Setting Main Flame Rates and Air/Gas Ratios
From this point the gas commissioning process is concerned with setting the main and start gas flow
rates to appropriate values and ensuring that the combustion quality of the system is within
acceptable limits. During this process:
AFTER EACH ADJUSTMENT check the flue gas analysis and gas flow rate.
ALWAYS use approved and calibrated test equipment.
NEVER rely on visual observation of the flame as the only guide to combustion quality.
1.
Fit a manometer or other approved pressure measuring instrument to the gas pressure test
point nearest to the burner head. The relationship between the pressure at this point and
burner heat input is shown in the graphs in the Appendix. This information is provided only as a
guide and it should not be used in conjunction with pressure measurements as a substitute for
accurate measurement of gas flow rate, for example, a gas meter.
2.
Ensure that the flue gas analysis equipment is functioning.
3.
Close the manual gas isolation valve at the inlet to the gas train to an opening of approximately
20%.
4.
Set the gas inlet pressure switch to its minimum value.
5.
With the burner set for low flame hold (hand operation), re-establish the electrical supply and
switch on the burner.
6.
The burner controller will run through its sequence, initiating the ignition spark and opening the
start gas safety shut-off valve. The start gas flame will be established and the UV cell will begin
monitoring.
7.
The main gas control valve will open and low fire will be established. Open the upstream
manual valve slowly until it is fully open, observing the CO level.
8.
If the CO level is too high (see below) reset the low fire adjusting screw (2) on the air/gas ratio
controller (refer to the diagram on page 13) until an acceptable figure is achieved. In extreme
cases the adjustment on screw (2) may be exhausted without achieving an acceptable CO level.
In this event, reset the high fire adjusting screw (1) until an acceptable CO level is achieved.
9.
Confirm the leak tightness of the pipework downstream of the main gas safety shut-off valve
using a proprietary detection fluid.
10. Switch off the burner and the electrical power supply to the burner.
11. Open the control panel cover and switch the burner from low flame hold to normal run position.
On modulating and sliding high/low burners select the ‘Auto’ position of the Hand/Auto switch.
Close the cover.
12. Establish the electrical supply to the burner and switch on the burner. The burner controller will
run through its sequence. Low fire will be established, expanding to main flame. Monitor the
flame visually during the transition from low to high fire. If the flame becomes more intense and
compact this indicates an excess of combustion air. If the flame becomes too large and
shapeless, this indicates an excess of fuel. Either condition is acceptable at this stage provided
that the flame is stable and the commissioning process continues immediately. If in doubt,
switch off the burner and adjust screw (1) on the air/gas ratio controller appropriately before
restarting the burner.
13. With the burner running on high fire, measure the flue CO
2
level and adjust screw (1) to bring
the level to an acceptable level. Note that at this stage the burner may be overfiring the
appliance and producing excessively high levels of CO. Check the level of O
2
to confirm the
CO
2
reading.
14. Set the burner for low flame and hold (‘Hand’ operation) and switch on the burner. Allow the
burner controller to run through its cycle until the burner is running on low fire.
15. Adjust the low fire adjusting screw (2) to bring the CO
2
level to an acceptable level.
MDFL 3300 & MDFL 4000 Issue 2 08/08
Page 32
Summary of Contents for MDFL 3300
Page 16: ...MDFL 3300 MDFL 4000 Issue 2 08 08 Page 15 VALVE PROVING SYSTEM LDU 11 Standard fitting...
Page 30: ...MDFL 3300 MDFL 4000 Issue 2 08 08 Page 29 MODULATING CAM BOX...
Page 43: ...Electrode Setting Details MDFL 3300 MDFL 4000 Issue 2 08 08 Page 42 All dimensions in mm...
Page 48: ...NOTES MDFL 3300 MDFL 4000 Issue 2 08 08 Page 47...