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

Table 17 — Air Quantity LimitsUNIT48EJ,EK,EW,EYMINIMUM HEATINGAIRFLOW(Low Heat)MINIMUM HEATINGAIRFLOW(High Heat)MINIMUM COOLINGAIRFLOW (VAV)AT FULL LOADOPERATIONMINIMUM COOLINGAIRFLOW (CV)MAXIMUMAIRFLOW024 5730 5950 2000 6,000 10,000028 5730 5950 2500 7,500 12,500030 5730 5950 2750 8,250 13,750034 5730 5950 3000 9,000 15,000038 7360 9820 3500 10,500 17,500044 7360 9820 4000 12,000 20,000048 7360 9820 4500 13,500 22,500LEGENDCV — Constant VolumeVAV — Variable Air VolumeReturn-Air Filters — Check that correct filters are in-stalled in filter tracks (see Table 1). Do not operate unit with-out return-air filters.Filter Replacement — To replace filters, open filter ac-cess door (marked with label). Remove inner access panel.Remove plastic filter retainer in between filter tracks by slid-ing and pulling outward. Remove first filter by sliding it outof the opening in filter track. Locate filter removal tool, whichis shipped next to the return air dampers. Use the filter re-moval tool to remove the rest of the filters.Outdoor-Air Inlet Screens — Outdoor-air inlet screensmust be in place before operating unit.Economizer Adjustment — Remove filter access panel.Check that outdoor-air damper is closed and return-air damperis open.Economizer operation and adjustment are described inSequence of Operation section on this page; and MinimumDamper Position Setting section on page 24.Gas Heat — Verify gas pressures before turning on heatas follows:1. Turn off field-supplied manual gas stop, located externalto unit.2. Connect pressure gage to supply gas tap, located on field-supplied manual shutoff valve (see Fig. 13 on page 13).3. Connect pressure gage to manifold pressure tap on unitgas valve.4. Supply gas pressure must not exceed 13.5 in. wg. Checkpressure at field-supplied shut-off valve.5. Turn on manual gas stop and initiate a heating demand.Jumper R to W1 in the control box to initiate heat. OnVAV units, the RAT (Return-Air Temperature) must beless than or equal to 68 F for heating to be energized. Usethe field test procedure to verify heat operation. After theunit has run for several minutes, verify that incoming pres-sure is 5.0 in. wg or greater, and that the manifold pres-sure is 3.5 in. wg. If manifold pressure must be adjusted,refer to Gas Valve Adjustment section on page 47.Sequence of OperationNOTE: Unit is shipped with default values that can be changedthrough Service Tool, Building Supervisor, or Comfort-Works™ software. See Table 18 for default values.COOLING, CONSTANT VOLUME (CV) UNITS — Onpower up, the control module will activate the initializationsoftware of the control board. The initialization software then-reads DIP switch no. 1 position to determine CV or VAVoperation. Next, DIP switch no. 2 is read to determine if thecontrol is thermostat or sensor type operation. If switch 2 isopen,then sensors are employed. If switch no. 2 is closed,thermostat is employed. Initialization clears all alarms andalerts, remaps the input/output database for CV operation,sets maximum heat stages to 2, and sets maximum cool stagesto 3. The control reads DIP switch no. 3 and if open, then itsets the internal flag for expansion mode operation.The first time power is sent to the control board after apower outage, power up takes 5 minutes plus a random 1 to63 seconds.The TSTAT function performs a thermostat based controlby monitoring Y1, Y2, W1, W2, and G inputs. These func-tions control stages cool1, cool2, heat1, heat2, and indoorfan, respectively. If TSTAT function is NOT selected, thecontrol determines the occupancy state on the Time Sched-ules or with remote occupied/unoccupied input. If tempera-ture compensated start is active, the unit will be controlledas in the Occupied mode. User-defined set points are shownin Table 18.The occupied or unoccupied comfort set points must beselected and the space temperature offset input will be used,if present. The Occupied Heat set point default value is68 F. The Occupied Cool set point default value is 78 F. TheUnoccupied Heat set point default value is 55 F. The Un-occupied Cool set point value is 90 F. The control board willset appropriate operating mode and fan control. The controlboard will turn on indoor fan, if in Occupied mode, or de-termine if unit is in Unoccupied mode and the space tem-perature is outside of the unoccupied comfort set points,(Unoccupied Heat or Unoccupied Cool).The control board will then monitor space temperature againstcomfort set points and control heating or cooling stages asrequired. If system is in the Occupied mode, the economizerwill operate as required. If the system is in Unoccupiedmode, the system will perform nighttime free cool and IAQ(indoor air quality) pre-occupancy purge as required (whenfunctions are enabled via software). Whenever the DX(di-rect expansion) cooling is requested, the outdoor fan willoperate.The control board will operate economizer, run diagnos-tics to monitor alarms/alerts at all times, and respond to CCNcommunications to perform any configured network POC(product outboard control) functions such as time and outdoor-air temperature broadcast and Global occupancy broadcast.When the optional expansion I/O board is employed, it will:perform periodic scan and maintain database of expandedI/O points, perform Fire/Smoke control (power exhaust re-quired); and if in Occupied mode perform IAQ control andmonitor fan, filter, demand limit, and field-applied status (withaccessories).If thermostats are used to energize the G input, the controlwill turn on indoor fan without delay and open economizerdampers to minimum position.39