Carrier 48HJ015-025 Base Unit Operation, Accessory/FIOP Economizer Static Pressure in. wg

Table 7 Ð Accessory/FIOP Economizer Static Pressure (in. wg)

UNIT	UNIT	CFM	ECONOMIZER
480HJ	VOLTAGE		PRESSURE DROP
		3,750	.03
015, 017		4,000	.03
	All	5,000	.05
		6,000	.07
		7,500	.10
		6,000	.07
025	All	7,200	.09
		9,000	.11
		10,000	.12

LEGEND

BHP Ð Brake Horsepower

FIOP Ð Factory-Installed Option

NOTES:

1.The factory-assembled horizontal adapter substantially improves fan performance. See Fig. 24.

2.The static pressure must be added to external static pressure. The sum and the evaporator entering-air cfm should then be used in conjunction with the Fan Performance table to determine blower rpm, bhp, and watts.

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

1.Turn off manual gas stop.

2.Connect pressure gage to supply gas tap (See Fig. 13 on page 8).

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

4.Turn on manual gas stop and set thermostat to HEAT po- sition. After the unit has run for several minutes, verify that incoming pressure is 5.0 in. wg or greater, and that the manifold pressure is 3.5 in. wg. If manifold pressure must be adjusted, refer to Gas Valve Adjustment section on page 22.

5.After unit has been in operation for 5 minutes, check tem- perature rise across the heat exchangers. See unit infor- mative plate for correct rise limits of the heat supplied. Air quantities may need to be adjusted to bring the actual rise to within the allowable limits.

Base Unit Operation

COOLING, UNITS WITHOUT ECONOMIZER Ð When thermostat calls for cooling, terminals G and Y1 are ener- gized. The indoor (evaporator) fan contactor (IFC) and compressor contactor no. 1 (C1) are energized and evaporator- fan motor (IFM), compressor no. 1 (017,025) or unloaded compressor (015), and condenser fan start. The condenser- fan motors run continuously while unit is cooling. If the ther- mostat calls for a second stage of cooling by energizing Y2, compressor contactor no. 2 (C2) is energized and compres- sor no. 2 starts (017,025), or compressor no. 1 runs fully loaded (015).

A freeze protection thermostat (FPT) is located on the evaporator coil. It detects frost build-up and locks out the compressors, allowing the coil to clear. Once frost has melted, the compressors can be reenergized by resetting the thermostat.

HEATING, UNITS WITHOUT ECONOMIZER

NOTE: The 48HJD015 units have 1 stage of heat, and the 48HJE015, 48HJE017, and HJD025 units have 2 stages of heat.

First Stage Ð Turn unit power on. Open manual gas line valve. Set thermostat system switch at HEAT or AUTO. po- sition and set fan switch to AUTO. position for heating.

First-stage thermostat calls for heat. Time-delay relay for evaporator fan begins timer sequence. Induced-draft relay closes, and induced-draft motor starts.

Pressure switch closes and pilot valve no. 1 opens, allow- ing gas to ¯ow to the ®rst-stage pilot. Spark ignitor ignites pilot ¯ame. Sensor detects ¯ame and the main gas valve no. 1 opens. Gas ¯ows to main burners and ®rst-stage burners ignite. Spark igniter turns off.

When sequence is complete, time-delay relay closes and evaporator fans start.

Second-Stage Ð On 2-stage units, with an additional heat- ing call, the second-stage thermostat closes. (The control re- lay [HR2] closes during the ®rst stage of operation.) Pilot valve no. 2 opens, and the spark ignitor ignites pilot. The sensor detects a ¯ame and energizes main gas valve coil no. 2, opening main gas valve no. 2. Gas ¯ows to the main burners, and the second-stage burners ignite. The spark ignitor turns off.

When the second-stage thermostat is satis®ed, the second- stage gas valve closes.

When the ®rst-stage thermostat is satis®ed, the ®rst-stage gas valve closes. The induced-draft motor turns off, the time delay relay is deenergized, and the timer sequence begins. When the sequence is complete, the evaporator-fan motor turns off.

COOLING, UNITS WITH ECONOMIZER Ð Upon a call for cooling, when outdoor ambient is above the changeover control setting, the economizer damper moves to VENT position. The compressors and evaporator and condenser fans energize and operate as per Cooling, Units Without Econo- mizer section above.

Upon a ®rst call for cooling, when outdoor ambient is be- low the changeover control setting, the evaporator fan starts and the economizer is fully open. The compressors remain off.

Upon a second-stage call for cooling, compressor no. 1 (017,025) or unloaded compressor (015) is energized and me- chanical cooling is integrated with economizer cooling. If the outdoor-air temperature drops below 50 F, a cooling lock- out switch prevents the compressors from running.

When supply-air temperature drops below a ®xed set point, the economizer damper modulates to maintain the tempera- ture at the ®xed set point.

HEATING, UNITS WITH ECONOMIZER Ð Outdoor-air damper stays at VENT position while evaporator fan is operating.

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