6) Using the “+” button for CH
temperature control, adjust the
display back to “t99” and check
the CO
2
level is in the range
indicated at point 3)
5.8 CHECKING THE GAS PRESSURE
NB: It is advisable to carry out this
test with the user control knob turned to
maximum and the system water cold to
ensure the boiler is running at
maximum rate.
The gas setting is factory adjusted to
within the required range and should
not need adjustment. If the reading is
incorrect then check such factors as
soundness of the air and flue pipe
joints and the gas inlet pressure (pos.
3) (minimum 18 mbar required for natural gas, minimum 31 mbar required for LP gas).
If all joints are sound and the gas inlet pressure is satisfactory check the gas input
by timing the gas meter as detail in Section 5.9 Timing The Gas Meter.
If the gas
input cannot be measured then it’s compulsory to measure the combustion quality
as detail in Section 5.7 Combustion Testing.
5.9 TIMING THE GAS METER
Set the boiler DHW temperature to 65C and open two hot taps in the property fully. With
no other appliances using gas, time the gas meter to be certain that the unit is running at
the proper gas input. Determine the cubic feet of gas passing through the meter and
determine the input in Btu per hour. Input must be within plus or minus 5% of the rated
input.
Time, in seconds, the time taken to pass 2 cubic feet of gas through the meter (i.e. one
revolution of a 2 cu ft dial) or 0.1 cubic metres if the meter is of the new metric digital type.
Model Time for 2 cu ft Time for 0.1 cu m
C36 Combi (natural gas) 54 95
C36P Combi (LPG) 141 249
If the meter timing is found to be incorrect when the boiler is firing at maximum rate
contact Keston Boilers Ltd for further guidance.
5.10 HANDING OVER TO THE USER
It is important to fully explain the following:
a. Procedure to light and turn off the boiler, including isolation of the electrical supply
if necessary.
b. The function of the lockout feature must be explained :
If the display shows “E 01” this means that the boiler has failed to light. Press the
“Reset” button and wait.
i) If lockout recurs immediately then the gas supply should be checked as
ON, otherwise consult a Service Engineer.
ii) If it is not possible to relight, the boiler must be isolated and a Service
Engineer called in to rectify the fault.
c. Advise that a reduction in the water pressure reading on the system pressure
gauge, for sealed systems, indicates a leak which should be rectified before
further use.
d. Advise that the appliance should be serviced by a competent person at least once
a year.
Complete all sections of the Chapter 10 Gas Boiler Commissioning Checklist that are
relevant to the appliance installation. The details will be required in the event of any
warranty work.
e. Advise on the frost protection and pump/fan exercise feature.
f. Advise the user that a plume of water vapour (steam) from the flue terminal is
normal and that there is no need for concern.
WD388/0/2004 Chapter 5 : Commissioning The Keston C36 Combi & C36P Combi Boilers
Installation & Servicing Instructions Page : 24
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