Carrier JK034-074, 50FK, 48FK specifications Integrated Circuit, Input

LEGEND

ECON Ð Economizer

MIN Ð Minimum

PÐ Potentiometer

VAV Ð Variable-Air Volume

Fig. 15 Ð Accessory Relay Board

(Standard; Factory Supplied)

		LEGEND
IC	Ð	Integrated Circuit
IN	Ð	Input

PÐ Potentiometer RTN Ð Return

Fig. 16 Ð Two-Step Demand Limit Module

Fig. 17 Ð Enthalpy Sensor Location

Variable Frequency Drive (VFD) Ð The optional VFD is used to modulate supply fan air¯ow to maintain duct static pressure on VAV applications. The VFD is located in the supply fan section (see Fig. 18 and 19), and can be ac- cessed by opening the fan section access door.

The unit is supplied with a pressure transducer capable of measuring from 0.0 to 5.0 in. wg. The pressure transducer will send a 4 to 20 mA signal to the VFD to modulate the speed of the indoor fan motor to precisely control the fan to the desired static pressure set point. The VFD is factory set at 2.5 in. wg duct static pressure. Refer to the Operating Se- quence section for more information on the VFD.

The VFD has been programmed and wired at the factory for this application. No further adjustments (except for Duct Static Pressure Set Point) should be necessary at start-up. Factory jumper wire con®gurations are shown in the Supply Fan Control with VFD Option section on page 28.

A separate service manual for the factory-installed VFD is supplied with each unit. Refer to the VFD manual for more information on the VFD controls.

Temperature Reset Ð Accessory temperature reset al- lows the unit to automatically adjust (``reset'') the supply- air temperature set point to a higher value once most of the space cooling load has been met. When the space conditions are satis®ed, the VAV terminals will close to the minimum position. All VAV units will sense the decrease in actual supply- air temperature and the unit controls respond by reducing

Fig. 18 Ð Variable Frequency Drive,

Sizes 034-048 and 078-104

Fig. 19 Ð Variable Frequency Drive, Sizes 054-074

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