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Pressure Test
Point Screw
Fig. 35
NAC
Modulator
Feed Wires
Fig. 36
Gas Valve
Modulator
Cover
Fig. 36a
(NAC removed
for clarity)
Central Heating and
Domestic Hot Water
Position
30° 40° 50° 60° 70° 80°
Selector
Central Heating
Switch
Temperature Control
Fig. 37
24
Gas Valve
(NAC removed
for clarity)
Hot Water
Temperature Control
9.0
9.2
1. Turn on the gas and electrical supplies to the
boiler and ensure that all external controls are
calling for heat.
2. Set the hot water temperature control to
maximum and the selector switch to the OFF
position (Fig. 37).
3. Slacken the pressure test point sealing screw
and connect a pressure gauge. Disconnect the
sensing pipe from the spigot adjacent to the
pressure test point (Fig. 35).
4. Turn the selector switch fully anticlockwise
against the spring pressure to position R and hold
for 2 seconds to reset the boiler.
5. Turn the selector switch to the Domestic Hot
Water position and open a hot water tap to give a
flow rate of at least 10l/min.
6. Remove the plastic cap and using a suitable
spanner adjust the brass nut to give a maximum
output setting pressure of 10.6 mbar (Fig. 36).
7. Disconnect one of the modulator wires from the
gas valve. Adjust the red screw to achieve the
correct minimum output setting pressure of 1.9
mbar (Fig. 36a).
8. Turn the boiler off and reassemble in reverse
order. Tighten the pressure test point sealing
screw and reconnect the sensing pipe.
9. The system should then be flushed again in
accordance with BS 7593 and the flushing agent
or inhibitor manufacturers instructions.
2
bar
Commissioning the Boiler
Checking the Burner Pressure
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