Carrier 69NT40-511-1, 69NT40-521 Condenser Pressure Control CPC, Controller Temperature Control

3.1.6Condenser Pressure Control (CPC)

A pressure control system has been incorporated by means of a condenser pressure transducer (CPT) and condenser pressure control (CPC) logic to maintain discharge pressures above 130 psig in low temperatures.

In order for the CPC logic to be enabled, the following conditions must be met:

SCPC configuration variable set to “In”

SCPT sensor is valid (alarm code AL68 inactive)

SAMBS sensor is valid (alarm code AL57 inactive)

SAMBS is less than or equal to 26.6_C (79.9_F)

SVoltage/Frequency ratio is less than or equal to 8.38

When condenser pressure control (CPC) is enabled (all of the above conditions are met), either pressures or timers may dictate a change of state from OFF to ON, or ON to OFF. If the condenser fan is OFF, it will be energized if saturation condensing pressure is greater than 200 psig OR if the condenser fan has been OFF for a maximum of sixty seconds depending on the ambient temperature. If the condenser fan is ON, it will de-energize only if the saturation condensing pressure is less than 130 psig and the condenser fan has been running for a minimum of thirty seconds depending on the ambient temperature. As the ambient temperature increases, the amount of time that the condenser fan is energized will correspondingly increase.

If any one of the following conditions occur the CPC logic will be disabled:

SCPT sensor is invalid (alarm code AL68 activates)

SAMBS sensor is invalid (alarm code AL57 activates)

SAMBS is greater than 29.5_C (85.1_F)

SVoltage/Frequency ratio is greater than 8.42

3.1.7Controller Temperature Control

There are two control ranges, Frozen and Perishable (chill). The Frozen range is active with set points at or below -10_C (+14_F), or -5_C (+23_F) optionally, and the Perishable range is active at set points above -10_C (+14_F), or -5_C (+23_F) optionally. See Figure 3-4 and Figure 3-5.

The Controller configuration variable for “Heat Lockout” (refer to Table 3-1) can be changed for set points of either -10_C (+14_F), or -5_C (+23_F) optionally.

NOTES

SWhen upward set point changes are made at ambients below 27_C (80_F), the compressor is immediately cycled OFF. The compressor three minute time delay will be overridden, so that as soon as the control temperature is at least 0.2_C (0.4_F) above set point the compressor will turn ON.

SWhen the compressor starts for the first time after power is applied manually, the SMV will open to 100% and the unit will run for three minutes to boil off dissolved refrigerant from the compressor oil.

3.1.7.1Perishable (Chill) Range Above --10_C (+14_F), or --5_C (+23_F) Optionally.

For set points above -10_C (+14_F), or -5_C (+23_F) optionally, the Controller maintains SUPPLY air at the set temperature by the following modes of operation:

a.Operation in the conventional mode without dehumidification (Code 33 OFF)

1.At ambients below 27_C (80_F), the condenser fan will cycle on/off depending on condenser pressure and on/off times.

If the condenser pressure is greater than 200 psig OR the condenser fan has been OFF at least 60 seconds, the condenser fan will start.

If the condenser pressure is less than 130 psig AND the condenser fan remains ON for at least 30 seconds, the condenser fan will stop.

2.At ambients above 27_C (80_F), condenser pressure control (CPC) is disabled and the condenser fan runs continuously.

If the unit starts when ambient is below -10_C (+14_F) and condenser pressure is below 200 psig, the condenser fan will not start until pressure reaches 200 psig.

The supply probe is used for control and is so indicated by the “SUPPLY” LED on the display module. The Perishable temperature range demands high accuracy. The unit is capable of maintaining supply air temperature to within ¦0.25_C (¦0.5_F) of the set point temperature setting. In Perishable range above -10_C (+14_F), or -5_C (+23_F) optionally, control is maintained by controlling the positions of the suction

T-268-07 3-14