Trane YCZ036F1/3M0B, YCZ035F1 Sequence of Operation, Starting the Unit in the GAS Heating Mode

START - UP

8.Set the thermostat at the desired temperature setting and the unit will function automatically.

STARTING THE UNIT IN THE GAS HEATING MODE

1.Check to make sure all grilles and registers are open and all unit access doors are closed before start-up.

2.Purge the gas supply line of air by opening the union ahead of the unit. When the odor of gas is detected, retighten the union and wait five (5) minutes before proceeding.

3.Set the wall thermostat to its lowest position and place the fan switch in the AUTO or ON position.

4.Open the main gas valve(s) and turn on the unit power supply.

5.Reset the heating temperature lever on the room thermostat at the highest value above room temperature. The combustion blower motor should energize. The main burners should light within 20-25 seconds. Initial start may be delayed somewhat if the unit has not been purged and air is trapped in the gas line.

NOTE: Blue smoke produced by the heat exchanger during the initial burner firing is caused by a thin film of oil on the surface of the heat exchanger. This oil will burn off quickly.

6.Cycle the thermostat OFF and ON a few times at a rate of not more than once every thirty (30) seconds. Check both the control operation and the burner operating conditions.

MANIFOLD PRESSURE

1.Connect a manometer to the pressure tap at the outlet side of the unit’s gas valve. Read the manifold pressure with the main burners firing.

2.If the manifold pressure reading does not match the value indicated on the unit nameplate, the unit pressure regulator must be adjusted as follows:

a.Remove the cover screw on the gas regulator located on the front side of the unit’s gas valve.

b.Turn the adjusting screw clockwise to increase manifold pressure or counterclockwise to decrease manifold pres- sure.

3.Check the temperature rise during furnace operation to insure that it falls within the range specified on the unit nameplate.

4.If the temperature rise noted is outside of the specified limits, adjust the indoor air flow to cause the temperature rise of the heat exchanger to fall within the required range.

SEQUENCE OF OPERATION

Operation of the unit heating or cooling cycles is controlled by the setting of the system switch on the room thermostat. Once the system switch is placed either in the “HEAT” or “COOL” position, unit operation is automatic. A fan switch on the thermostat also provides for it continuous operation of the evaporator fan when desired. The fan switch “ON” position provides continuous opera- tion while the “AUTO” position provides operation during the heat- ing or cooling cycles.

HEATING CYCLE

Thermostat call for heat ( 2-stage thermostat)

Call for 1st stage only:

(R)and (W1) thermostat contacts close signaling the control mod- ule (IGN) to run its self-check routine. After the control has verified that the pressure switch (PS) contacts are open, the limit switch (TCO) contacts are closed, and the flame rollout (FL) switch is closed, the induced draft blower (CBM) will be energized on high speed for approximately 15 seconds.

After the induced draft blower (CBM) has come up to speed, the control will verify that the pressure switch (PS) contacts are closed and switch the induced draft blower to low speed for an additional 5 seconds of prepurge. The gas valve (GV) is energized in the first stage to permit gas flow and the spark ignitor (IP) is energized. The flame detector (FD) confirms that ignition has been achieved within the 7 second trial period.

As the flame detector confirms that ignition has been achieved the delay to indoor fan on period begins timing and after approximately 45 seconds, the indoor blower motor (IDM) will be energized at low speed and will continue to run during the heating cycle.

Call for 2nd stage after 1st stage:

(R)and (W2) thermostat contacts close signaling a call for second stage heat. The induced draft motor (CBM) is energized on high speed and the gas valve on second stage. After approximately 30 seconds the control energizes the indoor blower on high speed.

2nd stage satisfied, 1st stage still called:

(R)and (W2) opens, the induced draft blower is reduced to low speed the gas valve is reduced to first stage. After aprox. 30 seconds the indoor blower motor is reduced to low speed.

1st stage satisfied:

(R)and (W1) opens, the gas valve (GV) will close. The induced draft blower (CBM) will be de-energized after approximately 5 seconds postpurge. The indoor blower motor (IDM) will continue to run for the fan off period (field selectable 60 or 90 seconds [by jumpers]), then will be de-energized by the control module.

Thermostat satisfied:

(R)and (W1/W2) (jumpered) contacts open signaling the control module to close the gas valve and de-energize the induced draft blower after approximately 5 second postpurge. The I.D. blower motor will continue to operate at the current speed for 60 or 90 seconds after the flames are extinguished .

SAFETY SEQUENCES

This product is equipped with safety devices to protect against abnormal conditions.

The temperature limit switch (TCO) is located in the gas com- partment on the vestibule panel above the burner assembly. This automatic reset device protects against excessive leaving air temperature. If this device opens, the gas valve is immediately closed and will not permit operation until the limit switch closes.

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