Bryant OBM098 Installation Instructions Manual page 12

3.3.3 Combustion Check
IMPORTANT
The heat exchanger metal surfaces may have oil and the
baffle insulation also contains binders. These products will
burn or evaporate when the unit operates for the first time.
Because of that, the smoke reading may be skewed during the
first minutes of operation. Therefore, the unit must operate
during at least 60 minutes before taking any readings to adjust
the combustion quality. Let the unit cool down before making
any adjustments.
IMPORTANT
The combustion check verification MUST be performed after
the nozzle replacement or the burner cleaning. After these
manipulations, the combustion parameters are necessarily
modified. Refer also to the burner instruction manual.
Pierce a test hole in the flue pipe, approximately 18 inches
1.
from the furnace breech. Insert the smoke test probe into
the hole. For installation using a sidewall venting, use the
orifice provided on the breech plate;
From a cold start, let the unit operate for about 5 minutes;
2.
Set the burner air setting until you have between 0 and 1
3.
on the Bacharach Scale (or a ''trace'');
Take a CO sample at the same test location where the
4.
2
#1 smoke reading was taken and make note of it.
Example: 13.8% of CO
Adjust the burner air setting to obtain a CO
5.
lower (or a O reading 2.0% higher) than the reading
2
associated with the ''trace'' of smoke. Example: 12.3% of
CO or 4.5% of O ;
2 2
This method of adjusting the burner will result in clean
6.
combustion (Bacharach smoke scale between 0 and a
''trace'') and ensure the proper functioning of the system.
The optimum CO level is around 12% to 13% (or 3.5% to
2
5.0% of O ).
2
3.3.4 Draft Regulator adjustment
On chimney installations only, a barometric draft regulator
(supplied with the furnace) must be installed, in order to ensure
proper draft through the furnace. The barometric damper must
be mounted with the hinge pins in a horizontal position and the
face of the damper vertical for proper functioning (see
instructions included with the damper.) After the furnace has
been firing for at least five minutes, the draft regulator should
be set to between -0.025" and -0.060" W.C.
Overfire pressure test
3.3.5
The overfire draft that is taken through the observation port,
located above the burner, is a measurement necessary to
determine if there is a blockage in the heat exchanger or the
flue pipe. Refer to the Technical Specifications in this manual
for overfire pressure values. A high pressure condition may be
caused by excessive combustion air, due to the air band being
too wide open, or a lack of flue draft (chimney effect) or some
other blockage, such as soot in the secondary section of the
heat exchanger or the use of an oversize nozzle input or high
pressure pump.
3.3.6 Vent Temperature Test
After having adjusted the burner combustion, insert a
1.
thermometer into the test hole in the breech pipe;
or 2.5% of O ;
2 2
reading 1.5%
2
The total vent temperature should be between 204
2.
and 302°C (400 and 575°F). If not, check for improper
air temperature rise, pump pressure, nozzle size or a
badly sooted heat exchanger.
CAUTION
Low flue gas temperatures increase the risk of
condensation. Adjust the total temperature at or higher
then 204°C (400°F) in order for the heat exchanger
warranty to remain in force.
3.3.7 Supply Air Temperature Rise Test
Operate the burner for at least 10 minutes;
1.
Measure the air temperature in the return air plenum;
2.
Measuring the air temperature in the largest trunk
3.
coming off the supply air plenum, just outside the
range of radiant heat from the heat exchanger. 0.3 m
(12") from the plenum of the main take-off is usually
sufficient;
The temperature rise is calculated by subtracting the
4.
return air temperature
temperature;
If the temperature rise is lower or exceeds the
5.
temperature specified in Table 6, change to the next
lower or higher blower speed tap, until the
temperature rise falls to the target. If the excessive
temperature rise cannot be increased or reduced by
changing fan speed,
obstructions, dirty or improper air filter, improper firing
caused by improper pump pressure or nozzle sizing.
3.3.8 Limit Control Check
After operating the furnace for at least 15 minutes, restrict
the return air supply by blocking the filters or the return air
register and allow the furnace to shut off on High Limit.
The burner will shut off but the blower will continue to run.
Remove the obstruction and the burner should restart
after a few minutes. The time required for the restart also
depends on the adjustment of the blower "OFF" delay.
3.3.9 Restart after Burner Failure
Set the thermostat lower than room temperature;
1.
Press the reset button on the burner primary control
2.
(relay);
Set the thermostat higher than room temperature;
3.
If the burner motor does not start or ignition fails, turn
4.
off the disconnect switch and CALL A QUALIFIED
SERVICE TECHNICIAN.
CAUTION
Do not attempt to start the burner when excess oil has
accumulated, when the furnace is full of vapour or when
the combustion chamber is hot.
12
from the supply air
investigate for ductwork