Carrier PC 111 User Manual

Controls Operation,

and Troubleshooting

CONTENTS

Page

SAFETY CONSIDERATIONS GENERAL

Rooftop Information VAV Control System Processor Board

• P1 — SUPPLY-AIR SET POINT

• P2 — ECONOMIZER POSITION

• P3 — RESET LIMIT

• P4 — DEMAND LIMIT

• P5 — ECONOMIZER MINIMUM POSITION

• P6 — WARM-UP SET POINT

• P7 — SASP RESET TEMPERATURE

• PROCESSOR BOARD OUTPUTS

• CONFIGURATION HEADER AND DIP SWITCH ASSEMBLY

Relay Board Display Board Thermistors

• T1 — SUPPLY-AIR TEMPERATURE THERMISTOR

• T2 — RETURN-AIR TEMPERATURE THERMISTOR

• T3 — SA TURATED CONDENSING TEMPERATURE, CIRCUIT 1

• T4 — SA TURATED CONDENSING TEMPERATURE, CIRCUIT 2

• T10 — RESET TEMPERATURE

Compressor Operation

• CONTROL RELAY (CR)

Accessory Board

• P3 — RESET LIMIT

• P5 — ECONOMIZER MINIMUM POSITION

• P6 — MORNING WARM-UP TEMPERATURE

Single-Step Demand Unit Demand Limit Control Module (DLCM) Economizer

• ENTHALPY CONTROL

• DIFFERENTIAL ENTHALPY

Supply Fan Variable Frequency Drive (VFD) High Capacity Modulating Power

Exhaust Variable Frequency Drive

Temperature Reset CONTROLS INSTALLATION

Control Wiring

• NIGHT SETBACK THERMOSTAT

• SPACE TEMPERATURE RESET ACCESSORY (50DJ900021)

Space Temperature Reset

• INSTALLATION

• CONFIGURATION

• OPERATING SEQUENCE

Demand Limit

• SINGLE-STEP DEMAND LIMIT

• TWO-STEP DEMAND LIMIT

• INSTALLATION

• CONFIGURATION

• OPERATING SEQUENCE

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

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. . . . . . . . . . . . . . . . . . 13-25

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48FK,JK034-104

48FM078-104

50FK,FY,JK,JY034-104

50FM,FS078-104

Variable-Air Volume Rooftop Units

Page

Control From Remote Building Management

System (BMS)

• OCCUPIED/UNOCCUPIED

• NIGHT SETBACK CONTROL

• UNIT SUPPLY AIR SET POINT ADJUSTMENT

• DEMAND UNIT (1-STAGE OR 2-STAGE)

• SUPPL Y DUCT PR ESSURE SET PO INT ADJUS TMENT

• EXTERNAL ALARM SIGNAL

• REMOTE ECONOMIZER CONTROL

Smoke Control Modes

• FIRE SHUTDOWN MODE

• PRESSURIZATION MODE

• EVACUATION MODE

• SMOKE PURGE MODE

• INSTALLATION

• CONFIGURATION

• OPERATI NG SEQUENCE

Air Pressure Tubing

• INLET GUIDE VANES

• SUPPLY FAN VARIABLE FREQUENCY DRIVE

• MODULATING POWER EXHAUST

START-UP Initial Check Configuration Header DIP Switches Adjusting Set Points Potentiometers Supply Fan Control with IGV Option Supply Fan Control with VFD Option Modulating Power Exhaust Option or

Accessory) (48FK,JK and 50FK,JK Units)

High Capacity Power Exhaust

(48FM and 50FM,FS Units)

START UNIT Quick Test Program

OPERATING INFORMATION Digital Display

• CODES 0 THROUGH 8, CAPACITY STEPS

• CODES 20 THROUGH 30 AND 88, OPERATIONAL STATUS

• CODES 51 THROUGH 87, DIAGNOSTIC INFORMATION

Operating Sequence

• SIZE 034, 038 AND 048-088 UNITS

• SI ZE 044 UNITS

• SI ZE 104 UNITS

Head Pressure Control Supply Fan Control with IGV Supply Fan Control with VFD Modulating Power Exhaust (48FK,JK and

50FK,JK Units Option or Accessory)

High Capacity Modulating Power Exhaust

(48FM and 50FM,FS Units)

Unit Staging

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

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Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

Book 1 1 Tab 1a 1b

PC 111 Catalog No. 534-763 Printed in U.S.A. Form 48/50F,J-3T Pg 1 3-00 Replaces: 48/50F,J-1T

CONTENTS (cont)

Page

TROUBLESHOOTING Checking Display Codes Complete Unit Stoppage Single Circuit Stoppage Restart Procedure Diagnostic Codes

