74
Daylight Savings Stop Week (
DS.SP
→
SP.WK
) — This is
the stop week of the month for daylight savings. The week can
be set from 1 to 5.
Daylight Savings Stop Day (
DS.SP
→
SP.DY
) — This is the
stop day of the week for daylight savings. The day can be set
from 1 to 7 (Sunday=1, Monday=2, etc.).
Daylight Savings Minutes To Subtract (
DS.SP
→
MIN.S
) —
This is the amount of time that will be removed from the time
clock after daylight savings ends.
TROUBLESHOOTING
The Scrolling Marquee display shows the actual operating
conditions of the unit while it is running. If there are alarms or
there have been alarms, they will be displayed in either the cur-
rent alarm list or the history alarm list. The Service Test mode
allows proper operation of the compressors, fans, and other
components to be checked while the unit is not operating.
Complete Unit Stoppage —
There are several condi-
tions that can cause the unit not to provide heating or cooling.
If an alarm is active which causes the unit to shut down,
diagnose the problem using the information provided in
the Alarms and Alerts section on page 86, but also check for
the following:
• Cooling and heating loads are satisfied.
• Programmed schedule.
• General power failure.
• Tripped control circuit transformers circuit breakers.
• Tripped compressor circuit breakers.
• Unit is turned off through the CCN network.
Single Circuit Stoppage —
If a single circuit stops
incorrectly, there are several possible causes. The problem
should be investigated using information from the Alarms and
Alerts section on page 86.
Service Analysis —
Detailed service analysis can be
found in Tables 88-90 and in Fig. 12.
Restart Procedure —
Before attempting to restart the
machine, check the alarm list to determine the cause of the
shutdown. If the shutdown alarm for a particular circuit has
occurred, determine and correct the cause before allowing the
unit to run under its own control again. When there is problem,
the unit should be diagnosed in Service Test mode. The alarms
must be reset before the circuit can operate in either Normal
mode or Service Test mode.
Thermistor Troubleshooting —
The electronic con-
trol uses five 5K-thermistors for the saturated condensing
temperature sensor SCT.A and SCT.B. See Tables 91 and 92
for temperature vs. resistance data.
When replacing thermistors SDT.A and SDT.B, reuse the
original hardware. These thermistors must be clamped tightly
to the hairpins of the condenser.
The EDT, OAT, RAT, LAT, T55, T56, and T58 space tem-
perature sensors use 10K thermistors. Resistances at various
temperatures are listed in Tables 93 and 94.
THERMISTOR/TEMPERATURE SENSOR CHECK — A
high quality digital volt-ohmmeter is required to perform this
check.
1. Connect the digital voltmeter across the appropriate ther-
mistor terminals at the J8 terminal strip on the Main Base
Board.
2. Using the voltage reading obtained, read the sensor tem-
perature from Tables 91-94.
3. To check thermistor accuracy, measure temperature at
probe location with an accurate thermocouple-type
temperature-measuring instrument. Insulate thermocou-
ple to avoid ambient temperatures from influencing
reading. Temperature measured by thermocouple and
temperature determined from thermistor voltage reading
should be close, 5° F (3° C) if care was taken in applying
thermocouple and taking readings.
If a more accurate check is required, unit must be shut down
and thermistor removed and checked at a known temperature
(freezing point or boiling point of water) using either voltage
drop measured across thermistor at the J8 terminal, or by deter-
mining the resistance with unit shut down and thermistor dis-
connected 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 Table 95. The accuracy
of these transducers can be verified by connecting an accurate
pressure gage to the second refrigerant port in the suction line.
Summary of Contents for WEATHERMAKER 48AJ020
Page 95: ...95 Fig 13 Typical Main Control Box Wiring Schematic A48 7787 ...
Page 96: ...96 TO NEXT PAGE Fig 14 Auxiliary Control Box Wiring Schematic A48 7294 ...
Page 98: ...98 Fig 15 Typical 2 Stage Gas Heat Wiring Schematic Size 051 and 060 Units Shown A48 6866 ...
Page 102: ...102 TO NEXT PAGE Fig 18 Typical Power Schematic Size 051 and 060 Units Shown A48 7298 ...
Page 104: ...104 Fig 19 Controls Option Wiring Schematic A48 7810 ...
Page 105: ...105 Fig 20 Small Chassis Component Location Size 020 035 Units A48 7301 ...
Page 106: ...106 Fig 21 Large Chassis Component Locations Size 036 060 Units A48 7302 ...