Potterton 7668920, Engineer'S Service Manual

Page: 10 / 20

10
EV1
EV2
P. OUT
1 2 3 4
VENT
RQ ADJ.
P.
R.A
DJ.
‘A’
Max Rate
Adjustment
Screw
(cover removed)
‘B’
MIN rate
Adjustment
Screw
(cap fitted)
Reduce CO
2
at MIN. rate
Increase CO
Increase CO
2
at MIN. rate
Reduce CO
2
at MAX. rate
2
at MAX. rate
7.0 Setting and checking the air/gas ratio
7.1 Setting the boiler to full load & part load
Use this procedure when Commissioning, Servicing &
Replacing the Gas valve.
The full load status can only be reached via the part load
status.
1. Press the Chimney Sweep button for around 3 seconds.
The status signal for the Chimney Sweep button is orange
and flashes green briefly; Part load is selected.
2. Press the Chimney Sweep button again twice. The
status signal for the Chimney Sweep button is orange and
goes off briefly twice; Full load is selected.
3. Remove the plug of the flue gas measurement point.
4. Insert the probe for the flue gas analyser into the
measurement opening. See Fig for the position of control
screw A for full load adjustment.
5. Check the CO
2
is 9.3% ±0.1% (Case OFF). If the CO
2
is
too low, turn the screw A anticlockwise to increase (2.5mm
Allen key). If the CO
2
is too high, turn the screw A clock-
wise to decrease. Now part load needs to be selected
6. Press the Chimney Sweep button again to return to part
load. The status signal for the Chimney Sweep button is
orange and flashes green briefly; Part load is selected.
See drawing for the position of control screw B for part
load.
7. Check the CO
2
is 8.9% ± 0.1% (Case OFF). If the CO
2
is too high, turn the screw B anticlockwise to reduce (4mm
Allen key). If CO
2
is too low, turn the screw B clockwise to
increase.
8. Briefly press the RESET button to return the boiler to
normal operating status.
9. Remove the probe for the flue gas analyser from the
measurement opening.
10. Refit the plug of the flue gas measurement point.
WARNING!
The full load value must be at least 0.4%
higher than the part load value. If this gap
has not been achieved the values must be
reset.
Plug
Analyser Probe
Flue Sampling
Point
After refitting the sampling
point plug ensure there is
no leakage of products !