15
Concord CXS -
Installation & Servicing
14 ELECTRICAL CONNECTIONS
INSTALLATION
INST
ALLA
TION
Connection must be made in a way that allows complete
isolation of the electrical supply - such as a double pole
switch, having a 3mm (1/8") contact separation in both poles,
or a plug and socket serving only the boiler and system
controls. The means of isolation must be accessible to the
user after installation.
This should serve only the boiler, together with its controls
and pumps. The unswitched live supply, which the boiler
requires to allow the pump overrun facility to operate, should
be controlled by the above switched/fused supply, but
should connect from there directly to the boiler and not via
any automatic time or temperature controls.
The switched live supply should be subject to control by
time and temperature controls in the usual way.
The controls incorporate a pump overrun facility, which is
necessary to dissipate residual heat on plant shutdown. It
is essential therefore that the main pump (and shunt pump
if fitted) is wired to the pump terminals marked L2, N and
Earth on the plug-in terminal strip on the top box at the rear
of the control box.
The main supply to the boiler must be wired to the boiler
terminals L1, N and Earth on the plug-in terminal strip. This
live connection must be unswitched, that is a supply not
interrupted by any automatic temperature or time control,
to enable the pump overrun (and the frost protection facility)
to operate.
Failure to operate this procedure will result in nuisance
overheat thermostat operation.
If a down draught flue thermostat is to be fitted then the link
(marked TTB) should be removed from the plug-in
connector.
The internal wiring of the boiler control box is shown in Frame
15.
Wiring should be in four core PVC insulated cable, not less
than 0.75mm
2
(24/0.2mm). All fuses must be ASTA approved
to BS. 1362.
The length of the conductor between the cord anchorage and
the terminals must be such that the current carrying conductors
become taut before the earthing conductor, if the cable or cord
slips out of the cord anchorage.
The boiler can be controlled either by volt-free external contacts
connected between terminals X1 and X2 or by a switched live
supply brought to X2 (after removal of the factory-fitted link between
X1 and X2), accompanied in each case by a permanent live supply
to terminal L1.
If a separate frost thermostat is fitted it must be wired across
the time switch contacts and if frost is likely the system should
be turned off using the time switch settings - all other controls
including the boiler thermostat knob should be in the normal
running position.
The earth connection MUST NEVER be omitted.
Wire the earths as shown in Frame 13.
All wiring between entry at the rear of the boiler and the
connection box must be secured neatly under the cable clips
provided.
Wiring must never be allowed to come into contact with the hot
boiler body.
If a flow switch is fitted, it should be wired between F
1
and F
2
or
the terminal plug-in connection on the bottom box at the rear of
the control box.
Do not wire these connections in conduit up to the boiler as
this will make it impossible to remove the control box for
servicing or maintenance.
14A ELECTRICAL CONNECTIONS
Remove the 2 screws from the box at the bottom of the control box
back panel and push in the terminal plug-in connector containing
the gas valve wiring harnesses. Secure with the 2 screws.
Fit the earth terminals to the earth post at the LH side of the control
box back panel.
Check that the flame detector lead is properly connected to the
flame detector electrode on the RH burner.
