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FAULT FINDING
FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING
30
Concord CXSi/H - Installation & Servicing
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
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
40
BOILER CONTROL
feature reduces component wear and ensures continuous
trouble free operation. The anti-cycle duration is 4 minutes.
If the system pump, with a maximum current of 3A, is
connected to the boiler pump terminals, pump overrun will be
in operation when the demand for heat is satisfied, and will
continue to run for 6 minutes.
Frost protection is inbuilt with the boiler. If the flow
temperature falls to approximately 5
o
C then the boiler will
operate until the flow temperature exceeds 18
o
C. Note that it
is designed to protect the boiler and may not protect remote
parts of the system. Neither the pump overrun nor the inbuilt
frost protection will operate if the boiler thermostat is switched
OFF.
The gas valves operate on High/Low and Off principle. The
boiler will start at low rate and after 1 minute the high rate gas
valve will open. On reaching the set point, determined by the
user, the boiler will go to low rate and when the temperature
reaches the set point plus 3
o
C the low rate gas valve will
close. Should the temperature fall below the set point the
boiler will go back to the high rate.
The full sequence control enables a single ignition attempt
lasting about 5 seconds and will go to lockout if detection
does not take place.
41
SIMPLE FLOW CHART
OF OPERATION
SHUTDOWN
IGNITION
LOW RATE
HIGH RATE
Flame = ON
PUMP OVERRUN
(6 minutes)
Temp at
set point
Overrun
completed
Demand = ON
Temp
> than
set point
4 minutes anti-cycle
Demand
= off
157294-3.pmd 11/8/2005, 9:59 AM30