Carrier 48TCA04---A12 Service And Maintenance Instructions

61To determine the minimum position setting, perform thefollowing procedure:1. Calculate the appropriate mixed air temperatureusing the following formula:(TO xOA ) + (TR x RA ) =TM100 100TO = Outdoor-Air TemperatureOA = Percent of Outdoor AirT R = Return-Air TemperatureRA = Percent of Return AirT M = Mixed-Air TemperatureAs an example, if local codes require 10% outdoorair during occupied conditions, outdoor-airtemperature is 60_F, and return-air temperature is75_F.(60 x .10) + (75 x .90) = 73.5_F2. Disconnect the supply air sensor from terminals Tand T1.3. Ensure that the factory-installed jumper is in placeacross terminals P and P1. If remote damperpositioning is being used, make sure that theterminals are wired according to Fig. 59 and that theminimum position potentiometer is turned fullyclockwise.4. Connect 24 vac across terminals TR and TR1.5. Carefully adjust the minimum positionpotentiometer until the measured mixed airtemperature matches the calculated value.6. Reconnect the supply air sensor to terminals T andT1.Remote control of the EconoMi$er IV damper is desirablewhen requiring additional temporary ventilation. If afield-supplied remote potentiometer (Honeywell partnumber S963B1128) is wired to the EconoMi$er IVcontroller, the minimum position of the damper can becontrolled from a remote location.To control the minimum damper position remotely,remove the factory-installed jumper on the P and P1terminals on the EconoMi$er IV controller. Wire thefield-supplied potentiometer to the P and P1 terminals onthe EconoMi$er IV controller. (See Fig. 81.)Damper MovementDamper movement from full open to full closed (or viceversa) takes 21 / 2 minutes.ThermostatsThe EconoMi$er IV control works with conventionalthermostats that have a Y1 (cool stage 1), Y2 (cool stage2), W1 (heat stage 1), W2 (heat stage 2), and G (fan). TheEconoMi$er IV control does not support spacetemperature sensors. Connections are made at thethermostat terminal connection board located in the maincontrol box.Occupancy ControlThe factory default configuration for the EconoMi$er IVcontrol is occupied mode. Occupied status is provided bythe black jumper from terminal TR to terminal N. Whenunoccupied mode is desired, install a field--suppliedtimeclock function in place of the jumper between TR andN. When the timeclock contacts are closed, theEconoMi$er IV control will be in occupied mode. Whenthe timeclock contacts are open (removing the 24--v signalfrom terminal N), the EconoMi$er IV will be inunoccupied mode.Demand Control Ventilation (DCV)When using the EconoMi$er IV for demand controlledventilation, there are some equipment selection criteriawhich should be considered. When selecting the heatcapacity and cool capacity of the equipment, themaximum ventilation rate must be evaluated for designconditions. The maximum damper position must becalculated to provide the desired fresh air.Typically the maximum ventilation rate will be about 5 to10% more than the typical cfm required per person, usingnormal outside air design criteria.A proportional anticipatory strategy should be taken withthe following conditions: a zone with a large area, variedoccupancy, and equipment that cannot exceed the requiredventilation rate at design conditions. Exceeding therequired ventilation rate means the equipment cancondition air at a maximum ventilation rate that is greaterthan the required ventilation rate for maximumoccupancy. A proportional-anticipatory strategy will causethe fresh air supplied to increase as the room CO2 levelincreases even though the CO2 setpoint has not beenreached. By the time the CO2 level reaches the setpoint,the damper will be at maximum ventilation and shouldmaintain the setpoint.In order to have the CO2 sensor control the economizerdamper in this manner, first determine the damper voltageoutput for minimum or base ventilation. Base ventilationis the ventilation required to remove contaminants duringunoccupied periods. The following equation may be usedto determine the percent of outside air entering thebuilding for a given damper position. For best results thereshould be at least a 10 degree difference in outside andreturn-air temperatures.(TO xOA ) + (TR x RA ) =TM100 100TO = Outdoor-Air TemperatureOA = Percent of Outdoor AirT R = Return-Air TemperatureRA = Percent of Return AirT M = Mixed-Air TemperatureOnce base ventilation has been determined, set theminimum damper position potentiometer to the correctposition.The same equation can be used to determine the occupiedor maximum ventilation rate to the building. For example,an output of 3.6 volts to the actuator provides a baseventilation rate of 5% and an output of 6.7 volts providesthe maximum ventilation rate of 20% (or base plus 15 cfmper person). Use Fig. 82 to determine the maximumsetting of the CO2 sensor. For example, an 1100 ppmsetpoint relates to a 15 cfm per person design. Use the1100 ppm curve on Fig. 82 to find the point when the CO2sensor output will be 6.7 volts. Line up the point on the48TC