86
determining the resistance with unit shut down and thermistor
disconnected from J8. Compare the values determined with the
value read by the control in the Temperatures mode using the
scrolling marquee display.
Transducer Troubleshooting —
The electronic con-
trol uses 2 suction pressure transducers to measure the suction
pressure of circuits A and B. The pressure/voltage characteris-
tics of these transducers are in shown in Tables 76 and 77. The
accuracy of these transducers can be verified by connecting an
accurate pressure gage to the second refrigerant port in the
suction line.
Table 71 — Cooling Service Analysis
LEGEND
PROBLEM CAUSE
REMEDY
Compressor and Fan Will Not
Start.
Power failure.
Call power company.
Fuse blown or circuit breaker tripped. Check CB1,
CB2, and CB3.
Replace fuse or reset circuit breaker.
Disconnect off.
Power disconnect.
Compressor time guard to prevent short cycling.
Check using
Comfort
Link™
scrolling marquee.
Thermostat or occupancy schedule set point not call-
ing for Cooling.
Check using
Comfort
Link
scrolling marquee.
Outdoor temperature too low.
Check Compressor Lockout Temperature (MC.LO)
using
Comfort
Link
scrolling marquee.
Active alarm.
Check active alarms using
Comfort
Link
scrolling
marquee.
Compressor Cycles (Other Than
Normally Satisfying Thermostat).
Insufficient line voltage.
Determine cause and correct.
Active alarm.
Check active alarms using
Comfort
Link
s
crolling
marquee.
Compressors Operates
Continuously.
Unit undersized for load.
Decrease load or increase of size of unit.
Thermostat or occupancy schedule set point too low. Reset thermostat or schedule set point.
Dirty air filters.
Replace filters.
Low refrigerant charge.
Check pressure, locate leak, repair evacuate, and
recharge.
Condenser coil dirty or restricted.
Clean coil or remove restriction.
Excessive Head Pressures.
Loose condenser thermistors.
Tighten thermistors.
Dirty condenser coil.
Clean coil.
Refrigerant overcharge.
Recover excess refrigerant.
Faulty TXV.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Condenser air restricted or air short cycling.
Determine cause and correct.
Restriction in liquid tube.
Remove restriction.
Condenser Fans Not Operating.
No Power to contactors.
Fuse blown or plug at motor loose.
Excessive Suction Pressure.
High heat load.
Check for sources and eliminate
Faulty TXV.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Refrigerant overcharged.
Recover excess refrigerant.
Suction Pressure Too Low.
Dirty air filters.
Replace air filters.
Low refrigerant charge.
Check for leaks, repair, and recharge.
Faulty TXV.
1. Check TXV bulb mounting and secure tightly to
suction line and insulate.
2. Replace TXV (and filter drier) if stuck open or
closed.
Insufficient evaporator airflow.
Check belt tension. Check for other restrictions.
Temperature too low in conditioned area (low return-
air temperature).
Reset thermostat or occupancy schedule.
CB
—
Circuit Breaker
TXV —
Thermostatic Expansion Valve
Summary of Contents for WEATHERMASTER 48Z030
Page 103: ...103 Fig 15 Typical Power Schematic Sizes 030 050 Shown a48 8408 ...
Page 104: ...104 Fig 16 Main Base Board Input Output Connections a48 8409 ...
Page 105: ...105 Fig 17 RCB ECB CEM SCB Input Output Connections a48 8410 ...
Page 106: ...106 Fig 18 Typical Gas Heat Unit Control Wiring 48Z055 105 Units Shown a48 8411 ...
Page 107: ...107 Fig 19 Typical Electric Heat Unit Control Wiring 50Z055 105 Units Shown a50 8248 ...
Page 108: ...108 Fig 20 Typical Power Wiring 115 V 48Z Units a48 8412 ...
Page 109: ...109 Fig 21 Typical Power Wiring 115 V 50Z Units a50 8249 ...
Page 110: ...110 Fig 22 Typical Gas Heat Section Size 055 105 Units Shown a48 8413 ...
Page 111: ...111 Fig 23 Component Arrangement Size 030 050 Units ...
Page 112: ...112 Fig 24 Component Arrangement Size 055 070 Units ...
Page 113: ...113 Fig 25 Component Arrangement Size 075 105 Units ...
