33
Concord CXi - Installation
50
BOILER CONTROL
FAULT FINDING
user, the boiler will go to low rate and when the temperature
reaches the set point plus 3 °C the low rate gas valve will
close. When the temperature falls 2 °C the boiler will start at
low rate and remain there until the temperature falls to the set
point less 2 °C then the high rate gas valves will operate.
On start up, the high rate gas valves will operate immediately
after detection if the boiler flow rate is greater than 55 °C.
In order to determine the continued correct operation of the
control, every 4 hours the boiler will shut down for a maximum
of 30 seconds to do a self-check operation and restart
automatically.
The control will display the number of operational hours of the
boiler to the nearest hour and cannot be reset.
The boiler thermostat has a range of 60
o
C-85
o
C, in 1
o
C
steps, with an accuracy of ± 2
o
C and hysteresis of 3
o
C.
The full sequence control enables 5 attempts at ignition, with 1
minute intervals between attempts, followed by nonvolatile
lockout if detection does not take place.
If the [0/1] switch on the front panel is at "Standby.....0" then
the pump will continue to run indefinitely. In this state the frost
protection can not operate.
In "Lock-out" the pump will continue to run only if the
temperature is greater than 75
o
C. If it is less then the pump
will be OFF.
FAULT FINDING
The boiler control has a unique fault diagnostic feature which
can, in the unlikely event of a failure, display a message
indicating the nature of the fault to assist a speedy and
effective repair.
The faults that are diagnosed are; overheat thermostat, pump,
boiler sensor, gas valve(s), air pressure switch (if fitted), fan (if
fitted), float switch (if fitted), outside sensor (if fitted) with
indication of combustion lockout.
In the unlikely event of a fault the display will indicate precisely
the fault and give a step by step indication of the method of
correcting the fault.
If the HT generator should cease to function it is impossible to
automatically display this condition. Should this fault occur
then:-
would be displayed and the subsequent display screens
would direct attention to the spark generator.
Should a gas valve fail, the diagnostics will indicate that it is
valve 1 or 2 that is at fault. If the boiler has a gas line of 2
double solenoids the diagnostics will indicate which solenoid of
the double solenoid is at fault.
The last fault instruction will be retained.
FAULT CODES
Fault codes numbered 1 to 24 are displayed where applicable.
In this event contact Caradon Plumbing Limited.
WARNING.
The ON/STANDBY [1/0] button does NOT electrically
isolate the boiler.
Before attempting any electrical fault finding ALWAYS carry out
the preliminary electrical system checks, as detailed in the
Instructions for the British Gas Multimeter or other similar
commercially available meter.
The preliminary electrical system checks are the FIRST
electrical checks to be carried out during a fault finding
procedure.
On completion of any service / fault finding task which has
required the breaking and remaking of electrical connections
the following checks MUST be repeated:
a. Earth continuity
b. Polarity
c. Resistance to earth
Detailed instructions on the replacement of faulty components
are contained in the 'Servicing' section of these Installation &
Servicing Instructions.
GENERAL INFORMATION
If a flow switch is not connected to the boiler a link should be
fitted between the 2 terminals for the flow switch. If the
terminals are left disconnected the display will indicate "No
flow" and the boiler will not operate.
Anti-cycle will be in operation each time the boiler thermostat is
satisfied and a rapid demand for heat is required. The same
situation will occur if the external controls operate rapidly. This
feature reduces component wear and ensures continuous
trouble-free operation. The Anti-cycle duration is 1 to 3
minutes.
If the system pump, with a maximum current of 3A, is
connected to the boiler pump terminals, pump overrun will be
in operation if the flow temperature is greater than 75
o
C when
the heat demand is satisfied and will continue to run until the
boiler flow is less than 75
o
C. If the flow temperature is less
than 75
o
C when the demand for heat is satisfied the pump will
cease to operate.
Frost protection is inbuilt with the boiler. If the flow temperature
falls to approximately 3
o
C then the boiler will operate until the
flow temperature exceeds 4
o
C. If an external frost thermostat
is required the internal programmer should be set to [24 hours]
under the programme status menu and an external
programmer and frost thermostat wired and connected to the
volt-free external control terminals on the boiler.
There is an option kit available with 2 sets of volt-free contacts.
1 set of volt-free contacts is for "Lockout" and "Overheat"
combined and 1 set of volt free contacts is for "Boiler run".
There is an option kit available to enable temperature
compensation to be used. The outside temperature adjusts the
boiler flow temperature to satisfy the heating load and ensure
efficient boiler operation.
The gas valves operate on a High/Low and Off principle. At
start up, with the flow temperature less than 55°C, the boiler
will start at low rate and, after 1 to 3 minutes, the high rate gas
valves will open. On reaching the set point, determined by the
FAULT FINDING
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