Humidi-Mizer® System Troubleshooting - Carrier 48LC Series Controls, Start-Up, Operation And Troubleshooting

(LEN) RESISTANCE BETWEEN
PINS / CONNECTOR
DEVICE
Pins
1 to 3
19.92 KΩ
MBB
PROBLEM
Compressor and Fan
Will Not Start
Compressor Cycles (other than
normally satisfying thermostat)
Compressor Operates
Continuously
Excessive Condenser
Pressures
Condenser Fans Not Operating
Excessive Suction Pressure
Suction Pressure Too Low
LEGEND
TXV — Thermostatic Expansion Valve
Humidi-MiZer® System Troubleshooting
Use the SystemVu™ control display or a CCN device to view
the cooling status display and the cooling diagnostic display. See
"Optional Humidi-MiZer Dehumidification System" on page 21
for information on the cooling operation and the related Humidi-
MiZer system operation. Check the current alarms and alarm
history for any cooling alarm codes and correct any causes (see
Table 16 on page 38). Verify any unique control configurations
per installed site requirements or accessories.
Table 17 — Communication Resistances
Pins Pins
1 to 2 2 to 3
10.63 KΩ 9.51 KΩ 19.92 KΩ
Table 18 — Cooling Service Analysis
CAUSE
Power failure.
Fuse blown or circuit breaker tripped.
Disconnect off.
Compressor time guard to prevent short cycling. Check using SystemVu Display.
Thermostat or occupancy schedule set point not
calling for cooling.
Outdoor temperature too low.
Active alarm.
Insufficient line voltage.
Active alarm.
Unit undersized for load.
Thermostat or occupancy schedule set point too
low.
Dirty air filters.
Low refrigerant charge.
Condenser coil dirty or restricted.
Dirty condenser coil.
Refrigerant overcharge.
Faulty TXV.
Condenser air restricted or air short cycling.
Restriction in liquid tube.
No power to contactors.
High heat load.
Faulty TXV.
Refrigerant overcharged.
Dirty air filters.
Low refrigerant charge.
Faulty TXV.
Insufficient evaporator airflow.
Temperature too low in conditioned area (low
return-air temperature).
(BAS) RESISTANCE BETWEEN
PINS / CONNECTOR
Pins Pins Pins
1 to 3 1 to 2 2 to 3
10.63 KΩ 9.51 KΩ
Call power company.
Replace fuse or reset circuit breaker.
Power disconnect.
Check using SystemVu Display.
Check Compressor Lockout Temperature using SystemVu
Display.
Check active alarms using SystemVu Scrolling Marquee.
Determine cause and correct.
Check active alarms using SystemVu Scrolling Marquee.
Decrease load or increase size of unit.
Reset thermostat or schedule set point.
Replace filters.
Check pressure, locate leak, repair, evacuate, and
recharge.
Clean coil or remove restriction.
Clean coil.
Recover excess refrigerant.
1. Check TXV bulb mounting and secure tightly to suction
line and insulate.
2. Replace TXV (and filter drier) if stuck open or closed.
Determine cause and correct.
Remove restriction.
Fuse blown or plug at motor loose.
Check for sources and eliminate.
1. Check TXV bulb mounting and secure tightly to suction
line and insulate.
2. Replace TXV (and filter drier) if stuck open or closed.
Recover excess refrigerant.
Replace air filters.
Check pressure, locate leak, repair, evacuate, and
recharge.
1. Check TXV bulb mounting and secure tightly to suction
line and insulate.
2. Replace TXV (and filter drier) if stuck open or closed.
Check belt tension. Check for other restrictions.
Reset thermostat or occupancy schedule.
If alarm conditions are corrected and cleared, operation of the
compressors, fans, and Humidi-MiZer system valves may be
verified by using the Service Test mode (see Table 4 on
page 13). In addition to general cooling service analysis
(Table 18), see Table 19 on page 42 for general Humidi-MiZer
system service analysis.
NOTE: Wiring, operation, and charge are different on a Humidi-
MiZer system unit compared to a standard unit.
41
(RNET) RESISTANCE BETWEEN
PINS / CONNECTOR
Pins Pins
GND to + GND to -
2.25 KΩ 1 KΩ
REMEDY
Pins
+ to -
3.3 KΩ