Carrier JK034-074, 50FK, 48FK specifications VFD Set Point Frequency Command for Duct Pressure

Table 13 Ð VFD Set Point (Frequency Command) for Duct Pressure

PRESSURE	VFD SET POINT (Hz)	CONTROL SIGNAL	PRESSURE	VFD SET POINT	CONTROL SIGNAL
(in. wg)		(mA)	(in. wg)	(Hz)	(mA)
0.00	0	4.0	2.00	24	10.4
0.25	3	4.8	2.25	27	11.2
0.50	6	5.6	2.50	30	12.0
0.75	9	6.4	2.75	33	12.8
1.00	12	7.2	3.00	36	13.6
1.25	15	8.0	3.25	39	14.4
1.50	18	8.8	3.50	42	15.2
1.75	21	9.6

Table 14 Ð Changing the VFD Set Point (Frequency Command)*

KEY OPERATION	LED MESSAGE	EXPLANATION
	XX.X or OFF	Standard Monitor Mode (output frequency). If drive is disabled, display
		will read OFF . If enabled, display will show current output frequency
↓	60.0	Pressing arrow key once will display the current frequency setpoint
↓−	45.0 (¯ashing)	Pressing up/down arrow keys changes the desired setpoint
		When R/W is pressed, the parameter name (FC) and the new value
R/W	FC and 45.0 (¯ashing)	(45.0) will alternately ¯ash to indicate that the new value has been
		stored. After 2 cycles, the display will return to the standard monitor
		mode.
	XX.X or OFF	Standard Monitor Mode (output frequency). If drive is disabled, display
		will read OFF . If enabled, display will show current output frequency

*Choose set point from Table 13 according to desired duct pressure.

Modulating Power Exhaust (Option or Acces-

sory) Ð The Modulating Power Exhaust system will main- tain space pressure by modulating power exhaust fan no. 1 and staging power exhaust fan no. 2. Building pressure set point is established at the modulating power exhaust differ- ential pressure switch (DPS).

SIZE 034-048 UNITS Ð The modulating power exhaust dif- ferential pressure switch is located in the auxiliary control box mounted in the corner next to the power exhaust motor door. To gain access to this control box, remove the auxil- iary control box cover. When replacing cover, be sure to prop- erly secure it in order to prevent water from being drawn into the unit. See Fig. 33.

SIZE 054-104 UNITS Ð The modulating power exhaust dif- ferential pressure switch is mounted below the auxiliary con- trol box next to the access door labeled FILTER SECTION. See Fig. 35.

DIFFERENTIAL PRESSURE SWITCH Ð The modulating power exhaust DPS has a set point range of 0.5 in. wg to −0.5 in. wg. Factory setting is +0.1 in. wg. To adjust set point, turn set point adjusting screw (see Fig. 39) clockwise to decrease set point and counterclockwise to increase set point. This switch also has an adjustable null span. The null span is the pressure change that can be made without contacts opening or closing. It is adjustable from 0.06 in. wg to

0.14in. wg when set point is at minimum position (−0.5 in. wg) and 0.07 in. wg to 0.14 in. wg when set point is at maximum position (+0.5 in. wg). To adjust null span, turn null adjusting screw (Fig. 39) clockwise to decrease span and counterclockwise to increase span. All switches leave factory with null span set at maximum position. The smaller the null span, the closer the pressure will be maintained to desired set point.

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