Recommended Combustion Test Sequence - Beckett CG25 Manual

.
.
High gas pressure switch - With the burner firing
and a manometer attached to the test port nearest
the high pressure switch, gradually increase the
gas pressure until the high pressure switch opens
and shuts the burner off. Note the pressure and
manually reset the switch. The high gas pressure
switch should be set at one and one half times the
high fire manifold pressure (see nameplate data in
Figure 1 or set switch as determined by testing).
Leak-test valve - With the burner firing and ma-
nometer attached to the leak-test valve port, turn
the burner electrical switch off and observe that
the gas pressure does not increase after several
minutes. This proves total closure of the main gas
valve.
.
.
Flame safeguard safety lockout - Simulate a
flame failure by turning the main gas supply off.
The control should shut the burner off on safety
within the safety lockout time.
Flame sensor circuit (flame rod) - With the
burner power switch turned off, refer to the wiring
diagram supplied with the control and locate the
sensor connection terminals. Place DC voltmeter
probes in the flame amplifier test jacks. With the
burner firing, the flame signal should be steady and
at least 1.25 VDC.
10. Flame sensor
circuit (UV scanner) - With the
burner power switch turned off, refer to the wiring
diagram supplied with the control and locate the
sensor connection terminals. Place DC voltmeter
probes in the flame amplifier test jacks. With the
burner firing, the flame signal should be steady and
at least 1.25 VDC.
Use test instruments to set combustion:
Always use calibrated test instruments to set combustion
levels. Verify that test instruments are calibrated and in
good working condition. If not already provided, drill test
access holes in the flue pipe near the breech (or upstream
of the boiler breech damper, if applicable) and in the front
mounting plate area for firebox pressure. Be careful not
to damage any water-backed surface.
Verify that all boiler sections, canopy, and access plates or
doors are fully equipped with gaskets and sealed against
any leakage, which could affect the combustion test re-
sults. Before making these tests, operate the burner for
several minutes to allow the heating system temperature
to stabilize or nearly reach steady-state levels. Record all
results
CI
CI
CI
CI
in the start-up log for future reference.
Draft - Set the breech or furnace pressure to the
level specified by the appliance manufacturer.
Typical example: +0.10" W. C.
Oxygen - It is recommended that you measure
the oxygen (02) early in the test sequence be-
cause high levels of carbon monoxide can be cre-
ated at very low or even very high 02 levels. The
typical operating range is between 2.5% - 4.5 %.
The equivalent carbon dioxide (CO2) operating
range is 9% - 10.5%.
Carbon monoxide (CO) -An operating range of
0 -50 PPM is recommended for the burner. The
maximum carbon monoxide (CO)level permitted
in the flue gas by the UL 795 Standard is 400 PPM
(0.04%).
Stack Temperature - The stack temperature
should be within the range specified by the appli-
ance manufacturer. It is influenced by input firing
rate, flame shape, excess air ratio, and cleanli-
ness of boiler flue passages. This temperature,
combined with the ambient temperature, and
02% (or CO2) is used in calculating the appliance
efficiency.
Recommended combustion test sequence:
1. Adjust the draft or breech pressure to the appli-
ance manufacturer's recommended level.
2. Measure the carbon monoxide level and adjust
air settings, if necessary, to regulate it to about 50
PPM for a starting point.
3. Measure the 02 or CO2 at the 50 PPM CO level.
For this discussion, assume the 02 is 1.5% (11%
CO2).
.
Open the air adjustment until the 02 level is in-
creased by at least 1% or to 3% 02 (whichever
is higher). This should reduce the CO level and
provide a margin of reserve air to accommodate
variable conditions.
5. Sample the CO level again. It should be in the 0
to 20 PPM range.
6. Check the draft to ensure it still meets specifica-
tions. If a major change in draft is required, re-
peat the above steps.
.
Perform any final adjustments and lock the air
settings securely. Run the burner through several
cycles to verify prompt ignition and stable burner
operation.
24, 6104 80G50 RoB