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18
INSTALLATION INSTRUCTIONS - Page 18
Figure 19 PRINCIPAL OF WIRING
WIRING
WARNING:
This appliance must be earthed.
The boiler and all external control circuit wiring must be
supplied from the same single isolating switch and should
be fused at 3A.
Care must be taken to ensure that all wiring to the boiler is
kept clear of sharp edges and hot surfaces.
Ensure that the earth conductor is longer than the L, N, and
SWL from the point of anchorage, so that the current
carrying conductors become taut before the earth
conductor, if the cable is pulled out of the cable clamp.
The boiler terminal block which is situated in the control box
is not designed to accept wiring from all the on site controls
and therefore the installer will usually need to incorporate a
suitable junction box or Potterton electronic Programmer.
The principle of wiring is shown in Fig 19. It should be
noted that the pump must be wired directly to the boiler
terminal block on FULLY PUMPED systems and to the
junction box or programmer on combined GRAVITY HOT
WATER/PUMPED CENTRAL HEATING
systems.
Figure 20 ACCESS TO THE BOILER
ELECTRICAL TERMINAL BLOCK
Remove control box securing screw and lower the control
box to gain access to the boiler terminal block.
Figure 21 WIRING THE BOILER FOR A FULLY PUMPED
SYSTEM
Route a four core cable through the plastic bush at the rear
of the control box and the cable clamp as illustrated Fig 21,
and connect it to the boiler input terminals as follows:-
Permanent live to terminal marked MAINS ‘L’
Neutral to terminal marked MAINS ‘N’ Earth to terminal
marked MAINS
Switched live from external controls to terminal marked
MAINS SwL.
If there are no secondary controls fitted connect the SwL
terminal to permanent live in the external junction box.
Secure the cable within the cable clamp by tightening the
securing screws.
Following the pump manufacturers instructions connect the
pump supply wires to terminals marked PUMP, L, N and
on the boiler terminal block.
Route the cable through the plastic bush in the rear of the
control box and cable clamp as illustrated Fig 21. Secure
cable in cable clamp by tightening the two securing screws.
Close control box and replace securing screw.