29
Concord CXS -
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
41 BOILER CONTROL
F
AUL
T FINDING
FAULT FINDING
F
AUL
T FINDING
rapidly. This 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 3 minutes 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.
42 SIMPLE FLOW CHART
OF OPERATION
SHUTDOWN
IGNITION
LOW RATE
HIGH RATE
Flame = ON
PUMP OVERRUN
(6 minutes)
Temp at
set point
Flame = ON
(3 minutes Low rate)
Overrun
completed
Demand = ON
Temp
> than
set point
4 minutes anti-cycle
Demand
= off