• CODES 51, 52, 55, 56: COMPRESSOR FAILURE

• CODES 59 AND 60: LOW-PRESSURE SWITCH

• CODES 63 AND 64: OIL PRESSURE SWITCH

• CODE 70: ILLEGAL UNIT CONFIGURATION

• CODES 71 TO 76: THERMISTOR/RESISTOR FAILURE

• CODE 81: RESET THERMISTOR OR POTENTIOMETER FAILURE

• CODE 82: SUPPL Y-AIR TEMPER ATURE SET POINT POTENTIOMETER FAILURE

• CODE 83: ECONOMIZER FEEDBACK POTENTIOMETER FAILURE

• CODE 84: RESET LIMIT POTENTIOMETER FAILURE

• CODE 85: DEMAND LIMIT POTENTIOMETER (P4) FAILURE

• CODE 86: MINIMUM POSITION ECONOMIZER POTENTIOMETER FAILURE

• CODE 87: WARM-UP TEMPERATURE SET POINT FAILURE

Thermistor Troubleshooting Electronic Controls Checkout

• PROCESSOR BOARD CHECKOUT

• RELAY BOARD TROUBLESHOOTING

• DISPLAY BOARD CHECKOUT

• ACCESSORY BOARD CHECKOUT

• TWO-STEP DEMAND LIMIT CONTROL MODULE (DLCM) TROUBLESHOOTING

Enthalpy Sensor Checkout Economizer Motor Supply Fan Variable Frequency Drive

• STANDARD TRANSDUCER CONTROL

• EXTERNAL SIGNAL CONTROL

• SUPPLY FAN MOTOR OVERLOAD PROTECTION

•VFD OPERATION

• VFD OPERATIONAL STATUS

• RESTORING FACTORY VFD DEFAULTS

Power Exhaust Variable Frequency Drive

• STANDARD TRANSDUCER CONTROL

• EXTERNAL SIGNAL CONTROL

• POWER EXHAUST FAN MOTOR NO. 1 OVERLOAD PROTECTION

• POWER EXHAUST VFD OPERATION

• POWER EXHAUST VFD OPERATIONAL STATUS

• RESTORING FACTORY POWER EXHUAST VFD DEFAULTS

Unit Wiring START-UP CHECKLIST

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

. . . . . . . . . . . . . . . . . . . . . . . . . 44-60

. . . . . . . . . . . . . . . . . . . . . . . . 44

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. . . . . . . . . . . . . . . . . . . . . 48

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. . . . . . . . . . . . . . . . . . . . . . 52

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. . . . . . . . . . . 52

. . . . . . . 55

. . . . . . . . . . . . . . . . . . CL-1, CL-2

SAFETY CONSIDERATIONS

Installing, starting up, and servicing this equipment can be

hazardous due to system pressures, electrical components, and equipment location (roof, elevated structures, etc.). Only trained, qualified installers and service mechanics should install, start up, and service this equipment.

When working on this equipment, observe precautions in

the literature; on tags, stickers, and labels attached to the equipment, and any other safety precautions that apply. Follow all safety codes. Wear safety glasses and work gloves. Use care in

handling, rigging, and setting this equipment, and in handling all electrical components.

Electrical shock can cause personal injury and death. Shut off all power to this equipment during installation and service. There may be more than one disconnect switch. Tag all disconnect locations to alert others not to restore power until work is comp lete d.

This unit uses a microprocessor-based electronic control system. Do not use jumpers or other tools to short out components, or to bypass or otherwise depart from recommended procedures. Any short-to-ground of the control board or accompanying wiring may destroy the electronic modules or electrical components.

GENERAL

IMPORTANT: This literature contains controls, operation, and troubleshooting data for 48FK,FM,JK and 50FK,FM,FS,FY,JK,JY variable air volume rooftop units. Use this guide in conjunction with the separate Installation Instructions literature packaged with the unit.

Carrier 48FK,FM,JK and 50FK,FM,FS,FY,JK,JY units provide ventilation, cooling, and heating (when equipped) in Variable Air Volume (V AV) applications. These units contain factory-installed controls which provide full system management. The unit controls also perform self diagnostic tests at unit startup, monitor operation of the unit, and provide alarms. Information on system operation and status are sent to the central processors by various sensors that are located at the unit and in the conditioned space. Each unit is equipped with a display board.

Rooftop Information —

supply-fan motor, compressors, and unloaders to maintain the proper temperature conditions. The controls also cycle condenser fans to maintain suitable head pressure. Safeties are continuously monitored to prevent the unit from operating under abnormal conditions. The controls provide control of economizer and cycle or control heating as required.

The controls also allow the service person to operate a ‘quick test’ so that all the controlled components can be checked for proper operation.

IMPORTANT: The field-supplied and installed switch

(or timeclock) MUST BE CLOSED to put unit into the

Occupied mode. Unit WILL NOT START until this is

accomplished. See base unit installation instructions lit-

erature for details.

VAV Control System —

top units contain a microprocessor-based electronic control system that controls and monitors the rooftop unit functions.

The VA V control system is composed of several components:

• processor board

• relay board

• display board

• thermistors

• compressor operation feedback (control relay)

• accessory board

• temperature reset package*

• single-step demand limit*

• two-step demand limit control module* *Field-insta lled acc esso ries.

The rooftop controls cycle

The 30 to 100-ton VAV roof-

The VAV control system monitors and controls the follow-

ing functions of the rooftop unit:

• supply-air temperature (unit capacity)

• morning warm-up or electric heat (if equipped)

• head pressure control, fan cycling

• economizer position

• diagnostic display

• unit check-out (quick test)

• supply air temperature reset (if equipped)

• demand limiting (if equipped)

Processor Board —

The processor board, shown in Fig. 1, contains the logic and the necessary hardware to drive the outputs and the display board. The processor board is enclosed by a sheet metal cover and a heater. The heater is controlled by a thermostat to keep the processor temperature above 32 F (0° C). All electrical connections are made t o the proc essor board through wire and ribbon cables.

Several temperature inputs are connected to the processor. There are either 4 or 5 thermistors (depending on the fieldinstalled accessories) which input temperature data into the processor through pin terminal connector J1. See Table 1 and Fig. 2.

Several status switches are also monitored. These switches are connected to the processor at pin terminal connector J2. See Fig. 3 and T able 2.

In addition to the unit status switch inputs, the processor board also accepts inputs from several potentiometers. These potentiometers control various operational characteristics of the system. Inputs are received by the processor through pin terminal connector J3. See Fig. 4.

Table 1 — Pin Terminal Connector J1

Thermistor Inputs

CONNECTOR J1

TERMINAL NO.

1,2

14,15

16,17

18,19 20,21

LEGEND

Thermistor

T —

*If equipped with accessory temperature reset package. NOTE: Terminal numbers 3-13 are not used on these units.

TEMPERATURE

INPUT

Reset Temperature* T10 Saturated Condensing

Temp., Circuit 2 Saturated Condensing

Temp., Circuit 1 Return-Air Temperature T2 Supply-Air Temperature T1

UNIT SIZE

034-104

LEGEND

DIP — EPPOM — EXV —

Do not remove label covering EPROM. Removal causes program to be erased.

Dual In-Line Package Erasable, Programmable Read-Only Memory Electronic Expansion Valve

Fig. 1 — Processor Board

*EPROM HT204485-1-XX where “XX” is the current revision

number. NOTE: Processor Board is positioned in unit with J3 and J10 connections at the bottom.

