Variable Frequency Drive

Economizer Motor Ð All control of the motor (i.e., enthalpy changeover, minimum position control and mixed air control) is accomplished from the main unit microproces- sor through a relay board. Service and installation instruc- tions for the unit should be consulted to verify proper op- eration of these controls. The economizer motor may be checked out separately. See Fig. 52 for VAV economizer motor con- nection information.

Motor Test

Apply 24 volt AC power to terminals T1 and T2 of motor. Connections to motor terminals 2 and 3 must be disconnected

A Motor Test	A Expected Result and Response
Jumper 1 to	Motor drives open; if not,
2 at motor	replace motor.
B Motor Test	B Expected Result and Response
Jumper 1 to	Motor drives closed; if not,
3 at motor	replace motor.

LIMIT SWITCHES
CAPACITOR
		3
CW			ECONOMIZER
WINDING		2	ECONOMIZER
(OPEN)			MOTOR
CCW
WINDING		T1
(CLOSE)		T1
(CLOSE)
1		T2
1	BRAKE		1
	BRAKE		1
	WINDING
CW		1
CW
		2
FEEDBACK
POTENTIOMETER
		3
			BLU
			RED
			YEL

AUX. SWITCH

LEGEND

CCW Ð Counterclockwise

CW Ð Clockwise

Fig. 52 Ð Damper Motor Connection Diagram (VAV)

Factory-installed optional VFD is located near the sup- ply fan and motor. During any service work or pro- gramming at the VFD, operation of the fan and motor is not desirable. Either disable the supply fan or install an accessory VFD remote display.

NOTE: The VFDs (part no. TOSVERT130-E3) are specially modi®ed for use on Carrier equipment. Some speci®cations and control con®guration defaults for Carrier applications will differ from the VFD manufacturer manual included in the packet. See Table 29 for listing of Carrier-speci®c de- fault values.

STANDARD TRANSDUCER CONTROL Ð The VFD moni- tors and controls duct pressure (DP) via a differential pres- sure transducer. The pressure transducer is located in the auxiliary control box (034-048 units) or in the supply fan compartment (see Fig. 34). The pressure transducer's low pressure reference port is connected to the outside of the unit cabinet by a factory-installed tubing section. The pressure transducer's high pressure reference point must be ®eld- connected to the duct pressure pick-up (®eld-supplied and installed in the supply duct).

The DP transducer monitors the static pressure in the sup- ply duct and provides a 4 to 20 mA signal directly to the VFD. (Refer to Table 13 for transducer output signal (mA) for actual duct static pressure.) The internal logic of the VFD compares this signal representing actual duct pressure to the user-con®gured DP set point. The VFD automatically ad- justs its output to the supply fan motor to maintain the de- sired DP set point. When operating with the factory-standard DP transducer, the internal PID logic of the VFD is enabled.

EXTERNAL SIGNAL CONTROL Ð If the VFD is to be controlled by an external control system other than the fac- tory supplied pressure transducer, the internal PID logic func- tion of the VFD must be disabled. To disable the PID control:

1.Disconnect all power to the unit and the VFD.

2.Install a jumper across S2-CC (see Fig. 53 and 54 for VFD terminal board connections).

3.Remove factory-supplied cable attached to IV and CC.

4.Remove other end of the same cable from the pressure sensor.

5.Connect ®eld supplied speed reference (4 to 20mA) across terminals IV-CC.

6.Disable the supply fan motor operation.

7.Reconnect power to the unit and VFD.

8.Reprogram the VFD to accept an external reference (in the Utility parameters group [Gr.Ut], set parameter item Fnod [no.312] = 4).

9.Enable supply fan motor and return power to the unit.

SUPPLY FAN MOTOR OVERLOAD PROTECTION Ð The VFD provides operating overload protection for the supply fan motor. The factory has programmed the VFD overload function to match the factory-installed motor (motor size and efficiency). If the supply fan motor is changed from the origi- nal factory selection, the overload value may need to be changed by the service person. Contact your local Carrier represen- tative for assistance in determining the proper overload setting.

NOTE: Variable frequency drive size is matched to factory- installed motor size. Do not increase motor size without also changing to equivalent VFD size.