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20
2.6.3 External Controls
External heating controls should be connected to the appropriate terminals numbered in
diagram 2.6.2b
.
WARNING: ALL EXTERNAL CONTROLS MUST NOT BE TAKEN FROM ANY OTHER POWER
SUPPLY OTHER THAN VIA THE
3 AMP FUSED ISOLATING SWITCH MENTIONED ABOVE.
ELECTRICAL CONNECTIONS
2.6.4 Supply cable connection [24 HR Supply]
Caution:
To prevent an induced current from switching the central heating on when not required it is
important that the heating system control cables are separated from the other mains cables.
There is provided 1 or 2 heat resistant cables extending from the main panel situated between
both circulating pumps depending on the tariff being used. One cable has 3 cores. Live, Neutral
and earth to be connected to a 3 amp double pole fused isolator.
The other cable has 2 cores coloured brown and (blue core covered with brown sleeve) these are
both common live and switched live wires to be connected to external heating controls.
If the boiler is being connected to an E10 tariff the 3 core flex if already fitted, must be removed
and a link fitted between terminal 1 & 2 as shown in diagram 2.6.2b on page 18.
It is also advisable to fit the off-peak control when using a wet electric tariff other than Domestic
& Economy 2000 to enable a reduction in running costs.
IMPORTANT
If the boiler is connected to Scottish Power Domestic & Economy 2000 tariff it requires a
permanent mains supply through an external isolator (rated to 3amp) which must isolate any
heating system controls see
diagram 2.6.2b
Any heating system controls must not interrupt the mains supply to the boiler.
Standard colours are
Brown- Live, Blue- Neutral and Green and yellow- Earth
. Make the earth cable
of a greater length so that if the cable becomes strained the earth would be the last to become
disconnected.
CAUTION: IT IS ESSENTIAL
TO MAKE SURE THAT THE POLARITY IS CORRECT.
2.6.5 Heating system controls
All external controls and wiring are required to provide a minimum of reinforced insulation at 250 vrms
between the parts of those devices operating at mains hazardous voltage and the user accessible parts
of those devices.
Note: for further information, see the building regulations 1991- conservation of fuel and power, 1995
edition- appendix G, table 4B.
When any kind of external heating system controls are being used to regulate the heating system
connect a single pole type, to the appropriate terminals of the connector shown in
diagram 2.6.2b, or (to
the 2 core cable provided).
If the installation requires p
rotection by a “Frost Thermostat” connect a single pole type,
between
terminals 6 and 9
shown in
diagram 2.6.2b.
