Installation manual

035-19599-001 Rev. A (1103)
20 Unitary Products Group
Drain Connection - The following steps apply to all models. For hori-
zontal application, also follow the procedure for relocating the trap
assembly and installing drain hoses.
1. It is recommended that either ½” (12.7 mm) or ¾” (19.05 mm) PVC
or equivalent pipe be field installed as drain pipe. The condensate
piping may be tied together with the air conditioning condensate
drain if the air conditioning condensate drain line is trapped
upstream of the tie-in, the combined drains are constructed of the
same material and if Local Codes allow the condensate drain to be
connected to the air conditioning coil drain.
2. All pipe joints must be cleaned, de-burred and cemented using
PVC primer and cement.
3. If the furnace contains an internal condensate trap, an external
condensate trap is not recommended.
4. If a condensate pump is used it must be suitable for acidic water.
5. A field-supplied neutralizer can be installed in the condensate
drain line, where required, external to the furnace.
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 SWITCHES
This furnace is supplied with a pressure switch, which monitors the flow
through the combustion air/vent piping system. This switch de-ener-
gizes the ignition control module and the gas valve if any of the follow-
ing conditions are present. Refer to Figure 31 for tubing connections.
1. Blockage of combustion air piping or terminal.
2. Blockage of vent piping or terminal.
3. Failure of combustion air blower motor.
4. Blockage of condensate drain piping.
LIMIT CONTROLS
There is high temperature limit control located on the furnace vestibule
panel near the gas valve. This is an automatic reset control that pro-
vides over temperature protection due to reduced airflow, that may be
caused by a dirty filter, or if the indoor fan motor should fail. The control
module will lockout if the limit trips 5 consecutive times.
SECTION X: START-UP AND
ADJUSTMENTS
The initial start-up of the furnace requires the following additional
procedures:
IMPORTANT: All electrical connections made in the field and in the fac-
tory should be checked for proper tightness.
When the gas supply is initially connected to the furnace, the gas piping
may be full of air. In order to purge this air, it is recommended that the
ground union be loosened until the odor of gas is detected. When gas is
detected, immediately retighten the union and check for leaks. Allow
five minutes for any gas to dissipate before continuing with the start-up
procedure.
Plug all unused condensate trap, condensate pan and inducer drain
connection points using plugs provided.
FIGURE 28: Horizontal Condensate Drain Connections
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.
3
1
2
A
B
C
RIGHT
AIRFLOW
(INDUCER
HIGH)
D
5
4
LEFT
AIRFLOW
(INDUCER
HIGH)
FIGURE 29: Pressure Switch Tubing Routing
Perform the following procedures only after the condensate trap
has been properly piped to a drain connection using the procedure
in this instruction. Be sure proper ventilation is available to dilute
and carry away any vented gas.
DOWNFLOW / HORIZONTAL