Keston 50 - GC Installation And Servicing Instructions page 27

WD50/0/1996
d. Turn on the electrical supply, setting any external controls to call for heat.
e. ON/OFF switch - select 'ON'. The amber 'run' light will illuminate on the ON/OFF
switch, the red 'lockout' light will illuminate, the blower and pump will start and,
after about 15 seconds, a spark will attempt to light gas at the burner. With the
gas service cock off, the boiler will go to lockout - red light illuminated, but the
blower and pump will continue to run. At intervals of approximately 1 minute the
boiler will make two further attempts to fire. After the final attempt the blower will
run for a further 20 seconds before shutting down.
f. Vent the water system.
Important:
The Keston heat exchanger consists of a single coil which can trap an air pocket.
Great care must be taken to ensure that water flow has been established through
the heat exchanger and thus ensuring no air pockets remain in the heat
exchanger and pipe work. Firing the boiler while an air pocket exists in the heat
exchanger could damage it.
g. Note the reading on the pressure gauge caused by the suction of the blower. This
should be approximately minus 12 mbar for the Keston 80, minus 26 mbar for the
Keston 60 and minus 32mbar for the Keston 50. If it is not, check the system as
follows:
If the negative pressure exceeds the required figure, then it suggests
that there is a possible restriction in the air inlet pipework.
If the negative pressure is less than required figure, then it suggests
that there is a possible restriction in the flue outlet pipework. Note the
exact reading.
h. Turn the gas service cock to ON.
i. Turn off the electricity supply, wait 10 seconds and turn back on. The boiler will
again go through its ignition sequence but this time the main burner will light,
provided all air has been purged from the gas supply to the boiler. When the
burner is lit and the boiler is operating normally the the green (run) lamp, the
upper lamp adjacent to the flame symbol, will also be illuminated indicating
successful ignition.(If it does not, air is indicated - turn off and repeat the
procedure).
If this does not occur, the green (run) lamp, the upper lamp adjacent to the flame
symbol, will be extinguished and, at approximately 1 minute intervals, the
electronic ignition system will make two further attempts to light the burner.
If the ignition is successful and the boiler is operating normally, the green (run)
lamp, the upper lamp adjacent to the flame symbol, and the red (lockout) lamp will
be illuminated simultaneously.
If, after three automatic attempts, the boiler still fails to ignite, the green (run)
lamp, the upper lamp adjacent to the flame symbol, will be extinguished and the
red (lockout) lamp will remain illuminated.
If, after five manual attempts (to allow for purging of any air in the gas line), the
boiler still fails to ignite (indicated by the red (lockout) lamp) refer to Section 5.2 -
Fault Finding Flow Chart.
j. Check for gas soundness between the gas service cock and connection to the
burner manifold.
Installation & Servicing Instructions
Chapter 4 : Commissioning
Page : 24
The Keston 50, 60 & 80 Condensing Boilers