Use Test Instruments To Set Combustion; Recommended Combustion Test Sequence - Beckett CG15 Manual

6. High gas pressure switch – With the burner fi ring
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 fi re
manifold pressure (see nameplate data in Figure 1
or set switch as determined by testing).
7. Leak-test valve – With the burner fi ring and
manometer 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.
8. Flame safeguard safety lockout – Simulate a fl ame
failure by turning the main gas supply off. The control
should shut the burner off on safety within the safety
lockout time.
9. 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 fl ame amplifi er test jacks. With the
burner fi ring, the fl ame signal should be steady and
at least 1.25 VDC.

Use Test Instruments to Set Combustion

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
results. 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 in the start-up log for future reference.
Draft – Set the breech or furnace pressure to the level
specifi ed by the appliance manufacturer. Typical example:
+0.10" W. C.
Always
instruments
levels. Verify that test instruments are calibrated and in
good working condition. If not already provided, drill test
access holes in the fl ue pipe near the breech (or upstream
of the boiler breech damper, if applicable) and in the front
mounting plate area for fi rebox pressure. Be careful not
to damage any water-backed surface.
CG15, CG25, CG50 Burner Manual
use calibrated test
to set combustion
Oxygen – For both low fi re and high fi re it is recommended
that you measure the oxygen (O 2 ) early in the test
sequence because high levels of carbon monoxide can
be created at very low or even very high O 2 levels. The
typical operating range is between 2.5% – 4.5 %. The
equivalent carbon dioxide (CO 2 ) operating range is 9%
– 10.5%.
High excess air levels reduce the
fl ame's UV output and the scanner
signal that proves the burner is fi ring.
Carbon monoxide (CO) – An operating range of 0 -
50 PPM is recommended for the burner. The maximum
carbon monoxide (CO) level permitted in the fl ue gas by
the UL 795 Standard is 400 PPM (0.04%).
Stack Temperature – The stack temperature should be
within the range specifi ed by the appliance manufacturer.
It is infl uenced by input fi ring rate, fl ame shape, excess
air ratio, and cleanliness of boiler fl ue passages. This
temperature, combined with the ambient temperature,
and O 2 % (or CO 2 ) is used in calculating the appliance
effi ciency.

Recommended Combustion Test Sequence

1. Adjust the draft or breech pressure to the appliance
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 O 2 or CO 2 at the 50 PPM CO level.
For this discussion, assume the O 2 is 1.5% (11%
CO 2 ).
4. Open the air adjustment until the O 2 level is increased
by at least 1% or to 3% O 2 (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 specifi cations.
If a major change in draft is required, repeat the
above steps.
7. Perform any fi nal adjustments and lock the air
settings securely. Run the burner through several
cycles to verify prompt ignition and stable burner
operation.
Section: Start the Burner
27