Beckett CG50, CG25 Recommended Combustion Test Sequence, Use Test Instruments to Set Combustion

			Section: Start the Burner
6. High gas pressure switch – With the burner firing		Oxygen – For both low fire and high fire it is
and a manometer attached to the test port nearest		recommended that you measure the oxygen (O2) early
the high pressure switch, gradually increase the		in the test sequence because high levels of carbon
gas pressure until the high pressure switch opens		monoxide can be created at very low or even very high
		O2 levels. The typical operating range is between 2.5%
and shuts the burner off. Note the pressure and
		– 4.5 %. The equivalent carbon dioxide (CO2) operating
manually reset the switch. The high gas pressure		range is 9% – 10.5%.
switch should be set at one and one half times the			High excess air levels reduce the
high fire manifold pressure (see nameplate data in
			flame’s UV output and the scanner
Figure 1 or set switch as determined by testing).
		signal that proves the burner is firing.
7. Leak-test valve – With the burner firing and		Carbon monoxide (CO) – An operating range of 0 -50
manometer attached to the leak-test valve port, turn
		PPM is recommended for the burner. The maximum
the burner electrical switch off and observe that
		carbon monoxide (CO) level permitted in the flue gas by
the gas pressure does not increase after several		the UL 795 Standard is 400 PPM (0.04%).
minutes. This proves total closure of the main gas		Stack Temperature – The stack temperature should be
valve.
8. Flame safeguard safety lockout – Simulate a		within the range specified by the appliance manufacturer.
		It is influenced by input firing rate, flame shape, excess
flame failure by turning the main gas supply off. The		air ratio, and cleanliness of boiler flue passages. This
control should shut the burner off on safety within		temperature, combined with the ambient temperature,
		and O2% (or CO2) is used in calculating the appliance
the safety lockout time.
		efficiency.
9. Flame sensor circuit (flame rod) – With the
burner power switch turned off, refer to the wiring		Recommended Combustion Test Sequence
diagram supplied with the control and locate the
sensor connection terminals. Place DC voltmeter		1. Adjust the draft or breech pressure to the appliance
probes in the flame amplifier test jacks. With the		manufacturer’s recommended level.
burner firing, the flame signal should be steady and		2. Measure the carbon monoxide level and adjust
at least 1.25 VDC.
		air settings, if necessary, to regulate it to about 50
10.Flame sensor circuit (UV scanner) – With the
		PPM for a starting point.
burner power switch turned off, refer to the wiring		3. Measure the O2 or CO2 at the 50 PPM CO level.
diagram supplied with the control and locate the
sensor connection terminals. Place DC voltmeter		For this discussion, assume the O2 is 1.5% (11%
probes in the flame amplifier test jacks. With the		CO2).
burner firing, the flame signal should be steady and		4. Open the air adjustment until the O2 level is
at least 1.25 VDC.		increased by at least 1% or to 3% O2 (whichever
		is higher). This should reduce the CO level and
Use Test Instruments to Set Combustion		provide a margin of reserve air to accommodate
		variable conditions.
Verify that all boiler sections, canopy, and access plates		5. Sample the CO level again. It should be in the 0 to
		20 PPM range.
or doors are fully equipped with gaskets and sealed
		6. Check the draft to ensure it still meets
against any leakage, which could affect the combustion
test results. Before making these tests, operate the		specifications. If a major change in draft is
burner for several minutes to allow the heating system		required, repeat the above steps.
temperature to stabilize or nearly reach steady-state		7. Perform any final adjustments and lock the air
levels. Record all results in the start-up log for future		settings securely. Run the burner through several
reference.		cycles to verify prompt ignition and stable burner
Draft – Set the breech or furnace pressure to the		operation.
level specified by the appliance manufacturer. Typical
example: +0.10” W. C.
	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.

CG15, CG25, CG50 Burner Manual

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