Publication No. 5106226
42
Powermax
-
+
SEL
SEL
-
+
MAIN
S ON
POW
ER
CH
HW
PRO
G
PROG
C.H. A
DVAN
CE
H.W. TE
MP
RESET
BUR
NER
LOC
K OU
T
Air/Gas
Valve
Flue Gas
Test Point
Air
Manifold
Venturi
Fan
Venturi
Connector
Air Manifold
MAX0031B
Air/Gas
Ratio Valve
Top View
Inlet Pressure
Test Point
Outlet Pressure
Test Point
Condensate Vent
(
Do Not
disturb this vent tube)
Signal sensing tube
connected to Gas Valve
Tee inserted
into signal
sensing tube
Air Signal
Connection
Offset
Adjustment
Do Not
use
this point
Throttle
Adjustment
Manometer
MANOMETER
P200UL
0.0
UNIT
V
V
AUTO
HOLD
Fig. 28
Gas/Air Valve Setup Procedure
Gas/Air Valve Setup Procedure
Procedure to correctly set new Air/Gas Valve
using a micro-manometer.
1. Loosen screw in outlet pressure test point
and connect to ‘+’ (positive) side of
differential micro-manometer.
Tee the ‘-’ (negative) side of the micro-
manometer into the air signal tube.
2. Remove special ⁄ BSP screw from flue
gas outlet (above heat exchanger) and
insert probe of combustion analyser
approximately 50 mm.
Temporarily seal probe into flue gas test
point.
3. Press ‘ADVANCE’ or central heating
‘SELECT’ button to obtain ON display in
programmer screen. Ensure any
connected room thermostat is calling for
heat. Observe burner lights and allow
boiler to operate in central heating mode
for several minutes.
4. Simultaneously press ‘+’ and ‘STEP’
buttons and hold down for 5 to 6 seconds.
After one minute, the boiler will be
operating at the correct reduced input rate
to enable the differential pressure to be set.
5. Ensure micro-manometer is in Pa or mbar
scale and has zeroed correctly. If in doubt,
re-zero the instrument.
6. Check differential pressure reading.
This should be zero or a negative (gas
relative to signal) value of 0 to - 5 Pa (0.00
to - 0.05 mbar).
Use zero adjustment screw (below central
dust cover) to reset differential if
necessary.
Note:
Turning adjustment screw clockwise
reduces negative differential; anti-
clockwise increases negative differential. A
4 mm hexagon key should be used to make
the adjustment.