Carrier FA4ANF Service Manual

In heat pump applications, the G signal is present in both coolingand heating modes, permitting EAC to be controlled from G signalonly. For this application, a user-supplied 24-vac relay can bedriven by G terminal eliminating need for relay kit.FK4B DE-HUMIDIFY MODENOTE: Humidistat must open on humidity rise.Latent capacities for systems using the FK4B Fan Coil are betterthan average systems. If increased latent capacity is an applicationrequirement, the FK4B can be wired to provide this requirement byadjusting its airflow in response to standard humidistat input. Fig.22 illustrates the wiring connections to activate de-humidify mode.Carefully consult product airflow data for cooling and dehumidi-fying mode.FK4C, FV4A, and 40FKAThe FK4C, FV4A, and 40FKA are similar to the discontinuedFK4B as they have both integrated controls and motor (ICM2) andtheir own special circuit board. The difference is in the software ofthe ICM2. Adjustments have been made in the CFM to enhance thedifferent modes of operation, such as, increased dehumidification.Set up of desired airflow is obtained by the selections made onEasy Select circuit board. The motor delivers requested airflow asdefined by signals received from Easy Select Board and the ICM2software programming.If a Thermidistat is used, additional CFM adjustments are madethrough the ICM2 for super dehumidification in cooling mode. The40FKA is shipped with the Thermidistat and will have anadditional CFM adjustment in heating mode called Comfort Heat.Under certain outdoor conditions in heating, the CFM will lowercausing an increase in air discharge temperature for comfortpurposes.Unlike fan coils using induction motors where static pressureaffects airflow, the FK4C, FV4A, and 40FKA are constant airflowunits. The blower delivers requested airflow regardless of staticpressure. Consult FK4C, FV4A, and 40FKA Product Data forstatic pressure limits. The ICM2 is pre-programmed and containsairflow tables for all modes of operation. Blower characteristics(requested airflow, torque, and speed) are known from laboratorytesting. If any 2 characteristics are known, the third is defined.Requested airflow is known from Easy Select board configurationand thermostat signals. Torque is known because it is directlyrelated to stator current which is measured by motor control. Speedis measured by counting back EMF pulses from stator windings.This information is entered into an expression which calculatestorque from speed and airflow numbers. If calculation does notmatch stored blower characteristics, torque is adjusted untilagreement is reached. This calculation and adjustment is per-formed every 0.8 sec while motor is in operation. There is no directmeasure of static pressure, but unit does react to a change in staticto maintain constant airflow. A change in pressure will result in achange in stator speed and torque. The motor will begin to adjuston the next sampling, calculate new desired speed and torque, andadjust as necessary.Step 9—Integrated Controls and Motor (ICM2)An ICM2 is fed high voltage AC power through the 5-pinconnector. (See Fig. 23.) The AC power is then rectified to DC bya diode module. After rectification, DC signal is electronicallycommunicated and fed in sequential order to 3 stator windings.The frequency of these commutation pulses determines motorspeed. The rotor is permanently magnetized.An ICM2 is powered with high voltage at all times. The motor willrun with high voltage alone. Low voltage must be applied tocontrol plug to run motor.Fig. 20—Mounting KFAIR0101ACR Relay KitA93216MOUNT FLUSH WITHTHESE TWO EDGESFig. 21—KFAIR0101ACR Relay KitWiring SchematicA9862524 VAC RELAYFAN COIL 230 VAC OR115 VAC BRANCH CKTAUX1(C) AUX2(G) GND HOT NEUTGRNBLKWHTNOCOM BLKBLKREDREDWHTTO EACFig. 22—Humidistat Wiring for De-Humidify ModeA93215HUMIDISTATTO PCB TERMINALMARKED 'RED'RED WIREFROM ICM2MOTORHUMIDISTAT WIRING FORDE-HUMIDIFY MODE28