LEGEND

T—

Thermistor Field Wiring Accessory

Fig. 2 — Pin Terminal Connector J1

Thermistor Inputs

LEGEND

CR — EC — LPS —

Control Relay Enthalpy Control Low-Pressure Switch

Fig. 3 — Pin Terminal Connector J2

Status Switch Inputs

Table 2 — Pin Terminal Connector J2

Status Switch Inputs

CONNECTOR J2

TERMINAL NO.

1,2

3,4

7,8

9,10

13,14

15,20

15,24

LEGEND

CR — EC — LPS —

NOTE: Terminal numbers 5, 6, 11, 12, 16-19, and 21-23 are not used on these units.

Control Relay Enthalpy Control Low-Pressure Switch

STATUS SWITCH

Oil Pressure, Circuit 2

Oil Pressure, Circuit 1

Loss of Charge, Circuit 2

Loss of Charge, Circuit 1

Economizer Changeover

Compressor Fault Signal

UNIT SIZE

034-104

Jumpered

LPS2

LPS1

CR2

CR1

LEGEND

IN — P— RNT — SW —

Input Factory Wiring Potentiometer Field Wiring Return Accessory Switch

Fig. 4 — Pin Terminal Connector J3

Potentiometer Inputs

All of the potentiometers must be set before the unit is started in order for the unit to function prope rly. See Start Up, Potentiometers section on page 27 for information on establishing set points. Each of the potentiometers has a valid range that is used by the control. The valid range is defined as the potentiometer’s resistance value that the control will not consider to be in error. This is usually between 10% and 90% of the potentiometer’s total resistance. The control has be en programmed to accept an operational range for the potentiometer, which may not be the same as the valid range.

The potentiometer locations and functions are as follows: P1 — SUPPLY-AIR SET POINT — This potentiometer is

located on the display board. The supply-air set point is the cooling mode control temperature which the VAV control system will attempt to maintain at Thermistor T1 by control of economizer position and/or cycling unloaders and compressors.

P2 — ECONOMIZER POSITION — Economiz er feedback potentiometer is located on the economizer motor. The microprocessor is programmed to indicate an alarm if the travel during initializatio n is less than 10% of the tota l potentiometer ’s resistance. An alarm condition will also be signaled if the potentiometer fails during operation, indicating that the damper blades are stuck. If either situation occurs, the processor will try to drive the economizer dampers closed.

P3 — RESET LIMIT — This potentiomet er is located on the accessory board (provided standard from the factory) in the unit main control box and establishes the maximum amount of reset that can be applied to the supply-air set point (P1). Reset is limited by the P1 default of 70 F. This potentiometer is used only when accessory, field-installed temperature reset is used. If temperature reset is used, DIP (dual, in-line package) switch 2 must be in the ON position.

P4 — DEMAND LIMIT — This potentiometer is located near TRAN4 in the unit control box. The demand limit potentiometer is used only if accessory, field-installed demand limit is used, and if DIP switch 5 is in the ON position. For single-step demand limit, a field-installed 5 to 20 Kohm potentiometer and switch must be used.

P5 — ECONOMIZER MINIMUM POSITION — This potentiometer is on the accessory board (provided standard from the factory) located in the unit main control box. This potentiometer specifies the minimum opening position for the optional economizer. If a fault condition is detected by the processor, an alarm condition will be signaled and the economizer dampers will close.

P6 — WARM-UP SET POINT — This potentiometer is on the accessory board (provided standard from the factory) located in the unit main control box. This potentiometer establishes the set point temperature for the Morning Warm-Up function. When the temperature is reached, Morning Wa rm-Up is terminated and VAV operation begins. DIP switch 4 must be in the ON position if morning warm-up heat is to be used.

P7 — SASP (SUPPLY AIR SET POINT) RESET TEMPERATURE — This 10 Kohm potentiometer is used only if the accessory, field-installed temperature reset package is installed. This potentiometer determines the temperature at w hich reset will begin. It is located on the accessory temperature reset board. DIP switch 2 must be in the ON position to enable SASP reset.

PROCESSOR BOARD OUTPUTS — The processor board also controls outputs through the relay board. The relay board plugs into the processor board using a ribbon cable.

In addition, the processor board controls the display board. The display board is connected to the processor board by a ribbon cable, and has an LED (light-emitting diode) display showing the status of the unit and diagnostic information.

CONFIGURATION HEADER AND DIP SWITCH ASSEMBLY — The processor board is programmed to control a variety of air conditioning units. To tailor the processor to the particular unit being controlled, 2 devices are used. One is the configuration header, and the other is the DIP switch assembly.

The configuration header (part no. 30GB660001) is a series of 8 small wires that are broken or unbroken in a pattern to indicate several unique characteristics of the unit. The configuration header is factory set and should not be changed. Changing the factory setting may cause the unit to malfunction.

The DIP switches configure the unit for several field-installed options, as well as for several other options that may be unique to the unit. The DIP switches are located under a plastic enclosure which must be removed for access. The switches can be field adjusted, but must be adjusted only when the unit control circuit breaker is off.

Relay Board —

and 115-v loads. See Fig. 5. The relay board is connected to the processor board by a ribbon cable at pin J9. Electrical conne ctions to the relay board are made through pins J5 (115 v) and J6 (24 v). The relay board has eight 24-v relays and five 115-v relays. See Table 3.

Display Board —

main unit control box and is connected to the J10 port of the processor board through a ribbon cable. The display board contains the supply-air set point potentiometer P1; a 2-digit, LED display; and the display button (see Fig. 6). The LED display is used to convey the operating information and operational error codes.

Thermistors —

sense the temperatures at various points in the system. See Table 1 and Fig. 7-14. All the thermistors have identical temperature versus resistance and voltage drop characteristics, and are monitored by the processor for a short or open circuit. The valid range for a thermistor is 362,640 to 219 ohms. Thermistor details and locations are as follows:

T1 — SUPPLY-AIR TEMPERATURE THERMISTOR — This thermistor is located in the unit supply fan discharge. It provides information for the processor to stage the number of capacity steps required to maintain a desired supply-air te mperature.

