18, Circulating Air Blower - Nordyne O4MD Installation, Operation And Maintenance Manual

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.
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.
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 fire 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.
Check the oil pump pressure, normally, 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 002 reading will range between 11.5% to
13.5%.
After the air adjustments have been completed, and the
air shutter or air adjustment plate has been secured, take
another smoke test to ensure that the values have not
changed.
The maximum combustion efficiency based on flue gas
high CO2 content generally lies between a No. 1 and No.
2 smoke spot on the Bacharach Scale. This is not the
optimum setting; however, because dust will inevitably
build up on the air moving components of the oil burner
assembly. This will result in decreased air supply with the
potential result of soot building up in the flue gas
passageways of the heat exchanger. Soot behaves as an
insulator and impairs good heat transfer. Stack
temperature will increase, and the overall efficiency will
decrease. As a means of avoiding this problem, the
smoke should be held at a trace.
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 range between 350°F
to 450°F, but could be as high as 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. Typical temperature rise values range
between 65°F and 90°F.
If the venting from the furnace to the chimney is long, or
exposed to cold ambient temperatures, consider using L-
Vent to reduce stack loss.
18. CIRCULATING AIR BLOWER
The furnace is equipped with direct drive blower system.
Direct drive blower speed adjustments are not normally
required in properly sized extended plenum duct
systems. The motor RPM and air CFM delivery will vary
automatically to accommodate conditions within the usual
range of external static pressures typical of residential
duct systems. Under-sized duct systems may require a
higher blower speed to obtain a reasonable system
temperature rise. Some older duct systems were not
designed to provide static pressure. They typically feature
special reducing fittings at each branch run and lack
block ends on the trunk ducts. These systems may
require modification to provide some resistance to the
airflow to prevent over- amping of the direct drive blower
motor. Selecting a lower blower speed may correct this
problem.
Direct drive blower speeds are adjusted by changing the
"hot" wires to the motor winding connections. Please
refer to wiring diagrams in Appendix B or the wiring
diagram label affixed to the furnace.
THE NEUTRAL WIRE (normally the white wire) IS /
NEVER MOVED TO ADJUST THE BLOWER SPEED.
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] ] 153B0801