Carrier SINGLE PACKAGE ROOFTOP UNITS ELECTRIC COOLING/GAS HEATING 48EJ Installation And Service Instructions Manual

Also see for 48EJ: Installation, Start-Up and Service Instructions User manual

Contents

To set the VFD, the VFD must be powered up; however,since it is located near the indoor air fan, operation of thefan is not desirable. To disable the fan, perform the follow-ing procedure:1. Open the indoor fan circuit breaker.2. Remove the jumper between CC and ST on the terminalstrip of the VFD (see Fig. 41).3. Close the indoor fan circuit breaker. The VFD now ispowered but the fan will not operate.4. On the front of the VFD is a keypad and display whichwill be used to enter the set point. To access this field,press the ‘‘PRG’’ key until the display reads ‘‘S.PrG’’(Speed Group Parameters). Press the arrow key until ‘‘Sr1’’is displayed. This is the VFD set point listed in Table 7.5. Press the ‘‘READ/WRITE’’ key. The set point value willbe displayed. Use the up-arrow or down-arrow key toadjust the set point value to the value desired.6. Press the ‘‘READ/WRITE’’ key again to enter the newvalue.7. Check the factory default values.IMPORTANT: The Carrier factory default valuesfor the VFD may be different than the default val-ues of the manufacturer. Refer to the Carrier lit-erature when checking default values. The followingdefault values have been changed from the manu-facturer settings to more closely match the VFDoperation to a Carrier VAV unit.SETUP PARAMETERS (Item 6, Point 1, Output Fre-quency) — The default value should be 20.JUMP FREQUENCY GROUP (Item 7, PID Set PointControl Select) — The default value is 1.JUMP FREQUENCY GROUP (Item 8, Proportional Gain)— The default value is 100.JUMP FREQUENCY GROUP (Item 9, Integral Gain)— The default value is 50.SPEED GROUP PARAMETERS (Item 2, Multi-SpeedRun Frequency No. 1) — The factory setting is 30.SPEED GROUP PARAMETERS (Item 2, Fire SpeedOverride Frequency) — The factory setting is 60.8. Open the indoor fan circuit breaker.9. Replace the jumper between CC and ST on the terminalstrip of the VFD.10. Close the indoor fan circuit breaker; the VFD now ispowered and the fan will operate.NOTE: Any field measurement of supply fan amps must betaken with an RMS meter between the fan circuit breakerand fan contactor (upstream of VFD).Power Exhaust — The optional non-modulating powerexhaust (CV only) is a two-stage design where the operationof the exhaust fans is linked to economizer position. Whenthe supply fan is running and the economizer is 25% open,the base module closes contacts, activating two exhaust fans.When the economizer position reaches 75% open, the basemodule activates the other two exhaust fans. The fans willturn off when the economizer closes below the same points.The economizer position set points that trigger the exhaustfans can be modified, but only through use of the ServiceTool, Comfort Works, or Building Supervisor software. Ifsingle-stage operation is desired, adjust the economizer setpoints to identical values at the desired point to activate allexhaust fans.The optional modulating power exhaust (VAV standard,CV optional) is controlled by a modular electronic se-quencer system. This system consists of a model R353 sig-nal input module and 4 model S353 staging modules. Thesignal input module receives a 0 to 10 vdc signal from thebuilding pressure transducer, which is mounted adjacent tothe supply static transducer behind the filter access panel.The modules are mounted just below the unit control board.The left module is the R353, and the 4 modules on the rightare S353 modules for stages 1 through 4. On the unit wiringlabel, the R353 is designated PESC, and the S353 modulesare designated PES1 through PES4.The building pressure transducer range is −0.5 to+ 0.5 in. wg. It is powered by a 0 to 10 vdc signal. A factory-installed hose at the ‘‘Lo’’ connection leads to atmosphere,and a field-supplied hose must be connected to the ‘‘Hi’’ con-nection and led into the building to a point where buildingpressure is to be controlled (positive-pressure building). Thereis a plug button in the bulkhead just above the transducers,for use in leading the hoses into the building via the returnair ductwork.There are 3 adjustments at the R353 module, all of whichhave been factory set. In the center of the circuit board isa set of 4 pins with a jumper, labeled J2. This determines themode of operation. The bottom two pins must be jumperedfor direct operation. Direct operation means that the stag-ing modules are activated in sequence as the input signalincreases.Table 7 — VFD Supply Air Pressure Set PointPRESSURE(in. wg)CONTROL(mA)VFDSET POINT0 4.0 00.25 4.8 30.50 5.6 60.75 6.4 91.00 7.2 121.25 8.0 151.50 8.8 181.75 9.6 212.00 10.4 242.25 11.2 272.50 12.0 302.75 12.8 333.00 13.6 363.25 14.4 393.50 15.2 42VFD — Variable Frequency Drive(SS2) (SS3)FLA FLB FLC P24 RCH LOW FM AM PP RR IV CC ST F R CC SS1 JOG AD2 RST CC+ –D P D P JUMPERSNOTE: Terminal strip is located inside the VFD at the bottom.Fig. 41 — VFD Factory-Installed Jumpers32