T2 — RETURN-AIR TEMPERATURE THERMISTOR — This thermistor is located in the mixed-air portion of the unit cabinet. The thermistor ’s primary function is to provide morning warm-up information. This sensor will also provide differential information for the processor during cooling operation (such as the rate of change for a capacity step).

T3 — SATURATED CONDENSING TEMPERATURE, CIRCUIT 1 — This thermistor is located on the condenser coil return bend. See Fig. 13 and 14. It controls the staging of the unit condenser fans based on the condensing temperature of the refrigerant at the designated position on the condenser coil.

T4 — SATURATED CONDENSING TEMPERATURE, CIRCUIT 2 — This thermistor is located on the condenser coil return bend. See Fig. 13 and 14. It controls the staging of the unit condenser fans based on the condensing temperature of the refrigerant at the designated position on the condenser coil.

T10 — RESET TEMPERATU RE — This thermistor is used only if the accessory temperature reset package is used. It provides occupied space temperature information to the processor, which determines whether or not reset is required. The thermistor is remotely mounted outside the unit in the conditioned space.

The relay board is used to control 24-v

The display board is located in the

The processor uses up to 5 thermistors to

Table 3 — Output Pin and Terminal Assignments

OUTPUT PIN-

TERMINAL

J6-1

J6-2

J6-3

J6-4

J6-5

J6-6

J6-7 J6-8 J5-1 J5-2

J5-3

J5-4

J5-5

LEGEND *Circuit 1.

ALM — CR — ECR — EOR — HIR — IFC — OFC — U—

Alarm Control Relay Economizer Close Relay Economizer Open Relay Heat Interlock Relay Indoor (Evaporator) Fan Contactor Outdoor (Condenser) Fan Contactor Unloader

NAME RATING DEVICE

Stage 1 Compressor Relay (K1)*

Stage 2 Compressor Relay (K2)*

Stage 3 Compressor Relay (K3)*

Compressor Relay (K4)† Not Used Stage 5

Compressor Relay (K5)† Stage 6

Compressor Relay (K6)† Economizer Open Relay (K7) EOR Economizer Close Relay (K8) ECR Supply Fan Relay (K9) Morning Warm-Up Relay (K10) HIR Stage 1 Condenser

Fan Relay (K11) Stage 2 Condenser

Fan Relay (K12) External Alarm Relay (K13) ALM

†Circuit 2.

**U2 is not used on 044 units.

††OFC2 on 034-048 units; OFC3 on 054-104 units.

Used on 054-104 units only.

24 vac

115 vac

CR1

U2**

CR2

Not Used

IFC

OFC2/OFC3††

OFC4||

LEGEND

Control Relay

CR —

Terminal Pin Connectors

J—

Relay

K—

Fig. 5 — Relay Board

P1 SUPPLY AIR SET POINT POTENTIMETER

TWO-DIGIT DISPLAY

DISPLAY BUTTON

Fig. 6 — Display/Set Point Board

Compressor Operation

CONTROL RELAY (CR) — This relay provides information to the processor about compressor operation (one control relay per compressor). The relay controls and protects the compressor and also controls the crankcase heater.

A control signal to check the safety s tatuses and to sta rt the compressor is sent from the relay board. This signal travels through all of the safeties: the high-pressure switch, and the internal protector (where used) and on to the control relay coil. Once the control relay coil has been energized, the control re lay completes a feedback circuit for the processor, informs the processor of the status of the compressor safeties, energizes the compressor contactor coil, and deenergizes the crankcase heaters. A fault will be detected by the processor if the control relay opens during operation or startup. The processor will lock the compressor or the circuit off by deenergizing the appropriate relay(s) on the relay board and energizing an alarm signal.

Accessory Board —

(factory supplied) in the VAV rooftop units. See Fig. 15. This board is located in the control box of each unit. Each board has a prewired connector supplied with it to connect directly to the processor board. It has 3 potentiometers: P3, P5, and P6.

The accessory board is standard

P3 — RESET LIMIT — The processor board is programmed for occupied space temperature reset. In order for reset to work, the accessory temperature reset board must be used. Potentiometer P3 is the maximum set point temperature to which the supply air can be reset.

P5 — ECONOMIZER MINIMUM POSITION — This potentiometer controls the set point for the minimum position of the economizer.

P6 — MORNING WARM-UP TEMPERATURE — This potentiometer controls the morning warm-up temperature set point.

Single-Step Demand Limit —

The single step demand limit provid es a means to li mit the capaci ty of the VAV unit using an external switch. Single step demand limit will limit the compressor displacement based on the ratio of the wiper arm to the full scale resistance. The exact percentage of capacity reduction differs depending on the number of capacity steps.

A 3-wire, 5 to 20 Kohm, field-supplied potentiometer (P4) is required for this option. The potentiometer should be wired to the processor J3 connections. In order to control the demand limit, the wiper arm of the potentiometer should be switched open and closed based on the demand limit requi rement. The control switch is also field-supplied and installed.

If the wiper arm wire is open, all capacity stages can be used. When the wiper ar m wire is closed, the capacity is reduced by the amount set on potentiometer P4.

Demand Limit Control Module (DLCM) —

The DLCM provides a 2-step demand limit control using an external switch. The first step is between 50% and 100% of the maximum compressor displacement. See Fig. 16. The second step is between 0% and 49% of the maximum compressor displacement. The exact percentage differs depending on the number of capacity steps.

T wo adjustable potentiometers are used to set the 2 demand limit points. Potentiometer P1 is used to set a demand limit between 50% and 100% of the unit capacity. Potentiometer P2 is used to set a demand limit between 0% and 49% of unit capacity.

If no power is supplied to the demand limit control module, all capacity stages can be used. When power is supplied to terminal IN1 only, the first step of the demand limit control is energized and the capacity is reduced by the amount set on potentiometer P1. When power is supplied to terminal IN2 only, or to both IN1 and IN2, the capacity is reduced by the amount set on potentiometer P2.

