Carrier 48TC*D08 appendix Supplemental Controls, PremierLinkt Control

48TC

DCV operation is available in Occupied and Unoccupied periods with EconoMi$er IV. However, a control modification will be required on the 48TC unit to implement the Unoccupied period function.

Supplemental Controls

Compressor Lockout Relay (CLO) - The CLO is available as a factory-installed option or as a field-installed accessory. Each compressor has a CLO. The CLO compares the demand for compressor operation (via a 24-v input from Y at CLO terminal 2) to operation of the compressor (determined via compressor current signal input at the CLO’s current transformer loop); if the compressor current signal is lost while the demand input still exists, the CLO will trip open and prevent the compressor from restarting until the CLO has been manually reset. In the lockout condition, 24-v will be available at terminal X. Reset is accomplished by removing the input signal at terminal 2; open the thermostat briefly or cycle the main power to the unit.

Phase Monitor Relay (PMR) - The PMR protects the unit in the event of a loss of a phase or a reversal of power line phase in the three-phase unit power supply. In normal operation, the relay K1 is energized (contact set closed) and red LED indicator is on steady. If the PMR detects a loss of a phase or a phase sequence reversal, the relay K1 is energized, its contact set is opened and unit operation is stopped; red LED indicator will blink during lockout condition. Reset of the PMR is automatic when all phases are restored and phase sequence is correct. If no 24-v control power is available to the PMR, the red LED will be off. Smoke Detectors - Factory-installed smoke detectors are discussed in detail starting on page 17.

PremierLinkt Control

THERMOSTAT MODE — If the PremierLink controller is configured for Thermostat mode (TSTAT), it will control only to the thermostat inputs on J4. These inputs can be overridden through CCN communication via the CV_TSTAT points display table. When in this mode, the fire safety shutdown (FSD) input cannot be used, so any fire/life safety shutdown must be physically wired to disable the 24 vac control circuit to the unit.

Indoor Fan — The indoor fan output will be energized whenever there is 24 vac present on the G input. The indoor fan will be turned on without any delay and the economizer damper will open to its minimum position if the unit has a damper connected to the controller. This will also occur if the PremierLink controller has been configured for electric heat or heat pump operation.

Cooling — For cooling operation, there must be 24 vac present on G. When G is active, the PremierLink controller will then determine if outdoor conditions are suitable for economizer cooling when an economizer damper is available. A valid OAT, SPT (CCN space temperature) and SAT (supply air temperature) sensor MUST be installed for proper economizer operation. It recommended that an outdoor or differential enthalpy sensor also be installed. If one is not present, then a jumper is needed on the ENTH input on J4, which will indicate that the enthalpy will always be low. Economizer operation will be based only on outdoor air dry bulb temperature. The conditions are suitable when: enthalpy is low, OAT is less than OATL High Lockout for TSTAT, and OAT is less than OATMAX, the high setpoint for free cooling. The default for OATL is 65_F. The default for OATMAX is 75_F.

When all of the above conditions are satisfied and all the required sensors are installed, the PremierLink controller will use the economizer for cooling. One of three different control routines will be used depending on the temperature of the outside air. The routines use a PID loop to control the SAT to a supply air setpoint (SASP) based on the error from setpoint (SASPSAT). The SASP is determined by the routine.

If an economizer is not available or the conditions are not met for the following economizer routines below, the compressors 1 and 2 will be cycled based on Y1 and Y2 inputs respectively.

Any time the compressors are running, the PremierLink controller will lock out the compressors if the SAT becomes too low. These user configurable settings are found in the SERVICE configuration table:

Compressor 1 Lockout at SAT < SATLO1 (50 to 65_F) (default is 55_F)

Compressor 2 Lockout at SAT < SATLO2 (45 to 55_F) (default is 50_F)

After a compressor is locked out, it may be started again after a normal time-guard period and the supply-air temperature has increased at least 8_F above the lockout setpoint.

Routine No. 1: If the OAT ≤ DXLOCK (OAT DX lockout temperature) and DX Cooling Lockout is enabled when Y1 input is energized, the economizer will be modulated to maintain SAT at the Supply Air Setpoint (SASP) = SATLO1 + 3_F (Supply Air Low Temp lockout for compressor 1). When Y2 is energized, the economizer will be modulated to control to a lower SASP = SATLO2

+3_F (Supply Air Low Temp lockout for compressor no.

2). Mechanical cooling is locked out and will not be energized.

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