BURNER ELECTRODES
Correct positioning of the electrode tips with respect to each other, to the fuel oil nozzle, and to the rest of the burners is essential for smooth light ups and proper operation. The electrode tips should be adjusted to a gap of 5/32”, 1/16” ahead of the nozzle, 5/16” above the centerline of the nozzle. The “Z” dimension (front edge of the burner head to the front face of the nozzle is 1-1/8 inches.
Electrode positioning should be checked before the first firing of the furnace.
The electrode porcelains should be free of cracks, the electrode tips should be tapered and free of burrs, and the contact rods must be clean and be in firm contact with the ignition transformer contact springs. The electrodes must not come into contact with the burner head.
OIL BURNER SET-UP
The burner air supply is adjusted to maintain the fuel to air ratio to obtain ideal combustion conditions. A lack of air causes "soft" and "sooty" flames, resulting in soot build-up throughout the heat exchanger passages. Excess combustion air causes a bright roaring fire and high stack temperatures resulting in poor fuel efficiency.
PREPARATIONS:
Drill a ¼” test port in the venting, ideally at least 2 flue pipe diameters away from the furnace breeching, if venting horizontally from the furnace, or from the flue pipe elbow if venting vertically before reaching the furnace. (See Figures 4 and 5).
The test port will allow flue gas samples to be taken and stack temperatures to be measured.
Before starting the burner, check the burner alignment with the combustion chamber (fire pot), check that the correct nozzle is tightened into place, and that the burner electrodes are properly positioned.
The Beckett burner bulk air band is should be closed, and the air shutter initial setting should be approximately 7.00.
Note A: Locate hole at least 6 inches on the furnace side of the draft control.
Note B: Ideally, hole should be at least 12 inches from breeching or elbow.
PROCEDURE:
Start the burner and allow it to run at least ten minutes. Set the air shutter to give a good flame visually. The combustion air supply to the burner is controlled by manipulating the air shutter on the left side of the burner, and, if necessary, the bulk air band. To adjust, loosen the bolt on the movable shutter. Move the shutter gradually until a good flame (visually) has been achieved. Re- snug the bolt.
Check the initial draft setting as the furnace warms up. The draft may be measured at the test port. The breech draft should be approximately - 0.05” w.c. to obtain an over fire draft reading of - 0.02 inches w.c.
Check the oil pump pressure. Standard operating pressure is 100 PSIG.
After reaching steady state, take a smoke test. If not indicating a trace, set the combustion air controls to provide a trace.
Typically, the CO2 reading will range from 11.5% to 13.5%.
After the air adjustments have been completed, and the air shutter or air adjustment plate has been secured, re- check the over fire draft and take another smoke test to ensure that the values have not changed.
Figure 6: Checking Over-Fire Draft.
SMOKE TEST NOTE:
If oily or yellow smoke spots are found on the smoke test filter paper, it is usually a sign of unburned fuel. This indicates poor combustion. This type of problem may be caused by excess draft,
excess air, or contaminated fuel. Do not ignore this indicator.
STACK TEMPERATURE:
Stack temperature will vary depending on fuel input, circulating air blower speed, and burner set up, etc. In general, stack temperature should typically range between 380°F to 550°F, assuming that the combustion air is approximately room temperature (65°F - 70°F). In general, lower stack temperature indicates greater efficiency; however, excessively low stack temperature can lead to condensation forming in the chimney and / or venting. Sulphur and similar contaminants in the fuel oil will mix with condensation to form acids. Acids and resultant chemical salts will cause rapid deterioration of the chimney and venting components, and may attack the furnace.
If the flue gases are below the range, it may be necessary to slow down the blower fan. If the flue gases are above the range, the blower fan may require speeding up. Stack temperature varies directly with the system temperature rise. System temperature rise is the difference between the furnace outlet temperature and furnace inlet temperature as measured in the vicinity of the connection between the plenum take-offs and the trunk ducts.
If the venting from the furnace to the chimney is long, or exposed to cold ambient temperatures, it may be necessary to use L-Vent as the vent connector to reduce stack temperature loss to prevent condensation. The venting should be inspected annually to ensure that it is intact.
FURNACE INSTALLATION SET- UP
The furnace must be set up as the final step in the installation.
A)The oil burner must be set up following the procedures outlined above.
B)The WML-C models should operate within a temperature rise of 45°F to 75°F. The MPL-B temperature rise range should be 50°F to 80°F. To determine the temperature rise, measure the supply air and return air temperatures when the furnace has reached steady state conditions. This is the point at which the supply air temperature stops increasing relative to the return air temperature. The furnace may have to run 10 to 15 minutes to reach steady state conditions. The measurements may be made with duct thermometers or thermocouples
