Carrier 38APS025 Manual page 170

• Check to be sure that the long line check valve assembly
is mounted correctly. The arrows indicate direction of
flow.
• Check the Discharge Pressure Transducer for accuracy.
P122 - Circuit A High Pressure Trip Pre-Alert
P123 - Circuit B High Pressure Trip Pre-Alert
T122 - Circuit A High Pressure Trip
T123 - Circuit B High Pressure Trip
Criteria for Trip: This alert has multiple criteria. The Main
Base Board (MBB) monitors the HPS (high pressure switch).
The 38AP units employ one HPS for each circuit. For High
Pressure Trip Pre-Alert and Alert:
1. The alarm criterion is checked when the circuit is ON or
OFF.
2. The circuit HPS opens for 4 seconds or more.
If all of the conditions listed above are true a pre-alert (P122/
P123) will be generated for the first two occurrences. This is a
non-broadcast alert. The third occurrence will result in the alert
(T122/T123). If the circuit runs for 15 minutes without tripping
the pre-alert condition or if the circuit has cycled three times,
the strike counter is reset.
Action To Be Taken: The circuit shuts down immediately or is
not allowed to start.
Reset Method: The pre-alerts (P122/P123) will automatically
reset for the first two occurrences of this condition. After the
pre-alert is generated, there is a 15-minute time delay and the
high pressure switch must reset before the circuit will attempt
to restart. Following the second automatic reset of the pre-alert,
the next occurrence (T122/T123) will require a manual reset.
Possible Causes: If this condition is encountered, check the
following items:
• Check the wiring of the high pressure switch circuit.
• Check the wiring of the liquid line solenoid valve, if
equipped. Be sure that the correct valve operates for the
circuit.
• Check for non-condensables in the refrigerant circuit.
• Check for condenser air re-circulation.
• Check for the proper refrigerant charge (overcharged).
• Check for operation beyond the limit of the machine.
• Check the condenser coils for debris or restriction.
• Check the evaporator coil for a refrigerant restriction.
• For the TXV(s) (thermostatic expansion valves):
- Check for the proper TXV. The 38AP units require bleed
port TXVs. Failure to use this type of valve may result in
High Pressure Switch Trips at start-up.
- Check the TXV for proper operation.
• Check the condenser fans and motors for proper rotation
and operation.
• Check the liquid line service valve to be sure that it is
open.
• Check to be sure that the long line check valve assembly
is mounted correctly. The arrows indicate direction of
flow.
• Check the discharge pressure transducer for accuracy.
A126 - Circuit A High Head Pressure
T126 - Circuit A High Head Pressure
A127 - Circuit B High Head Pressure
T127 - Circuit B High Head Pressure
Criteria for Trip: The following conditions must be true:
1. The circuit is ON.
2. All outdoor fans for the circuit or all common outdoor
fans must be ON.
3. The compressor's operation is outside of the operating
envelope. See Fig. 156 and 157 on page 138 for the
compressor operating envelope, or see the following
calculations. These are shown graphically in Fig. 187 and
188.
a. If circuit saturated suction temperature is greater
than or equal to –20.0 F (–28.9 C) but less than
–10.0 F (–23.3 C) and circuit saturated condensing
temperature is greater than 2.5 times circuit satu-
rated suction temperature + 140.0 F (104.4 C).
b. If circuit saturated suction temperature is greater
than or equal to –10.0 F (–23.3 C) but less than
15.0 F (–9.4 C) and circuit saturated condensing
temperature is greater than circuit saturated suction
temperature + 125.0 F (69.4 C).
c. If circuit saturated suction temperature is greater
than or equal 15.0 F (–9.4 C) but less than 40.0 F
(4.4 C) and circuit saturated condensing tempera-
ture is greater than 0.4 times circuit saturated suc-
tion temperature + 134.0 F (63.8 C).
d. If circuit saturated suction temperature is greater
than or equal 40.0 F (4.4 C) but less than 45.0 F
(7.3 C) and circuit saturated condensing tempera-
ture is greater than circuit saturated suction tem-
perature + 110.0 F (61.1 C).
e. If circuit saturated suction temperature is greater
than or equal 45.0 F (7.3 C) and circuit saturated
condensing temperature is greater than 155.0 F
(68.3 C).
The first four daily occurrences of these conditions will gen-
erate a T126 or T127 alert for the appropriate circuit. With the
fifth daily occurrence, the condition will generate the A126 or
A127 alarm for the appropriate circuit.
Action To Be Taken: The circuit shuts down immediately.
Reset Method: For T126/T127, the alert will automatically
reset for the first 4 daily occurrences once the circuit saturated
condensing temperature falls below the trip criteria. The cir-
cuit will restart once the time guard has been satisfied. For
A126/A127, the alarm requires a manual reset.
Possible Causes: If this condition is encountered, check the
following items:
• Check for non-condensables in the refrigerant circuit.
• Check for condenser air re-circulation.
• Check for the proper refrigerant charge (overcharged).
• Check for operation beyond the limit of the machine.
• Check the condenser coils for debris or restriction.
• Check the evaporator coil for a refrigerant restriction.
• Check the TXV for proper operation.
• Check the condenser fans and motors for proper rotation
and operation.
• Check the liquid line service valve to be sure that it is
open.
• Check the suction and discharge pressure transducers for
accuracy.
• Confirm unit configuration.
170