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3.3.3 Combustion Check
CAUTION
The heat exchanger metal surfaces may have oil and the insulation in
the sound trap assembly 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.
1. Pierce a test hole in the flue pipe, approximately 18 inches 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.
2. From a cold start, let the unit operate for about 5 minutes.
3. Set the burner air setting until you have between 0 and 1 on the
Bacharach Scale (or a ‘’trace’’);
4. Take a CO2sample at the same test location where the ‘’trace’’ of
smoke reading was taken and make note of it. Example: 13.8%
of CO2or 2.5% of O2;
5. Adjust the burner air setting to obtain a CO2 reading 1.5% lower
(or a O2reading 2.0% higher) than the reading associated with
the ‘’trace’’ of smoke. Example: 12.3% of CO2or 4.5% of O2;
6. This method of adjusting the burner will result in clean
combustion (Bacharach smoke scale between 0 and a trace) and
ensure the proper functioning of the system. The optimum CO2
level is around 12% to 13% (or 3.5% to 5.0% of O2).
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.
3.3.5 Overfire pressure test
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
1. After having adjusted the burner combustion, insert a
thermometer into the test hole in the breech pipe;
2. The total vent temperature should be between 204 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.
Also refer to section 2.5 for proper flue pipe sizing.
CAUTION
Low flue gas temperature increases the risk of condensation. Adjust
the total flue gas 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
1. Operate the burner for at least 10 minutes;
2. Measure the air temperature in the return air plenum;
3. Measuring the air temperature in the largest trunk 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;
4. The temperature rise is calculated by subtracting the return
air temperature from the supply air temperature;
5. If the temperature rise is lower or exceeds the temperature
specified in Table 7, 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, investigate for
ductwork 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
1. Set the thermostat lower than room temperature.
2. Press the reset button on the burner primary control (relay)
3. Set the thermostat higher than room temperature.
4. If the burner motor does not start or ignition fails, turn 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.
3.4 EMERGENCY HEATING MODE -
VARIABLE SPEED MOTOR (ECM)
If the ECM blower motor is defect and that no spare is available
right away, you can temporarily replace it with a conventional
fractional PSC blower motor. Connect neutral wire to neutral
terminal on the control panel of the machine and the hot line to
the EAC terminal. This one is working as long as heating or
cooling is requested, and the blower will work until a new ECM
motor is installed.
CAUTION
We recommend using this mode only for a short period of
time since it affects the efficiency of the unit and the user
comfort.
