Carrier EY024-048, 48EJ, EW, EK Sequence of Operation, Ð Air Quantity Limits

Table 17 Ð Air Quantity Limits

	MINIMUM HEATING	MINIMUM HEATING	MINIMUM COOLING
UNIT			AIRFLOW (VAV)	MINIMUM COOLING	MAXIMUM
	AIRFLOW	AIRFLOW
48EJ,EK,EW,EY			AT FULL LOAD	AIRFLOW (CV)	AIRFLOW
	(Low Heat)	(High Heat)
			OPERATION
024	5730	5950	2000	6,000	10,000
028	5730	5950	2500	7,500	12,500
030	5730	5950	2750	8,250	13,750
034	5730	5950	3000	9,000	15,000
038	7360	9820	3500	10,500	17,500
044	7360	9820	4000	12,000	20,000
048	7360	9820	4500	13,500	22,500

LEGEND

CV Ð Constant Volume

VAV Ð Variable Air Volume

Return-Air Filters Ð Check that correct ®lters are in- stalled in ®lter tracks (see Table 1). Do not operate unit with- out return-air ®lters.

Filter Replacement Ð To replace ®lters, open ®lter ac- cess door (marked with label). Remove inner access panel. Remove plastic ®lter retainer in between ®lter tracks by slid- ing and pulling outward. Remove ®rst ®lter by sliding it out of the opening in ®lter track. Locate ®lter removal tool, which is shipped next to the return air dampers. Use the ®lter re- moval tool to remove the rest of the ®lters.

Outdoor-Air Inlet Screens Ð Outdoor-air inlet screens must be in place before operating unit.

Economizer Adjustment Ð Remove ®lter access panel. Check that outdoor-air damper is closed and return-air damper is open.

Economizer operation and adjustment are described in Sequence of Operation section on this page; and Minimum Damper Position Setting section on page 24.

Gas Heat Ð Verify gas pressures before turning on heat as follows:

1.Turn off ®eld-supplied manual gas stop, located external to unit.

2.Connect pressure gage to supply gas tap, located on ®eld- supplied manual shutoff valve (see Fig. 13 on page 13).

3.Connect pressure gage to manifold pressure tap on unit gas valve.

4.Supply gas pressure must not exceed 13.5 in. wg. Check pressure at ®eld-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. On VAV units, the RAT (Return-Air Temperature) must be less than or equal to 68 F for heating to be energized. Use the ®eld test procedure to verify heat operation. After the unit 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 Operation

NOTE: Unit is shipped with default values that can be changed through Service Tool, Building Supervisor, or Comfort- Works™ software. See Table 18 for default values.

COOLING, CONSTANT VOLUME (CV) UNITS Ð On power up, the control module will activate the initialization software of the control board. The initialization software then- reads DIP switch no. 1 position to determine CV or VAV operation. Next, DIP switch no. 2 is read to determine if the control is thermostat or sensor type operation. If switch 2 is

open,then sensors are employed. If switch no. 2 is closed, thermostat is employed. Initialization clears all alarms and alerts, remaps the input/output database for CV operation, sets maximum heat stages to 2, and sets maximum cool stages to 3. The control reads DIP switch no. 3 and if open, then it sets the internal ¯ag for expansion mode operation.

The ®rst time power is sent to the control board after a power outage, power up takes 5 minutes plus a random 1 to 63 seconds.

The TSTAT function performs a thermostat based control by monitoring Y1, Y2, W1, W2, and G inputs. These func- tions control stages cool1, cool2, heat1, heat2, and indoor fan, respectively. If TSTAT function is NOT selected, the control 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 controlled as in the Occupied mode. User-de®ned set points are shown in Table 18.

The occupied or unoccupied comfort set points must be selected and the space temperature offset input will be used, if present. The Occupied Heat set point default value is 68 F. The Occupied Cool set point default value is 78 F. The Unoccupied Heat set point default value is 55 F. The Un- occupied Cool set point value is 90 F. The control board will set appropriate operating mode and fan control. The control board 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 against comfort set points and control heating or cooling stages as required. If system is in the Occupied mode, the economizer will operate as required. If the system is in Unoccupied mode, the system will perform nighttime free cool and IAQ (indoor air quality) pre-occupancy purge as required (when functions are enabled via software). Whenever the DX (di-rect expansion) cooling is requested, the outdoor fan will operate.

The control board will operate economizer, run diagnos- tics to monitor alarms/alerts at all times, and respond to CCN communications to perform any con®gured 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 expanded I/O points, perform Fire/Smoke control (power exhaust re- quired); and if in Occupied mode perform IAQ control and monitor fan, ®lter, demand limit, and ®eld-applied status (with accessories).

If thermostats are used to energize the G input, the control will turn on indoor fan without delay and open economizer dampers to minimum position.

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