GAS SECTION

(48FK,JK ONLY)

HORIZONTAL SUPPLY SECTION

(50FY,JY ONLY) AND EXTENDED

PLENUM SECTION (50FKX,FKY,JKX,JKY)

Fig. 7 — Thermistor T1 Location, 48FK,JK, 50FY,JY and 50FKX,FKY,JKX,JKY 034-048 Units

FAN DISCHARGE/ELECTRIC HEAT SECTION

Fig. 8 — Thermistor T1 Location, 50FK,JK034-048 Units

GAS SECTION

(48FK,FM,JK)

HORIZONTAL SUPPLY SECTION (50FS,FY,JY)

AND EXTENDED

PLENUM SECTION (50FKX,FKY,FMX,FMY,JKX,JKY)

Fig. 9 — Thermistor T1 Location, 48FK,FM,JK, 50JY and

50JKX,JKY 054-074 Units and 50FKX,FKY,FMX,FMY and 50FS,FY054-104 Units

FAN DISCHARGE/ELECTRIC HEAT SECTION

Fig. 10 — Thermistor T1 Location, 50FK,JK054-074 Units

STANDARD

Fig. 13 — Thermistor T3 and T4 Locations,

Size 034-048 Units

FILTERS

BAG

FILTERS

Fig. 11 — Thermistor T2 Location, Size 034-048 Units

STANDARD FILTERS AND

PLEATED FILTERS

BAG FILTERS

(054-074 Only)

Fig. 12 — Thermistor T2 Location, Size 034-048 Units

ENTHALPY CONTROL 48FK,JK and 50FK,FY,JK,JY Units

— Outside air enthalpy control is standard with the factory-installed economizer option. Enthalpy is sensed by a controller located behind the end outside air hood. The control can be accessed by removi ng the upper hood filter. See Fig. 17.

48FM and 50FM,FS Units

— The control is locat ed on the metal upright between the two economizer hoods, on the right hand side of the unit, and can be accessed by removing the filter on either economizer hood.

DIFFERENTIAL ENTHALPY — Added efficiencies in economizer control can be gained by installing a differential enthalpy sensor in the return air duct. When differential enthalpy control is installed, the economizer control will use the air stream with lower enthalpy (outside air or return air) to provide for lower compressor operating costs during integrated economizer cycle operation. The differential enthalpy sensor is installed in t he re turn -air duc t.

Economizer —

Economizer control is used to control the outside and return air dampers of the unit, to satisfy space cooling demand using all outside air (when permitted), and to satisfy cooling in conjunction with compressor operation (when conditions permit). During Occupied periods without cooling demand, the outside-air dampers will be at the user-configured Minimum Damper Position (at P5 on accessory board). During Unoccupied periods, the outside-air dampers will be closed.

The economizer is a standard feature on 48FM and 50FM,FS units and is available as a factory-installed option on 48FK,JK and 50FK,FY,JK,JY units.

The user can install an ac cessory differential enth alpy sensor to enhance economizer control. Refer to the installation section for field wiring of the sensor.

054 UNITS

064, 074, 078 UNITS

088, 104 UNITS

Fig. 14 — Thermistor T3 and T4 Locations, Size 054-104 Units

LEGEND

Fig. 18 — Variable Frequency Drive,

Sizes 034-048 and 078-104

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

ECON — MIN — P— VAV —

Economizer Minimum Potentiometer Variable-Air Volume

Fig. 15 — Accessory Relay Board

(Standard; Factory Supplied)

The unit is supplied with a pressure transducer capable of measuring from 0.0 to 5.0 in. wg. The pressure transducer wi ll 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 desi red static pressure set point. The VFD is factory set at 2.5 in. wg duct static pressure. Refer to the Operating Sequence 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 configurations 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.

High Capacity Modulating Power Exhaust Variable Frequency Drive (48FM and 50FM,FS Units Only) —

to modulate the power exhaust fan motor no. 1 and stage the power exhaust fan motor no. 2 in order to maintain building static pressure. The PE VFD is loc ated at the re turn air end of the unit of the opposite side from the auxiliary control box and can be accessed by opening the access door.

The unit is supplied with a pressure transducer capable of measuring from –0.5 to +0.5 in. wg. The pressure transducer will send a 4 to 20 mA signal to the PE VFD to modulate the speed of the power exhaust motor no. 1 and also stage on/off the power exhaust motor no. 2 to precisely maintain the desired building pressure set point. The PE VFD is factory set at 0 in. wg. Refer to Operating Sequence section for more information on the PE VFD.

The PE VFD has been programmed and wired at the factory for this application. No further adjustments (except for Building Pressure Set Point) should be necessary at start-up. Factory jumper wire configurations are shown in the Power Exhaust Variable Frequency Drive sec tion in the Troubleshooting section on page 55.

The power exhaust VFD (PE VFD) is used

LEGEND

IC — IN — P— RTN —

Integrated Circuit Input Potentiometer Return

Fig. 16 — Two-Step Demand Limit Module

Fig. 17 — Enthalpy Sensor Location

(48FK,JK and 50FK,FY,JK,JY Units Only)

Supply Fan Variable Frequency Drive (VFD) —

airflow 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 accessed by opening the fan section access door.

The optional VFD is used to modulate supply fan

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

Temperature Reset —

Accessory temperature reset allows 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 sat isfied, 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 capacity stages to m ai nta in user-established supp ly - a ir set point temperature. When VAV units are also equipped with optional supply duct pressure controls (either inlet guide vanes [IGV] or variable frequency drive package), the unit also senses an increase in duct static pressure and responds by closing IGV dampers or slowing fan wheel speed to maintain user-configured set points for supply duct pressure. Allowing the supply-air temperature to be reset to a higher value maintains air c irculation in the space without costly overcooling.

The accessory package is required for temperature reset.

