292278-UIM-A-0108
Unitary Products Group
21
CONDENSATE DRAIN
The condensate trap must be filled with water before putting the furnace
into operation. Perform the following procedures only after the conden-
sate trap has been properly piped to a drain connection using the pro-
cedure in this instruction.
The recommended procedure is as follows:
1.
Disconnect the condensate drain hose from the induced draft
blower discharge.
2.
Elevate this hose and fill with water using a funnel.
3.
Replace the condensate drain hose and clamps.
IMPORTANT:
If this procedure is not followed, the unit may not properly
drain on initial start up.
CONDENSATE DRAIN TERMINATION
DO NOT terminate condensate drain in a chimney, or where the drain
line may freeze. The line must terminate at an inside drain to prevent
freezing of the condensate and possible property damage.
DO NOT trap the drain line at any other location than at the condensate
drain trap supplied with the furnace.
A condensate sump pump MUST be used if required by local codes, or
if no indoor floor drain is available. The condensate sump pump must
be approved for use with acidic condensate.
CONDENSATE DRAIN TRAP AND DRAIN FREEZE
PROTECTION
Special precautions MUST be made if installing furnace in an area
which may drop below freezing. This can cause improper operation or
damage to the equipment. If the furnace is installed in an area that has
the potential of freezing, the drain line and the drain trap must be pro-
tected. Use a 3 to 6 watt per foot at 115 vac, 40º F (4.4° C) self-regulat-
ing, shielded and waterproof heat tape. Wrap the drain trap and the
drain line with the heat tape and secure with ties. Follow the heat tape
manufacturer's recommendations.
SECTION IX: SAFETY CONTROLS
CONTROL CIRCUIT FUSE
A 3-amp fuse is provided on the control circuit board to protect the 24-
volt transformer from overload caused by control circuit wiring errors.
This is an ATO 3, automotive type fuse and is located on the control
board.
BLOWER DOOR SAFETY SWITCH
This unit is equipped with an electrical interlock switch mounted in the
blower compartment. This switch interrupts all power at the unit when
the panel covering the blower compartment is removed.
Electrical supply to this unit is dependent upon the panel that covers the
blower compartment being in place and properly positioned.
ROLLOUT SWITCH CONTROLS
These controls are mounted on the burner box assembly. If the temper-
ature in the burner box exceeds its set point, the ignition control and the
gas valve are de-energized. The operation of this control indicates a
malfunction in the combustion air blower, heat exchanger or a blocked
vent pipe connection. Corrective action is required. These are manual
reset controls that must be reset before operation can continue.
PRESSURE CONTROLS
Pressure Sensor -
This furnace is equipped with a pressure sensor
mounted on the furnace control board. This sensor monitors combus-
tion airflow through furnace and piping systems. If any of the conditions
listed above are detected by the pressure sensor, the control board will
prevent a hazardous condition from occurring by speeding up the com-
bustion blower motor in order to maintain adequate combustion airflow.
If the combustion blower is already turning at full speed, the furnace
control will then start reducing the input to the furnace in order to main-
tain proper combustion with the amount of combustion airflow available.
If there is not enough combustion air available to give proper combus-
tion even at the minimum input rate (35%), the control will close the gas
valve and shut off the burners.
Pressure Switch -
This furnace is equipped with a pressure switch
mounted on the furnace vestibule panel. This switch monitors the flow
through the combustion air/vent system. The switch will close at the
beginning of each cycle when adequate combustion airflow is estab-
lished. However, this switch may be open under certain conditions
when the burners are lit. The pressure sensor is the primary flow sen-
sor.
1.
Blockage of combustion air piping
2.
Blockage of vent piping or vent terminal
3.
Failure of combustion air blower motor or blower wheel.
4.
Blockage of condensate drain piping.
LIMIT CONTROLS
Limit Switch -
This furnace is equipped with a high temperature limit
control mounted to the left side of the furnace vestibule panel. This limit
switch will open and shut off gas to the burners if it detects excessive air
temperature in the furnace, which can be caused by any of the following
conditions:
1.
Dirty filter
2.
Failure of the circulating blower motor or wheel
3.
Too many supply or return registers closed or blocked.
Temperature Sensor -
This furnace is also equipped with a tempera-
ture sensor mounted to the right side of the vestibule panel, near the
top of the furnace. This sensor monitors the temperature of the air being
supplied to the home. If the sensor detects air temperature higher than
its setting, the furnace control will first speed up the circulating blower
motor in order to try to increase the amount of airflow being delivered,
thereby reducing the air temperature. If the blower motor is already
turning at full speed, the control will then start reducing the input to the
furnace to try to reduce the air temperature. If the supply air tempera-
ture is too high even at the minimum input rate (35%), the control will
close the gas valve and shut off the furnace.
SECTION X: START-UP AND
ADJUSTMENTS
NOTE:
In order that this furnace will operate properly, it is required that
all of the startup procedures in this section be followed:
Main power to the unit must still be interrupted at the main power
disconnect switch before any service or repair work is to be done to
the unit. Do not rely upon the interlock switch as a main power dis-
connect.
Blower and burner must never be operated without the blower
panel in place.
Perform the following procedures only after the condensate trap
has been properly piped to a drain connection using the procedure
in this instruction.
