28
INSTALLATION
isar + programmer -
Installation and Servicing
34 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.
Room Thermostat
If the thermostat has a neutral connection, use it (it provides
for more energy efficient operation by reducing switching
temperature differentials).
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.
The frost thermostat should be sited in a cold place but
where it can sense heat from the system.
L
3
L2 L1
N
Room 'stat
N
if required
nm8428
A
M
ains in
System
controls
System
Controls
L
N
nm8429
Diagram A
shows an application to boilers fitted with a room
thermostat only.
Diagram B
shows the fitting of a frost thermostat. An option kit
must be purchased to allow this.
Earths are not shown for clarity but must never be omitted.
INST
ALLA
TION
202851-1new.pmd
17/11/2006, 07:40
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