The accessory includes:

• thermistor T10, to monitor space temperature

• reset temperature potentiometer P7, to establish start

temperature for reset operation

• reset limit potentiometer P3, to establish maximum level

of modified supply-air temperature

More than one space sensor may be used if an average space temperature is desired for initiating temperature reset. Refer to installation section for sensor part number and wiring schematic.

Temperature reset will start when space temperature (at T10) drops to the set point at P7. When Temperature Reset is active, the LED (light-emitting diode) display will show code 21 . Automatic adjustment of supply-air temperature set point will end when modified SASP equals reset limit set point at P3. (See formula for automatic modification of SASP in Controls Installation, Space Te mperature Reset section on this page.)

CONTROLS INSTALLATION

The VAV units may be used in applications with additional control features, options, or accessories. Refer to the appropriate accessory installation instructions for more information on installing that accessory. Unit control box component arrangement is shown in Fig. 20-22. Control options and accessories available for VA V units are:

• smoke cont rol modes

• differential enthalpy sensor

• electric heaters (sizes 034-074 only)

• modulating power exhaust

• Motormaster

• space temperature reset

• night setback thermostat (field-supplied)

• single step demand limit

• two-step demand limit

• inlet guide vanes

• variable frequency drive

• variable frequency drive remote display kit

Control Wiring —

must be wired in to control when unit will go into and out of Occupied mode. Connect switch or timeclock between terminals 1 and 2 on terminal block 3 (siz es 034-048) or terminal block 4 (sizes 054-104) in unit control box. See Fig. 23. The circuit potential is 24 v.

Variable air volume units equipped wit h warm-up heat require that room terminals be controlled to go fully open when unit goes into the Heating mode. Heating interlock relay (HIR) is provided for this function. The relay is located in the unit

I control

A switch or timeclock (field supplied)

control box. When unit goes into Heating mode, interlock relay is energized providing switch closure or opening (depending on how field power source is set up) to open the room terminals. Field connections for interlock relays are termina ls 3 and 4 (for normally open contacts) and terminals 3 and 7 (for normally closed contacts) on terminal block 3 (sizes 034-048) or terminal block 4 (sizes 054-104). See Fig. 24. Note that a fieldsupplied power source is required.

There are no required 115-volt field wiring connections, therefore no provisions have been made in the unit for running 115-volt wiring. If any of the field-installed options requiring 115-volt connections are desired, the unit must be modified in the field for 115-volt wiring.

NIGHT SETBACK THERMOSTAT — Wire field-supplied thermostat (suitable for 24-v circuit) between terminals 1 and 2 on terminal block 3 (sizes 034-048) or terminal block 4 (sizes 054-104). This thermostat is used to bypass the timeclock occupied/unoccupied switch and is used to operate unit during unoccupied times at more economical temperatures. (See Fig. 23.)

SP AC E TEMPERATURE RESET AC CESSORY (50DJ900021) — Consists of a thermistor (T10) and a rese t board with a potentiometer (P7) that is used to set space temperature at which reset starts. Mount reset boar d in unit control box or ot her convenient place. Wire thermistor in series with P7 and connect to terminals 12 and 15 on terminal block 3 (sizes 034-048) or terminal block 4 (sizes 054-104) in unit control box. If there is a long run to conditioned space, it is nece ssary t o splice additional wire to thermistor. The reset board has 2 pressur e connectors for field wiri ng. (See Fig. 25.)

Space Temperature Reset

INSTALLATION — Install the accessory temperature reset package in accordance with instructions provided with the accessory kit.

Mount the reset board in the unit control box (or other suitable location) per instructions.

Locate the thermistor T10 in a suitable location in the occupied space per instructions.

Wire T10 to the reset board and to the unit control terminal block per Fig. 25. Wire the other terminal on the reset board to the unit control terminal block per Fig. 25.

If multiple sensors are required to average the space temperature, see Fig. 26. Use only Carrier Part Number HH79NZ014 sensor, in arrangements of 4 or 9 sensors, with total wiring not to exceed 1000 ft.

To enable reset function, change DIP (dual in-line package) switch 2 to position ON. (Disconnect control power before changing DIP switch positions; reconnect power after all changes have been made.)

CONFIGURATION — Set points for reset operation are established at potentiometers P7 and P3 (on the reset board).

Potentiometer P7 at which reset function will start). Maximum of 80 F, minimum 0° F. Set bel ow normal room cooling set point level to sense overcooling in the occupied space.

NOTE: It is difficul t to accura tely set t he P7 potenti ometer to the desired set point. Use the procedure below.

Proper setting of the P7 potentiometer may be made on a resistance basis. The microprocessor initiates reset when it detects a resistance of the thermistor plus the potentiometer of 13,084 ohm. The potentiometer set point may be calculated using the following formula:

= 13,084 – T10

Where:

= the desired set point of the P7 potentiometer in ohms

T10

= the resistance of the T10 thermistor for the desired

— Reset temperature set point (temperature

set point

Fig. 20 — Unit Control Box Arrangement, Sizes 034-048

Fig. 21 — Unit Control Box Arrangement, Sizes 054-078

Fig. 22 — Unit Control Box Arrangement, Sizes 088 and 104

034-048: TB3 054-104: TB4

OCCUPIED/UNOCCUPIED

SWITCH

NIGHT SETBACK THERMOSTAT

NOTES:

1. Occ/Unocc switch closes when occupied.

2. Night setback thermostat closes when in night setback heating.

034-048: TB3 054-104: TB4

Fig. 23 — Occupied/Unoccupied Switch with

Night Setback Thermostat

OPERATING SEQUENCE — If space temperature is above reset set point (T10 > P7), no reset will occur.

If space temperature is equal to or less that reset set point (T10 < P7), the LED will display 20 and reset will begin.

Control will automatically adjust leaving air temperature by the following formula:

MSP = SP + [(P3 - SP) / 3] x (P7 – T10) where: MSP = Modified Leaving-Air Set Point SP = Supply-Air Set Point P3 = Maximum Supply-Air Temperature (reset limit) P7 = Reset Initiation Temperature (reset set point) T10 = Actual Space Temperature 3 = Ratio for reset (F) (fixed parameter)

Table 4 — Thermistor Resistance and Voltage

Drop Characteristics

034-048: TB3 054-104: TB4

FIELD

N.O.

