRICAL CONTROLS
Wiring external to the boiler MUST be in accordance with the
current I.E.E. (BS.7671) Wiring Regulations and any local
regulations.
The fuse should be 3A.
Room Thermostat
If the thermostat has a neutral connection use it. (It provides
for more energy efficient operation by reducing switching
temperature differentials.)
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 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.
Designation of the terminals will vary but the programmer and
thermostat manufacturers' leaflets will give full details.
Diagram A
shows an application to boilers fitted with a room
thermostat only
Diagrams B and C
show applications to boilers fitted with
alternative time controls.
Earths are not shown for clarity but must never be omitted.
L3
L2 L1
N
Room ’stat
N
if required
Optional Frost ’stat
Ecl 1543
A
Mains in
System controls
L3
L2 L1
N
Room ’stat
N
if required
Optional Frost ’stat
Ecl 1544
B
Mains in
System
controls
L3
L2 L1
N
Room ’stat
N
if required
Optional Frost ’stat
Ecl 1545
C
Mains in
System
controls
28 INTERNAL WIRING
Incoming mains
wiring detail
A pictorial wiring diagram is shown in Frame 29 .
1.
Route the mains cable into the bottom Rear centre of the boiler.
2.
Wire the live and neutral and earth wires into the plug.
Note.
Ensure that the lengths of the current carrying conductors
are shorter than the earth conductor so that if the cable slips in its
anchorage the current carrying conductors become taut before the
earth conductor.
3.
Secure the mains lead with the cable clamp.
4.
Reconnect the mains lead plug. Ensure it is fully located.
Note.
Wire any switched live supply into L2.
Ecl 1542
Mains Plug
(supplied in hardware pack)
Socket
(fixed to boiler)
Remove link when connecting external programmer.
Ecl1257
L3
N
L2
L1
INST
ALLA
TION
Summary of Contents for Classic m3050
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