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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 2 heat resistant cables extending from the enclosure situated between both circulating
pumps. 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.
The boiler 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 permanent 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 protection by a “Frost Thermostat” connect a single pole type, to the
appropriate terminals of the connector shown in
diagram 2.6.2b.
2.6.6 Electrical Test
Carry out preliminary electrical system checks as below.
1) Test insulation resistance to earth of mains cables.
2) Test earth continuity and short circuit of all cables.
3 Test the polarity of the mains.
4 Refit the enclosure cover.
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