14
8. After all the set up procedures mentioned above have
been completed, the burner should be fired and an
inspection mirror should be used to observe the flame
pattern at the tip of the nozzle. Any irregularities such as
burning to one side or pulsating flame patterns should
be corrected by changing the nozzle.
2.3)
SEQUENCE OF OPERATION
Using schematic diagram in Figure 11, p. 23, follow the
sequences of operation through the different modes.
NOTE:
ECM variable speed motors deliver infinitely variable
CFMs. At start-up the motor increases its speed
gradually, in order to lower noise perception. ECM
motors ramp down in the same gradual fashion as
they do on start-up. ECMs are energized by 120V,
whenever power is available to the furnace control.
However, they operate only when 24V motor control
signals are received.
2.3.1) Oil fired heating mode
1. The thermostat closes R to W.
2. Burner motor fan pre-purges the combustion chamber
for 10 to 15 seconds, establishing the combustion air
pattern. During this time a spark is also established. The
fan starts at 13% of nominal heating for a period
equivalent to the “Pre-Run Delay”. Refer to Tables 6 &
7, p. 19 & 20.
3. The solenoid valve opens and a flame is established. A
short time after that, the ignition transformer ceases
sparking.
4. After the “Pre-Run Delay” the blower slightly increases
its speed for a period of time equivalent to the “Short-
Run Delay”. Refer to Tables 6 & 7, p. 19 & 20.
5. After the “Short-Run Delay” the blower increases its
speed in order to reach the CFMs indicated in Tables 6
& 7, p. 19 & 20.
6. The call for heat is satisfied.
7. The solenoid valve closes, the burner motor stops and
the flame extinguishes.
8. The blower slows down gradually to 38% of nominal
CFMs for a period of 3 minutes and then stops.
2.3.2) Cooling
mode
NOTE:
On units using a 2-stage compressor, the terminal
Y1 must be used. Once the Y1 terminal on the
electronic control receives a 24 V signal, the airflow
is reduced by 55% percent. If a single stage
compressor is used, do not use the Y1 terminal.
1. The R - G-and R - Y/Y2 thermostat contacts close. The
R-Y/Y2 circuit starts the outdoor unit, and the R - G
circuit starts the blower at cooling speed. Refer to
Tables 6 & 7, p. 19 & 20.
2. When the call for cooling is satisfied, the R - G and R -
Y/Y2 thermostat contacts open. The cooling unit stops
and furnace blower gradually slows down to 50% of
nominal CFMs for a period of 3 minutes.
2.3.3) Continuous Blower Mode
1. When the R – G thermostat contacts close, the blower
functions at 64%, 75% or 86% of cooling airflow,
depending on the adjustment of the DIP switches. Refer
to Tables 6 & 7, p. 19 & 20.
2. When the R – G thermostat contacts open, the blower
stops immediately.
2.3.4) Heat Pump – Heating / Cooling Mode
NOTE 1:
A dual-fuel thermostat is required when a variable
speed furnace is used with a heat pump. See dual-
fuel thermostat Installation Instructions for
interface connections. The interface prevents
simultaneous operation of both the furnace and
heat pump and prevents direct transition from heat
pump to furnace operation.
NOTE 2:
On units using 2-stage compressors, terminal Y1
must be used. When Y1 on the electronic control
board receives a 24 V signal, the airflow is cut by
55%. If a single stage compressor is used, do
NOT use terminal Y1.
a. Cooling
Mode
1. The thermostat contacts R - G, R - Y/Y2 and R - O
close. The R - Y/Y2 circuit starts-up the outdoor cooling
unit, the R - O maintains the reversing valve in the
cooling mode and the R - G circuit starts-up the blower
at cooling speed. Refer to Tables 6 & 7, p. 19 & 20.
2. When the call for cooling is satisfied, the R - G, R - Y/Y2
and R - O contacts open. The cooling unit stops and the
furnace blower slows down gradually to 50% of nominal
CFMs for a period of 3 minutes.
b.
Heating Mode Thermo Pump
1. The thermostat contacts R - G and R - Y/Y2 close. The
R - G circuit starts-up the blower at heating speed by
way of the Thermo Pump. Refer to Tables 6 & 7, p. 19 &
20.
2. When the call for heat is satisfied, the thermostat
contacts open and the furnace blower gradually reduces
its speed to 50% of nominal CFMs for a period of 3
minutes.
2.3.5) Defrost
Mode
When the R - W and R - Y/Y2 circuits are closed by the
thermostat and the heat pump, the electronic control starts-
up the burner and the blower in the oil heating mode during
defrost.
2.4)
FAN ADJUSTMENT CHECK
This furnace is equipped with an ECM variable speed motor.
The blower is adjusted at the factory to deliver the required
oil heating airflow at 0.75 USGPH and 3.0 tons of cooling on
models with a maximum input of 105,000 BTU/H. The same
applies to units with 0.85 USGPH input, 5 tons of cooling and
a maximum input of 154,000 BTUH.
Refer to Tables 3A to 4D, p. 15 for
information on how to
adjust the DIP switches for other blower speeds for heating
and cooling.
2.5)
LIMIT CONTROL CHECK
After the furnace has been in operation for at least 15
minutes, restrict the return air supply by blocking the filters or
closing the return registers and allow the furnace to shut
down on High Limit. The burner will shut off but the main
blower should continue to run.
Remove the restriction and the burner should come back on
in a few minutes.
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