N.C.

SUPPLIED POWER SOURCE

SIGNAL TO ROOM TERMINALS

Fig. 24 — Heat Interlock Relay

034-048: TB3 054-104: TB4

T10

RESET BOARD

Fig. 25 — Accessory Reset Board

EXAMPLE:

T10 desired set point is 70 F .

from Tabl e 4 for 70 F is 5929 ohms.

T10

= 13,084 – 5929

= 7155 ohms

Using an ohmmeter, set the P7 potentiometer to 7155 ohms

to achieve a reset initiation set point of 70 F. Potentiometer P3

— Reset limit set po int (max imu m tem per ature value for modified supply air set point). Maximum of 70 F , minimum 40 F. Set between leaving air set point (P1) and 70 F (maximum range permitted by control).

TEMP

(F)

31.0

32.0

33.0

34.0

35.0

36.0

37.0

38.0

39.0

40.0

41.0

42.0

43.0

44.0

45.0

46.0

47.0

48.0

49.0

50.0

51.0

52.0

53.0

54.0

55.0

56.0

57.0

58.0

59.0

60.0

61.0

62.0

63.0

64.0

65.0

66.0

67.0

68.0

69.0

70.0

71.0

72.0

73.0

74.0

75.0

76.0

77.0

78.0

79.0

80.0

RESISTANCE

(Ohms)

16813.8 3.582

16345.7 3.553

15892.2 3.523

15452.7 3.494

15026.7 3.464

14613.9 3.434

14213.6 3.404

13825.5 3.373

13449.2 3.343

13084.2 3.312

12730.1 3.281

12386.6 3.250

12053.3 3.219

11730.0 3.187

11416.1 3.156

11111.5 3.124

10815.8 3.093

10528.7 3.061

10250.0 3.029

9979.3 2.997

9716.5 2.965

9461.3 2.933

9213.4 2.901

8972.6 2.869

8738.6 2.837

8511.4 2.805

8290.6 2.772

8076.1 2.740

7867.7 2.708

7665.1 2.676

7468.3 2.644

7277.1 2.612

7091.2 2.581

6910.6 2.549

6735.1 2.517

6564.4 2.486

6398.6 2.454

6237.5 2.423

6080.8 2.391

5928.6 2.360

5780.6 2.329

5636.8 2.299

5497.0 2.268

5361.2 2.237

5229.1 2.207

5100.8 2.177

4976.0 2.147

4854.8 2.117

4736.9 2.088

4622.4 2.058

VOLTAGE

DROP (v)

SIZES 034-048

TB3

TO ACCESSORY SPACE TEMPERATURE RESET CONTROL BOARD

SIZES 054-104

TB4

SIZES 034-048 TB3

TO ACCESSORY SPACE

TEMPERATURE RESET

CONTROL BOARD

SIZES 054-104 TB4

RED

BLK

RED BLK

RED

BLK

RED

BLK

SENSOR 1 SENSOR 2 SENSOR 3 SENSOR 4

RED

BLK

RED

BLK

SPACE TEMPERATURE RESET — 4 SENSOR AVERAGING APPLICATION

RED

BLK

SENSOR 1

RED

BLK

SENSOR 2

RED BLK

SENSOR 3

RED

BLK

SENSOR 4

BLK

RED

NOTE: Sensor part number is HH79NZ014.

SPACE TEMPERATURE RESET — 9 SENSOR AVERAGING APPLICATION

Fig. 26 — Space Temperature Sensor Averaging

Demand Limit —

The demand limit function provides a means to limit the cooling capacity of the VAV unit using an external discrete switch function. When enabled by the closure of the external switch, the control will limit the available compressor staging capacity according to user set points established at demand limit potentiometer(s).

The unit controls support two types of demand limit: single-

step and 2-step control. SINGLE-STEP DEMAND LIMIT — This function wi ll limit

the total compressor staging based on the ratio of the set point potentiomete r’s wiper arm posit ion to the full sca le resistanc e of the potentiometer. The exact percentage of capacity reduction differs depending on the number of capacity steps.

A field-supplied potentiometer and control switch are required for this function. See installation section for specification on potentiometer and field wiring.

TWO-STEP DEMAND LIMIT — Two-step demand limit is provided with the installation of the accessory Demand Limit

SENSOR 6SENSOR 5

RED

BLK

SENSOR 8SENSOR 7 SENSOR 9

RED

BLK

Control Module kit plus installation of 2 field-supplied control switches (SPST-NO each). This accessory control provides for a first step reduction of 50% to 100% of the maximum compressor staging; the second step provides for reduction between 0% and 49%. The exact percentage of capacity reduction differs depending on the number of capacity steps.

When demand limit is active, the LED display will show

code 22 . INSTALLATION Single-Step Demand Limit

— A 3-wire 5 to 20 K-ohm potentiometer must be field-supplied and installed. A singlepole normally open switch is also required (field-supplied and -installed). Loca te the potentiometer (desi gnated P4) and the switch in a suitable location (external from the unit or in the unit control box).

Connect the potentiometer end terminals to terminals 8

034-048: TB3 054-104: TB4

5-20K POTENTIOMETER (P4)

SWITCH

Fig. 27 — Single-Step Demand Limit

Fig. 28 — Two-Step Demand Limit Module

NOTES:

1. Demand limit switches are field supplied and wired.

2. Demand limit control module terminal blocks will accept up to 12-gage wire.

3. is field wiring.

Fig. 29 — 115-Volt Field Wiring to Accessory

2-Step Demand Limit Control Module

and 9 on control terminal block TB3 (sizes 034-048) or TB4 (sizes 054-104) (see Fig 27). Connect the switch terminals to the potentiometer wiper arm terminal and to terminal 10 on TB3 or TB4.

