Carrier 48EJ, EW, EK, EY024-048 VFD Supply Air Pressure Set Point, Pressure Control VFD, SET Point

To set the VFD, the VFD must be powered up; however, since it is located near the indoor air fan, operation of the fan is not desirable. To disable the fan, perform the follow- ing procedure:

1.Open the indoor fan circuit breaker.

2.Remove the jumper between CC and ST on the terminal strip of the VFD (see Fig. 41).

3.Close the indoor fan circuit breaker. The VFD now is powered but the fan will not operate.

4.On the front of the VFD is a keypad and display which will be used to enter the set point. To access this ®eld, press the ``PRG'' key until the display reads ``S.PrG'' (Speed Group Parameters). Press the arrow key until ``Sr1'' is displayed. This is the VFD set point listed in Table 7.

5.Press the ``READ/WRITE'' key. The set point value will be displayed. Use the up-arrow or down-arrow key to adjust the set point value to the value desired.

6.Press the ``READ/WRITE'' key again to enter the new value.

7.Check the factory default values.

IMPORTANT: The Carrier factory default values for the VFD may be different than the default val- ues of the manufacturer. Refer to the Carrier lit- erature when checking default values. The following default values have been changed from the manu- facturer settings to more closely match the VFD operation to a Carrier VAV unit.

SETUP PARAMETERS (Item 6, Point 1, Output Fre- quency) Ð The default value should be 20.

JUMP FREQUENCY GROUP (Item 7, PID Set Point Control Select) Ð The default value is 1.

JUMP FREQUENCY GROUP (Item 8, Proportional Gain) Ð The default value is 100.

JUMP FREQUENCY GROUP (Item 9, Integral Gain) Ð The default value is 50.

SPEED GROUP PARAMETERS (Item 2, Multi-Speed Run Frequency No. 1) Ð The factory setting is 30.

SPEED GROUP PARAMETERS (Item 2, Fire Speed Override Frequency) Ð The factory setting is 60.

8.Open the indoor fan circuit breaker.

9.Replace the jumper between CC and ST on the terminal strip of the VFD.

10.Close the indoor fan circuit breaker; the VFD now is powered and the fan will operate.

NOTE: Any ®eld measurement of supply fan amps must be taken with an RMS meter between the fan circuit breaker and fan contactor (upstream of VFD).

Power Exhaust Ð The optional non-modulating power exhaust (CV only) is a two-stage design where the operation of the exhaust fans is linked to economizer position. When the supply fan is running and the economizer is 25% open,

the base module closes contacts, activating two exhaust fans. When the economizer position reaches 75% open, the base module activates the other two exhaust fans. The fans will turn off when the economizer closes below the same points. The economizer position set points that trigger the exhaust fans can be modi®ed, but only through use of the Service Tool, Comfort Works, or Building Supervisor software. If single-stage operation is desired, adjust the economizer set points to identical values at the desired point to activate all exhaust fans.

The optional modulating power exhaust (VAV standard, CV optional) is controlled by a modular electronic se- quencer system. This system consists of a model R353 sig- nal input module and 4 model S353 staging modules. The signal input module receives a 0 to 10 vdc signal from the building pressure transducer, which is mounted adjacent to the supply static transducer behind the ®lter access panel. The modules are mounted just below the unit control board. The left module is the R353, and the 4 modules on the right are S353 modules for stages 1 through 4. On the unit wiring label, the R353 is designated PESC, and the S353 modules are designated PES1 through PES4.

The building pressure transducer range is −0.5 to

+0.5 in. wg. It is powered by a 0 to 10 vdc signal. A factory- installed hose at the ``Lo'' connection leads to atmosphere, and a ®eld-supplied hose must be connected to the ``Hi'' con- nection and led into the building to a point where building pressure is to be controlled (positive-pressure building). There is a plug button in the bulkhead just above the transducers, for use in leading the hoses into the building via the return air ductwork.

There are 3 adjustments at the R353 module, all of which have been factory set. In the center of the circuit board is a set of 4 pins with a jumper, labeled J2. This determines the mode of operation. The bottom two pins must be jumpered for direct operation. Direct operation means that the stag- ing modules are activated in sequence as the input signal increases.

Table 7 Ð VFD Supply Air Pressure Set Point

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

VFD Ð Variable Frequency Drive

FLA FLB FLC P24 RCH LOW FM

AM

PP

RR

IV

CC

ST

F

R

(SS2) (SS3)

CC SS1 JOG AD2 RST CC

+

–

NOTE: Terminal strip is located inside the VFD at the bottom. D P D P JUMPERS

Fig. 41 Ð VFD Factory-Installed Jumpers

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