4
Refer to Product Data for recommended fuse sizes. When making
electrical connections, provide clearance at the unit for refrigerant
piping connections.
NOTE
: The 538A units use the control transformer supplied with
the matched indoor unit.
Power Wiring
Unit is factory wired for voltage shown on nameplate. Provide
adequate, fused disconnect switch within sight from unit, readily
accessible, but out of reach of children. Provision for locking the
switch open (off) is advisable to prevent power from being turned
on while unit is being serviced.
Disconnect switch, fuses, and field wiring must comply with the
NEC and local code requirements. Use copper wire only between
the disconnect switch and unit. Use minimum 75 C wire for the
field power connection.
Route power wires through the opening in unit side panel and
connect in the unit control box as shown on the unit label diagram.
Unit must be grounded.
Connections to Duct Free Fan Coil Units
The 538A units are designed for easy match--up to 619C duct free fan
coils. This unit provides 24 v power for the outdoor unit from the fan
coil. Connect the Y and C terminals of the indoor unit to the Y and C
terminals.
START--UP
Step 1
—
Preliminary Checks
1. Check that all internal wiring connections are tight and that
all barriers, covers, and panels are in place.
2. Field electrical power source must agree with unit name-
plate rating.
3. All service valves must be open.
4. Belly--band crankcase heater must be tight on compressor
crankcase for those units with belly--band heaters.
Step 2
—
Evacuate and Dehydrate
Field piping and fan coil must be evacuated and dehydrated.
Step 3
—
Charge System
Release charge into system by opening (backseating) liquid and
suction line service valves.
Step 4
—
To Start Unit
Be sure that the field disconnect is closed. Set room thermostat
below ambient temperature. Operate unit for 15 minutes, then
check system refrigerant charge. See Refrigerant Charging section
of this document.
NOTE
: When using in conjunction with 619C fan coils, refer to
start--up instructions included with fan coil for correct start--up
procedures.
SERVICE
!
WARNING
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Before installing, modifying, or servicing system, main
electrical disconnect switch must be in the OFF position.
There may be more than 1 disconnect switch. Lock out and
tag switch with a suitable warning label.
Outdoor Fan
A reinforced wire mount holds the outdoor fan assembly in
position. See Fig. 5 for proper mounting position.
538A Unit Size, in. (mm)
018,024
030,036
048,060
0.433 (11.00)
0
0
A07401
Fig. 5
---
Condenser Fan Mounting Positions
High--Pressure Relief Valve
The high--pressure relief valve is located in the compressor. The
relief valve opens at a pressure differential of approximately 550 to
625
±
50 psig between suction (low side) and discharge (high side)
to allow pressure equalization.
Internal Current and Temperature Sensitive Overload
The control resets automatically when internal compressor motor
temperature drops to a safe level (overloads may require up to 45
minutes to reset). When an internal overload is suspected of being
open, check by using an ohmmeter or continuity tester.
Pumpdown Procedure
The system may be pumped down in order to make repairs on the
low side without losing complete refrigerant charge.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
Never open system to atmosphere while it is under a vacuum.
Equipment damage may result.
When system must be opened for service, recover refrigerant, break
vacuum with dry nitrogen before opening system.
1. Attach pressure gage to suction service valve gage port.
2. Frontseat the liquid/mixed phase line valve.
3. Start unit and run until suction pressure reaches 20 psig.
4. Shut unit off and frontseat suction valve.
5. De--pressurize low side of unit and recover refrigerant fol-
lowing accepted practices.
High--Pressure Switch
The high--pressure switch, located on discharge line, protects
against high discharge pressures caused by such events as
overcharge, condenser--fan motor failure, system restriction, etc. It
opens on pressure rise at about 650
±
10 psig. If system pressures
go above this setting during abnormal conditions, the switch
opens.
!
WARNING
PERSONAL INJURY HAZARD
Failure to follow this warning could result in personal
injury or death.
DO NOT
attempt to simulate these system abnormalities --
high pressures pose a serious safety hazard.
The high--pressure switch is checked with an ohmmeter. If system
pressure is below 625 psig switch shows continuity.
538A
