Controls, Start-Up, Operation, Service and ... - Climayoreo

Alarms and Alarm History for for any unresolved alarm codes
and correct. Verify Humidi-MiZer configuration settings are
correct for the site requirements. If alarm conditions are corrected
and cleared, then operation of the compressors, fans, and
Humidi-MiZer valves may be verified by using the Service
Test mode. See page 35. In addition to the Cooling Service
Analysis (Table 71), see the Humidi-MiZer Service Analysis
(Table 72) for more information.
Thermistor Troubleshooting — The OAT, SAT,
RAT, CCT, T55, T56, and T58 temperature sensors use 10K
thermistors. Resistances at various temperatures are listed in
Tables 75 and 76. The DTT uses an 86K thermistor. See Table
77. The RGTA uses a 5K thermistor. See Tables 78 and 79.
THERMISTOR/TEMPERATURE SENSOR CHECK — A
high quality digital volt-ohmmeter is required to perform this
check.
1. With the unit powered down, remove the terminal strip of
the thermistor being diagnosed from the appropriate control
board (MBB-J8 or RCB-J6). Connect the digital
LEGEND
CB — Circuit Breaker
TXV — Thermostatic Expansion Valve
Table 71 — Cooling Service Analysis
91
ohmmeter across the appropriate thermistor terminals in
the terminal strip.
2. Using the resistance reading obtained, read the sensor
temperature from the appropriate sensor table.
3. To check thermistor accuracy, measure the temperature at
the thermistor location with an accurate thermocouple–
type temperature measuring instrument. Insulate thermocouple
to avoid ambient temperatures from influencing
reading. The temperature measured by the thermocouple
and the temperature determined from the thermistor resistance
reading should be within 5° F (3° C) if care was taken
in applying thermocouple and taking readings.
If a more accurate check is required, unit must be powered
down and thermistor removed and checked at a known temperature
(freezing point or boiling point of water) by measuring
the resistance of the thermistor with the terminal strip removed
from the control board. With the terminal strip plugged back
into the control board and the unit powered up, compare the
temperature determined from the resistance measurement with
the value displayed by the control in the Temperatures menu
using the scrolling marquee display.
PROBLEM CAUSE REMEDY
Compressor and Fan Will Not Power failure. Call power company.
Start.
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 ComfortLink scrolling marquee.
Thermostat or occupancy schedule set point not calling
for Cooling.
Check using ComfortLink scrolling marquee.
Outdoor temperature too low. Check Compressor Lockout Temperature (MC.LO)
using ComfortLink scrolling marquee.
Active alarm. Check active alarms using ComfortLink scrolling
marquee.
Compressor Cycles (Other Than Insufficient line voltage. Determine cause and correct.
Normally Satisfying Thermostat). Active alarm. Check active alarms using ComfortLink scrolling
marquee.
Compressors Operates
Unit undersized for load. Decrease load or increase of size of unit.
Continuously.
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 returnair
temperature).
Reset thermostat or occupancy schedule.