151B0801 R5 3/28/2006
10
Fig. 5: 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. Refer to the
appliance rating plate of model for
temperature rise range.
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 appliance rating plate should be
consulted for model temperature rise
ranges. 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 used in
conjunction with multi-meters with
temperature measurement capabilities.
The return air should be measured at a
point where the thermometer will be well
within the air stream near the furnace
return air inlet. Actual location is not
particularly critical; however, avoid
locations where the temperature
readings could be affected by humidifier
bypass ducts, the inside radius of
elbows, etc.
The supply air temperature should be
measured at a point where the
thermometer will be well within the air
stream near the furnace supply air outlet.
Usually, the side mid-point of the supply
air plenum take-off is ideal, providing it is
out of the line of sight to the heat
exchanger. If the thermometer is within
the line of sight of the heat exchanger,
the supply air readings may be skewed
by radiant heat from the heat exchanger.
If the plenum take-off is unsuitable, the
supply air temperature may be measured
within the first 18 inches of the first
segment of supply air trunk duct.
If the temperature rise is outside the
recommended range, it may be adjusted
on direct drive equipped units by
selecting alternate circulation fan motor
speeds. If the temperature rise is too
high, speed the fan up. If the
temperature rise is too low, slow the fan
down.
C) Keep in mind that the stack
temperature varies directly with the
temperature rise. The higher the
temperature rise, the higher the stack
temperature will be, resulting in lower
efficiency. The lower the temperature
rise, the lower the stack temperature will
be, which, in some cases, may allow
condensation to form in the chimney and
other vent parts.
D) Test the high limit control to ensure
that it is operating correctly. This may be
done by temporarily removing the
circulator fan heating wire or neutral
wire. Turn of electrical power to the
furnace before working with the motor
wires. Be sure to protect any removed
wires from shorting out on metal furnace
parts. If the high limit test is successful,
shut off the electrical power to the
furnace, restore the proper motor wiring.
Finally, restore power to the furnace.
E) Operate the furnace through a
minimum of three full heating cycles.
During this time, check for fuel oil leaks,
gross air leakage from the supply air
ductwork, unusual noises originating
anywhere within the heating system
which may cause some concern or
annoyance to the home owner, etc.
F) Be sure that the homeowner is
familiar with the furnace. The
homeowner should be aware of the
location of electrical circuit breaker or
fuse, the location of any electrical
switches controlling the furnace, the
location of the oil tank shut-off valve and
how to operate the valve. The
homeowner should be informed where
the oil tank gauge is located and how to
read it.
It would be beneficial to review safety
issues with the home owner, such as the
danger of storing combustibles too close
to the furnace, hanging anything on the
furnace vent pipe, and especially the
dangers of indiscriminately pressing the
burner reset button.
IMPORTANT
: Be sure that the home
owner knows where the burner reset
switch is located, and is aware that the
reset switch is not to be activated more
than once without a thorough look for the
cause of the problem, (lack of fuel, etc.).
Be sure that the homeowner knows
when to quit trying to start the furnace
during these conditions and who to call
for emergency service.
