Control Wiring (Class Ii); Step 5-Unit Startup; Pre-Start Quick Checklist; Starting The Unit In The Cooling Mode - Trane 18-EB24D1-19 Installer's Manual

Control Wiring (Class II)

Low voltage control wiring should not be run in conduit with power
wiring unless Class 1 wire of proper voltage rating is used. Route
the thermostat cable or equivalent single leads of No. 18 AWG
colored wire from the thermostat subbase terminals through the
rubber grommet on the unit. See Figures 1-12 (pages 4-15) for the
control entry (24V Entry) location. Make connections as shown on
the field wiring diagram Figure 26, page 24.
Do not short thermostat wires since this will damage the control
transformer.
Refer to Table 2 for recommended wire sizes and lengths for install-
ing the unit thermostat. The total resistance of these low voltage
wires must not exceed one (1) ohm. Any resistance in excess of 1
ohm may cause the control to malfunction because of the exces-
sive voltage drop.
Table 2. Thermostat Wire Size and Maximum Length
WIRE SIZE
18
16
14
IMPORTANT: Upon completion of wiring, check all electrical con-
nections, including factory wiring within the unit, and make sure all
connections are tight. Replace and secure all electrical box covers
and access panels before leaving the unit or turning on the power
to the unit.
Step 5—Unit Startup

Pre-Start Quick Checklist


Is the unit properly located and level with the proper
clearance? See Figures 1-12, pages 4-15. See Step 2-Review
Location and Clearances on page 4.

Is the duct work correctly sized, run, taped, insulated, and
weatherproofed with proper unit arrangement?
Ductwork Installation section on page 22.

Is the condensate line properly sized, run, trapped, and
pitched? See Condensate Drain Piping section on page
22.

Is the filter of the correct size and quantity? Is it clean and in
place? See Air Filter Installation section on page 22.

Is the wiring properly sized and run according to the unit
wiring diagram? See Electrical Wiring section on page 23.

Are all the wiring connections, including those in the unit,
tight? See Electrical Wiring section on page 23.

Has the unit been properly grounded and fused with the
recommended fuse size? See Electrical Wiring section on
page 23.

Is the thermostat well located, level, and correctly wired?
See Electrical Wiring section on page 23.

Have the air conditioning systems been checked at the service
ports for charge and leak tested if necessary?
MAXIMUM LENGTH (Ft)
75
125
200
See
Installer's Guide

Do the condenser fan and indoor blower turn free without
rubbing, and are they tight on the shafts?

Has all work been done in accordance with applicable local
and national codes?

Are all covers and access panels in place to prevent air loss and
safety hazards?
Starting the Unit in Cooling Mode
▲ !
Safety Hazard. Do not operate the unit without the evapora-
tor fan access panel or evaporator coil access panel in place.
Reinstall the access panels after performing maintenance
procedures on the fan. Operating the unit without the access
panels properly installed may result in severe personal injury
or death.
▲ !
Before starting the system on the cooling cycle, turn the ther-
mostat switch to OFF and close the unit disconnect switch. This
is a precaution against foaming at startup which could damage
the compressor bearings.
NOTE: See the section on Sequence of Operation , page 26
for a description of the cooling operating sequence.
To start the unit in the cooling mode, set the comfort control to
COOL and to a setting below room temperature. The condenser
fan motor, compressor and evaporator fan motor will operate au-
tomatically. Continuous fan mode during Cooling operation may
not be appropriate in humid climates. If the indoor air exceeds
60% relative humidity or simply feels uncomfortably humid, it is
recommended that the fan only be used in the AUTO mode.
Operating Pressure Checks
After the unit has operated in the cooling mode for a short period of
time, install pressure gauges on the gauge ports of the discharge
and suction line valves (behind the Compressor access panel).
Check the suction and discharge pressures and compare them to the
normal operating pressures provided in the unit's SERVICE FACTS.
NOTE: Do not use the pressures from the unit's SERVICE
FACTS to determine the unit refrigerant charge. The correct
charge is shown on the unit nameplate. To charge the system
accurately, weigh in the charge according to the unit nameplate.

Voltage Check

With the compressor operating, check the line voltage at the unit
(contactor is located behind the Control access panel). The voltage
should be within the range shown on the unit nameplate. If low
voltage is encountered, check the size and length of the supply line
from the main disconnect to the unit. The line may be undersized
for the length of the run.

Cooling Shut Down

Set the comfort control to OFF or to a setting above room temperature.
IMPORTANT: De-energize the main power disconnect ONLY when
servicing the unit. Power may be required to keep the heat pump
compressor warm and to boil off refrigerant in the compressor.
WARNING
CAUTION
Page 25