most cases, adjustment of the end air shutter will be all that is
necessary.
When the trace smoke has been established, measure the
CO
2
or O
2
in the flue gas. Typically, the CO
2
reading will be ap-
proximately 13% or the O
2
reading approximately 3.3%.
Open the end air shutter (or open the bulk air band if neces-
sary) until the CO
2
reading drops 1 or 2 percentage points, or, if
measuring O
2
content, until the O
2
reading increases 2 or 3
percentage points.
Take another smoke test; it should now be zero smoke. If the
smoke test reads zero, tighten up the end air shutter, and the
bulk air band.
Re--test the draft and the CO
2
or O
2
to be certain that the set-
tings have not shifted.
NOTE: If oily or yellow smoke sports 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 tem-
perature should range between 350
°
F to 450
°
F, but could be
as high as 550
°
F, assuming that the combustion air approxi-
mately room temperature (65
°
F -- 70
°
F). In general, lower
stack temperature indicates greater efficiency; however, ex-
cessive low stack temperature can lead to condensation form-
ing in the chimney and/or venting. Sulfur and similar
contaminants in the fuel oil will mix with condensation to form
acids. Acids and resultant chemical salts will cause rapid dete-
rioration of the chimney and venting components, and may at-
tack 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 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 the 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 ex-
posed to cold ambient temperatures, it is advisable to insulate
the venting with a removable, non--combustible, wrap--around
type insulation to reduce stack temperature loss. The vent
should be inspected annually to ensure that it is intact.
FINAL CHECK OUT
Before the final test cycle, carefully examine the complete
heating system for leaks. The hot vent can be checked with a lit
taper for signs of air movement around joints or seams.
Ensure that all safety devices and electrical components have
been set for normal operation. Ensure that all electrical con-
nections are tight and that the wiring is secure.
IMPORTANT:
Please review the following items with the homeowner:
•
where the circuit breaker or fuse is located in the main
electrical panel.
•
where the furnace switch is located, and the switch “on”
and “off” positions if not obvious.
•
where the oil shut--off valve from the oil storage tank is
located.
•
how to operate the thermostat, and other related acces-
sories.
•
how to operate the manual reset button on the primary
control, and especially when not to push the reset button.
•
how and where to visually inspect the venting system for
leaks or other problems.
•
how to inspect, clean and replace the air filter, and other
homeowner maintenance procedures.
•
who to call for emergency service and routine annual
service.
•
the terms and conditions of the manufacturer's warranty
and the contractor's warranty.
Unitary Products Group
11
035-14289-000 Rev. A (0701)
