11
then the thermostat circuit is opened and the burner will go into a
15 seconds post-purge and then shut down;
3.
Once the burner blower shuts down, after the post-purge, the
pressure switch contacts will re-close. If the call for heat remains,
the burner will re-start. If the blockage still exists, the thermostat is
again opened, and the burner post- purges again. The post-purge
function thus becomes an inherent anti-short cycling device;
4.
The unit will essentially go into a continuous re-cycling/post-purge
mode with no heat being supplied to the dwelling, which will prompt
a service call;
5.
If, during the re-cycling/post-purges, the blockage of the terminal is
removed, the burner will immediately fire up at the end of the
current post-purge cycle.
During operation
If the terminal vent or intake openings become blocked to the point
where the set point of the pressure switch is exceeded, during a firing
cycle, the burner flame will shut down and the burner will go into the
indefinite recycling/post-purge mode as described above, until the
blockage is removed.
3.3- CHECKS AND ADJUSTMENTS
3.3.1- General
During initial start-up and subsequent yearly maintenance calls, the
furnace must be thoroughly tested.
Open the oil bleed port screw and start the burner. Allow the oil to drain
into a container for at least 10 seconds. Slowly close and tighten the
bleed screw. The oil should flow absolutely free of white streaks or air
bubbles to indicate that no air is being drawn into the suction side of the
oil piping and pump. Fire the burner. Adjust the oil pressure as indicated
in Table 4.
IMPORTANT
The burner must be put in operation for at least 10
minutes before any test readings are taken. For new
installations, set up the burner to the settings in Table 4
before firing. These are rough adjustments but they will
ensure that the burner will start and run smoke-free in
advance of the fine adjustments being made.
3.3.2- Restart after burner failure
1.
Set thermostat lower than the room temperature;
2.
Press the reset button on the burner primary control (relay);
3.
Set thermostat higher than the room temperature for 10 seconds,
then set lower than room temperature. This will start the pre-purge
cycle. Repeat twice;
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 very hot. Always keep the
supply valve closed if the burner is shut down for an
extended period of time.
4.
Set thermostat higher than the room temperature;
5.
If the burner motor does not start or ignition fails, turn off the
disconnect switch
and
CALL
A
QUALIFIED
SERVICE
TECHNICIAN.
3.3.3- Combustion chamber curing
Some moisture and binders remain in the ceramic combustion chamber
after fabrication. It is important to clear the chamber of this residue
before testing. If you smoke test before curing, the instrument may
become damaged. To cure the chamber, run the unit for 3 consecutive
cycles, with 3 minutes of elapsed time in between each cycle. Each burn
cycle should be 3 minutes long. The exhaust will have a pungent odour
and produce a white cloud of steam.
3.3.4- Smoke / CO2 test
1.
On chimney installations, pierce a test hole in the smoke pipe 18
inches above the furnace breach. On side-wall vented installations,
remove the threaded cap from the extended test pipe that is welded
into the 4-bolt breach plate. Insert the smoke test instrument probe
into the open hole;
2.
From a cold start, let the unit operate during 5 to 10 minutes;
3.
Set the burner air setting until just a trace of smoke results (#1 on
the Bacharach scale);
4.
Take a CO
2
sample at the same test location where the #1 smoke
reading was taken and make note of it. Example: 13.8% of CO
2
or
2.5% of O
2
;
5.
Adjust the burner air setting to obtain a CO
2
reading 1.5% lower (or
an O
2
reading 2.0% higher) than the reading associated with the #1
smoke. Example: 12.3% of CO
2
or 4.5% of O
2
;
6.
This method of adjusting the burner will result in clean combustion
and ensure the proper functioning of the system.
3.3.5- Perform the supply air temperature rise test
1.
Operate the burner for at least 10 minutes;
2.
Measure the temperature of the air in the return air plenum;
3.
Measure the temperature of the air in the largest trunk coming off
the supply air plenum, just outside the range of radiant heat coming
off the heat exchanger; 0.3 m (12") away from the plenum on 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 exceeds the temperature specified in Table
4, change to the next higher blower speed tap until the temperature
rise falls to this temperature or below. If the excessive temperature
rise cannot be reduced by increasing fan speed, investigate for
ductwork restriction(s), dirty or improper air filter, over firing caused
by excessive pump pressure, or improper nozzle sizing.
3.3.6- Vent temperature test
1.
After 5 to 10 minutes of operation, place a thermometer in the test
hole located in the breach pipe;
2.
The 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 for a badly sooted heat exchanger;
3.
Check the minimum permitted temperature at the base of the
chimney. Refer to the installation code in order to avoid the risk of
condensation in the chimney.
3.3.7- Overfired pressure test procedure
1.
To read the pressure, replace the glass with the washer supplied
with the appliance;
2.
After the test, put the glass back in place in the sight glass
assembly;
3.
Verify that the pressure reading corresponds to the one specified
in Table 4. Also see Figure 3.
