Carrier GEMINI 38APD025-100 Operating And Service Manual

Also see for GEMINI SELECT 38APD025: Installation instructions Manual Installation instructions

Carrier GEMINI 38APD025-100 Operating And Service Manual Manual pdf 23 page image

23Fan Status Input — A proof-of-fan operation is recom-mended and needs to be field installed in the indoor unit. Sev-eral different types of switches can be utilized, such as a differ-ential pressure switch located across the indoor fan or auxiliarycontacts on an indoor fan contactor.Thermostat Input — A two-stage thermostat can beused for constant volume applications to provide Y1 and Y2cooling inputs.Pressure Transducer Inputs — Each refrigerant cir-cuit is equipped with a suction and discharge pressure trans-ducer. The suction pressure transducers have a yellow bodywith a pressure range of -6.7 to 420 psig while the dischargetransducers have a red body with a pressure range of 14.5 to667 psig. These inputs connect to the MBB (main base board)and are used to monitor the status of the unit and to ensure theunit operates within the compressor envelope. The transducersare used to protect the compressor from operating at too low ortoo high of a pressure condition. In some cases, the unit maynot be able to run at full capacity. The MBB will automaticallyreduce the capacity of a circuit as needed to maintain specifiedmaximum/minimum operating pressures.Energy Management Module (Fig. 28) — Theenergy management module (EMM) is a factory-installed op-tion (FIOP) or field-installed accessory used for the followingtypes of temperature reset, demand limit, and capacity controlfeatures:• 4 to 20 mA temperature reset• 4 to 20 mA cooling set point• 4 to 20 mA desired capacity set point• 4 to 20 mA demand limit• Discrete inputs for 2-step demand limit (requires field-supplied dry contacts capable of handling a 24 vac,50 mA load)• Discrete inputs for units with dual thermostatsNOTE: A field-supplied 4 to 20 mA signal generator is re-quired for use with the EMM.See VAV Supply Air Temperature Reset and Demand Limitsections on pages 29 and 31 for further details.Control — When mechanical cooling is required, the MBBhas the capability to control the unit capacity by staging multi-ple scroll compressors and controlling the digital scroll com-pressor operation. The control also checks on various other op-eration parameters in the unit to make sure that safeties are notexceeded and the compressors are reliably operated.The ComfortLink™ control system offers two basic controlapproaches to mechanical cooling; constant volume operationfor 2 stages of cooling or VAV operation for multiple stagesof cooling. In addition to these methods of control, theComfortLink control offers the ability to run multiple stages ofcooling for either a space temperature sensor or thermostatcontrol by controlling the unit to either a low or high cool setpoint. The control type Configuration OPT2 C.TYP de-termines the selection of the type of cooling control as well asthe method for selecting a cooling mode.SETTING UP THE SYSTEMMachine Control Type (Configuration OPT2 C.TYP)— The most important cooling control configuration is locatedunder Configuration OPT2. This configuration defines themethod and control source responsible for selecting a coolingmode. The configuration also determines the method by whichcompressors are staged. Control types are:• C.TYP = 1 (VAV-RAT) configuration refers to standardVAV operation.CAUTIONCare should be taken when interfacing with other manufac-turer’s control systems due to possible power supplydifferences, full wave bridge versus half wave rectification.The two different power supplies cannot be mixed.ComfortLink™ controls use half wave rectification. Asignal isolation device should be utilized if a full wavebridge signal generating device is used.  CEBD430351-0396-01CTEST 1CEPL130351-01PWRTEST 2J1 J2J4 J3J5J6J7LENSTATUSRED LED - STATUS GREEN LED -LEN (LOCAL EQUIPMENT NETWORK) ADDRESSDIP SWITCHFig. 28 — Energy Management Module