MGN 2800N HP 18
Gas Supply Pressure
The main gas safety valve is capable of withstanding gas inlet pressures up to 200 mbar. For MGN
2800N
HP burners it is essential that the inlet gas pressure shall not be less than 45 mbar and not be more
than 100 mbar in order to maintain good control characteristics of the air/gas ratio controller. Before
proceeding with commissioning:
a. Fit a manometer or other approved pressure measuring instrument to the pressure test point on
the upstream side of the first safety shut-off valve.
b. Open the manual gas isolation valve at the inlet to the gas train.
c. Check that the gas pressure is adequate.
ESTABLISHING MAIN FLAME
General Notes
In the following sections, reference is made to checking gas flow rates at the gas meter. This is the
most accurate method of determining throughputs and should always be used whenever possible.
Information regarding the burner head gas pressures is included in the appendix at the back of this
manual. These may be used as a guide to initial burner settings, but should not be relied upon to
offer proof of actual throughputs.
IMPORTANT
-
after each adjustment, gas flow rate and flue gas analysis should be checked.
ALWAYS
-
use approved test equipment.
NEVER
-
rely on a visual inspection of the flame as a guide to combustion quality.
Landis & Staefa SKP75
Refer to the
Valve Adjustment Diagram
on page 12. Set up the air damper for initial firings as
follows.
Low Flame air 15°; High Flame air 60°. Close the upstream manual valve until it reaches an opening
of approximately 20%.
Set the gas inlet pressure switch to minimum. Remove the low flame check link. Switch the burner
on and allow it to establish low flame. Gradually open the upstream manual valve to the fully open
position keeping a watchful eye on the CO level.
If the CO content is excessive, adjust the low fire adjustment screw (2) on the SKP75 valve to
achieve acceptable figures. In extreme cases it is possible to run out of adjustment on the low fire
screw without achieving the desired results. If this happens adjust the High Fire setting screw (1) to
bring the CO content down to an acceptable level.
Switch the burner off and refit the low flame link. Restart the burner. Low flame will be established,
expanding to main flame after the expiry of period T6 on the control box timing chart.
It is important to monitor the flame visually during the change from low to high. If the flame becomes
more compact, this indicates an excess of combustion air. If the flame becomes large and
shapeless, this indicates an excess of fuel. Both conditions are acceptable at this stage providing
that the burner remains stable and immediate actions are taken to correct the situation. If in doubt
SWITCH OFF the burner and adjust the High Flame screw (1) on the SKP75 in the appropriate
direction.
With the burner stable on high flame, adjust the High Flame screw (1) to bring the CO
2
to an
acceptable level. It is possible at this stage that the burner may be overfiring the appliance with a
resultant excess of CO.
With the burner firing at low flame, adjust the Low Flame screw (2) on the SKP75 valve to bring the
CO
2
content within an acceptable range.
Adjustment of the Low Flame setting will have marginal effect on High Flame. To achieve optimal
results repeat the above procedures on High and Low flame several times until acceptable figures are
obtained without any further adjustment.
It should not be necessary to make any further adjustments to the gas valve.
