Carrier 48MPD, MPE62L-10R Controls Conguration and Quick Test, Ð Component Pressure Drop in. wg

Table 18 Ð Component Pressure Drop (in. wg)

COMPONENT	22,000	26,400	30,000	34,000	38,000	42,000	45,800	48,200	52,000
HEAT EXCHANGER	0.31	0.40	0.49	0.58	0.70	0.82	0.95	1.03	1.23
(48MP ONLY)

Table 19 Ð Maximum Allowable

Supply Fan Wheel Speed (Rpm)

48/50MP	FAN TYPE
	Forward Curved	Airfoil
62L, 70M	835	1595
82N, 90P, 10R	715	1298

Table 20 Ð Maximum Allowable Power Exhaust

Fan Speed (Rpm)

48/50MP		FAN TYPE
	50% Air		100% Air
62L, 70M	690		650
82N, 90P, 10R	600		560

Table 21 Ð Air Quantity Limits (cfm)

			MINIMUM	MINIMUM
UNIT			GAS HEATING	GAS HEATING
SIZE	MINIMUM	MAXIMUM	(Low Heat	(High Heat
48/50MP			Units)	Units)
			48MPD	48MPE
62L	16,000	32,000	12,850	15,400
70M	18,000	36,000	12,850	15,400
82N	21,000	42,000	14,700	19,250
90P	23,000	46,000	14,700	19,250
10R	26,000	52,000	14,700	19,250

Controls Con®guration and Quick Test

SUPPLY FAN STATUS SWITCH (FS) Ð A snap acting single- pole, double-throw (SPDT) differential pressure switch is fac- tory mounted in the auxiliary control box. The switch senses the change in pressure across the supply-air fan and pro- vides the fan status. A length of plenum tubing connects the switch to the probe located in the fan discharge box.

The switch must be set prior to unit operation. To set the switch, turn the adjustment screw on top (center) of switch clockwise to increase set point, or counterclockwise to decrease set point. The set point switch range is 0.05 to

2.0in. wg with a deadband of 0.02 in. wg at minimum set point and 0.1 in. wg at maximum set point.

Set switch so that contact makes to NC when supply-air fan is energized. The switch should make (fan on) within 1 minute after supply-air fan is energized and break (fan off) within 1 minute after the fan is deenergized.

CHECK FILTER SWITCH (CFS) Ð A snap acting SPDT switch is factory mounted in the auxiliary control box. The switch senses the differential pressure and provides the micro- processor module with a signal for ®lter status. Two lengths of plenum tubing connect the switch to probes located both upstream and downstream of the unit ®lters.

The switch must be set prior to unit operation. To set the switch, turn the adjustment screw on top (center) of switch slowly clockwise to ®nd the ``pivot'' point where the ®lter

status still reads clean under in the HSIO display. Check the switch operation with the supply-air fan running

and nominal cfm delivery. See Table 22 for clean ®lter pres- sure drops for help in locating the ``pivot'' point. Once this point is found, turn the screw clockwise to obtain the set point at which the ®lter status will be dirty. Use Table 22 as a guide.

Table 22 Ð Filter Switch Dirty Set Point

	INCREASED
	PRESSURE DROP	APPROXIMATE
FILTER TYPE	TO ``DIRTY''	CLOCKWISE
	FROM PIVOT	TURNS
	POINT
2-in. Throwaway	0.30 in. wg	2
4-in. Pleated with	0.75 in. wg	5
2-in. Throwaway

ENTHALPY CONTROL SET POINT Ð The enthalpy sen- sor (See Fig. 45) is located behind the ®lters in the right side economizer hood and is accessed through the ®lter access door. For maximum bene®t of outdoor air, set enthalpy sen- sor control to the A setting. At this setting, when the relative humidity is 50%, and the outdoor air is below 74 F, the sen- sor's relay contacts will be closed. See Fig. 46 and 47.

NOTE: Enthalpy control setting dial is on the enthalpy control.

Economizer Damper Linkage Adjustment Ð When replac- ing economizer damper motors, or if the linkage has come loose, it is critical that the linkages be adjusted correctly. They are sensitive, and incorrect adjustment can cause the motor to stall. Check linkage for free movement and com- plete range of travel.

Minimum Position Set Point Ð Minimum economizer po- sition is set using the keypad and display module. Refer to Control and Troubleshooting literature for more details.

ENTHALPY

SENSOR

Fig. 45 Ð Enthalpy Sensor

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