Keston K130 Installation And Servicing Instructions page 26

WD52/0/1997
the gas inlet pressure is satisfactory
remove the brass dust cap covering the
burner pressure adjustment screw on the
gas valve (See fig. 4.7). Set the gas
pressure to the required value as stated
on the databadge by turning the exposed
burner pressure adjustment screw
(clockwise will increase burner pressure,
anti-clockwise will decrease burner
pressure). This will ensure that
combustion is good enough to allow
combustion fine tuning to take place.
Replace the brass dust cap to cover the
burner pressure adjustment screw.
4.8 TIMING THE GAS METER -
NATURAL GAS
After the boiler has been started, and 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 3% of the rated input.
Time, in seconds, the time taken to pass 2 cubic feet of gas through the meter (ie one
revolution of a 2 cu ft dial) or 0.1 cubic metres if the meter is of the new metric digital type.
The Keston 130, when correctly set, should take 51.8 seconds for 2 cubic feet of natural
gas and 91.5 seconds for 0.1 cubic metres of natural gas (assuming 1038 btu/h per cubic
foot). Adjust the gas valve screw clockwise to increase the input (speed up the meter) or
anticlockwise to decrease the input (slow down the meter) accordingly.
4.9 COMBUSTION FINE TUNING
Although the gas pressure is preset at the factory differing flue arrangements may require
fine tuning of the gas pressures to produce the best combustion and ensure long burner
life. It is advisable to check proper combustion by measuring gas input and the level of
carbon dioxide, or oxygen, in the flue outlet from the boiler. Overfiring or underfiring the
burner will reduce the longevity of the appliance.
Carbon dioxide is a colourless, odourless gas produced by all combustion processes.
When the Keston condensing boiler is operating properly carbon dioxide (CO
be between 8.2 and 8.9% CO2 for natural gas.
To measure CO2 levels in the Keston boiler remove the 1/8" plug from the flue outlet pipe
inside the boiler (Figure 5.7.2 item 69). Insert the probe of a combustion analysis meter
and sample the gases as instructed in the test equipment's instructions.
If the CO2 levels need raising increase the gas output by turning the brass screw, under
the metal cap in the front of the gas valve, clockwise. Reduce CO2 levels by turning this
screw anti-clockwise.
If CO2 levels do not respond to adjustments the burner is probably running with too much
gas pressure. If, for instance, a clockwise adjustment to the brass screw in the gas valve
produces a decrease in CO2 the burner is too fuel-rich and not enough oxygen is present
for proper and complete combustion
Installation & Servicing Instructions
Chapter 4 : Commissioning
Burner pressure
Adjustment
Burner pressure
test nipple.
.
The Keston 130 Condensing Boiler
Fig 4.7
GAS VALVE
) levels will
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