18
Mynute 24m
7.1
CHECKING APPLIANCE OPERATION
When carrying out any repairs or servicing to the
appliance, the relevant commissioning procedure
must be undertaken to ensure the continued safe
operation of the appliance. Particular attention should
be made to ensure gas soundness, water sound-
ness and the electrical integrity of the appliance.
7.2
APPLIANCE MODE OF OPERATION
When there is a request for heat and/or hot water
via the programmer/time clock and/or any external
control, the pump and fan are started.
NOTE
There must be sufficient system water pressure
(min. 0.5 BAR) to ensure the water pressure
switch is activated. If there is insufficient system
pressure the pump and fan will be prevented from
operating. When the fan runs, it proves the differ-
ential air pressure switch which in-turn allows an
ignition sequence to begin.
NOTE
The ignition sequence lasts approximately 5 sec-
onds, during which the appliance will continue to
spark even if the burner has already lit. If the
spark/sensing electrode does not sense ignition
the appliance will then go to lockout. Ignition is
sensed by the electronic circuitry to ensure flame
stability at the burner. Once successful ignition
has been achieved, the electronic circuitry allows
75% 0f the full gas rate through the appliance.
After 15 minutes the gas rate is increased to
maximum (100%). When the appliance reaches
the desired temperature the burner will shut down
and the boiler will perform a three-minute anti-
cycle (timer delay).
NOTE
The timer delay can be de-activated by the inser-
tion of a “jumper” on the PCB or by isolating the
appliance from the electrical supply for 30 sec-
onds. When the request for heat and/or hot water
has been satisfied, the appliance pump and/or fan,
may continue to circulate to dissipate any residual
heat within the appliance.
7.3
CHECKING AND ADJUSTING BURNER
PRESSURE (fig. 17)
Although the burner pressure is factory set, it is
necessary to check it during servicing or if the gas
valve has been removed. Isolate the appliance
from the electrical supply and attach a suitable
manometer to the gas valve outlet test nipple.
Remove the compensator tube.
7.3.1
SETTING THE MAXIMUM BURNER PRES-
SURE
Light the boiler as described in 5.6 and compare
the reading on the manometer with the value
described in 2.2. If adjustment is required, remove
the protective cap from the gas valve modulating
coil assembly and turn the outer (10mm) nut
clockwise to increase, or counter-clockwise to
decrease the burner pressure.
SECTION 7 CHECKS, ADJUSTMENTS AND FAULT FINDING
NOTE
You should ensure that all radiators or heat emit-
ters are fully open during the above procedure.
This will ensure that the output of the boiler (burner
pressure) is not compromised due to a high flow
temperature.
7.3.2
SETTING THE MINIMUM BURNER PRESSURE
Once the maximum burner pressure has been
checked and/or adjusted, remove one of the grey
wires from the modulating coil. Compare the read-
ing on the manometer with the value described in
2.2. If adjustment is required, turn the inner (red)
cross-head screw clockwise to increase, or coun-
ter-clockwise to decrease the burner pressure,
whilst ensuring that the outer (10mm) nut does not
move.
When checking and/or adjustment has been
completed, isolate the appliance from the
electrical supply, replace the protective cap, refit
the compensator tube, refit the grey wire to the
modulating coil, remove the manometer and
tighten the outlet test nipple.
IMPORTANT
A GAS SOUNDNESS CHECK MUST BE CAR-
RIED OUT.
7.4
COMBUSTION ANALYSIS TEST
A combustion analysis check can easily be car-
ried out on the appliance via the test points located
on the top of the appliance, however you must
check that the burner pressures are set correctly
(see section 7.3).
•••••
Insert the flue gas analyser probe into the right
hand test point (see fig 25).
•
Locate and remove the protective cap that
conceals the “CO mode” button (see fig. 25A).
•
Light the boiler as described in 5.6 and press
the “CO mode” button once.
•
The boiler will now enter the combustion analy-
sis mode (CO mode) for a period of 15 minutes.
During this time it will remain on full gas and ‘CO’
will be displayed on the LED display
.
•
Once the flue gas analysis has been made,
press the “CO mode” to resume normal opera-
tion.
Fig. 18
flue gas
test point