To ena ble demand limit function, change DIP switch 5 to position ON. (Disconnect control power before changing DIP switch positions. Reconnect power after all changes have been made.)

Set the potentiometer P4 to desired capacity reduction value. Two-Step Demand Limit

— Install the demand limit control module (DLCM) according to the installation instructions provided with the accessory. Disconnect existing leads at connector J3 on the processor board (see instructions) and connect the plug from the DLCM harness to connector J3.

Connect the field input control power wires (from the external control relays) at the terminal strips marked IN1, RTN1, IN2 and RTN2 (see Fig. 28 and 29).

To ena ble demand limit function, change DIP switch 5 to position ON. (Disconnect control power before hanging DIP switch positions. Reconnect power after all changes have been made.)

Set the potentiometers DLCM-P1 and DLCM-P2 to desired capacity reduction values.

Check the operation of demand limit function by using the Quick Te st procedures.

CONFIGURATION Single-Step Demand Limit

— Field-installed potentiometer P4 establishes capacity reduction value for demand limit operation. Set this potentiometer between 0% and 100%. The exact percentage of capacity reduction differs depending on the number of capacity steps.

Two-Step Demand Limit

— Potentiometer P1 and P2 (located on the accessory demand limit control module) establish the capacity reduction values for each step of demand limit. Set potentiometer DLCM-P1 between 50% and 100%. Set potentiometer DLCM-P2 between 0% and 49%. The exact percentage of capacity reduction differs depending on the number of capacity steps.

OPERATING SEQUENCE Single-Step Demand Limit

— If the field control switch to the wiper arm terminal is open, all capacity stages will be available (no demand limit in effect). When the field control switch is closed, the compressor cooling capacity is reduced by the amount set on potentiometer P4.

When demand limit is in effect, the LED display will show code 22 . If a potentiometer setting or input is out of range, the control will terminate the demand limit function and show code 84 at the display LED.

Two-Step Demand Limit

— If the field control switches are both open (no power supplied to the Demand Limit Control Module), all capacity stages will be available (no demand limit in effect). When control power is supplied to terminal IN1 only (field switch SW1 closes), the first step of the demand limit is energized and the compressor cooling capacity is reduced by the amount set on potentiometer DLCM-P1. When control power is supplied to terminal IN2 (field switch SW2 closes), the second step of the demand limit is energized and compressor cooling capacity is reduced by the amount set on potentiometer DLCM-P2.

Control From Remote Building Management System (BMS) —

municating control system, and it cannot be acce ssed directly by a DDC (Direct Digital Control) control system (or by a BACnet communication system). However, it is possible to control some functions of these units via 4 to 20 mA or 2 to 10 vdc signals and discrete inputs (relay contact closures).

Functions that can be managed from or accessed from an

external control system include:

• Occupied/Unoccupied Status

• Night Setback Control

• Unit Supply Air Set Point Adjustment

• Demand Limit (1-stage or 2-stage)

• Supply Duct Pressure Set Point Adjustment

• External Alarm Signal Remote control of the economizer cycle on these units is not

recommended. Refer to the Operating Sequence section on page 35 for a discussion on the economizer cycle operation.

The unit control system is not a com-

OCCUPIED/UNOCCUPIED — The unit control system will initiate normal occupied mode functions (including Morning W arm-up, Economizer Minimum Position, and Cooling Cycle) whenever a contact closure is made that emulates the normal timeclock contacts. See Fig. 23. (‘‘Occupied/Unoccupied Switch’’). The contact closure from the BMS must be an isolated contact set, normally open, and suitable for 24 volts AC pilot duty .

NIGHT SETBACK CONTROL — Night setback control is used to control the space to a set point level that is typically lower than during normal occupied periods (Heating Only mode). Some applications also require a limitation on the maximum space temperature during unoccupied periods (Cooling mode). Both modes are possible by closing the same contacts used in the Occupied/Unoccupied control, or by installing a dedicated contact set in parallel with the Occupied/ Unoccupied control contacts, and using the BMS space temperature sensing system and its logic to determine when to initiate unit operation.

Once the unit operation has been initiated by the BMS contact closure, the unit operates in its normal occupied mode manner, initiating morning warm-up if needed (as sensed by return air temperature to the unit) or cooling (controlling to current SASP value). The Night Setback Control contacts will interrupt normal unit operation when the BMS senses that spac e temperatures have returned to unoccupied set point levels, and the unit will shut down normally.

The contact closure from the BMS must be an isolated contact set, normally open, suitable for 24 volts AC pilot duty.

NOTE: If the rooftop unit is equipped with a VFD and night setback cooling operation is intended, the fan system must be controlled to pe rmit FULL SUPPLY FAN AIR DELIVERY during unoccupied cooling operation. This is most conveniently attained by replicating the HIR relay function of the rooftop unit. An HIR control sequence will force all room terminals to their minimum heating CFM position, thus assuring adequate airflow through the rooftop unit during night setback cooling operation. During night setback cooling operation, the return-air temperature (RAT) will be well above normal levels. The higher RAT means that the air temperature leaving the evaporator coil will also be well above normal levels. This situation is interpreted by the unit control system as a demand for additional cooling stages. The unit control responds to this demand by bringing on more stages, until typically all stages are active. If the VFD is not working in-step with the refrigeration system demand, it is possible to produce low suction pressures and local frosting on the evaporator coil during the night setback cooling operation.

UNIT SUPPLY AIR SET POINT ADJUSTMENT — The minimum Supply Air Set Point (SASP) temperature is established by the setting at Potentiometer P1 on the unit display board (see Fig. 6). The control point can also be adjusted upward by emulating the function of the accessory Space Temperature Reset package. The BMS can be used to cause this reset by adjusting the resistance value in a variable resi stance transducer with a 4 to 20 mA or 2 to 10 vdc signal generated by the BMS.

This emulation requires the following field-supplied parts:

• Variable resistance transducer (Kele RES-1 or equiva-

lent, range 0 to 1000 ohms)

• Series resistance with potentiometer, suitable for manual

adjustment to 12.5 to 13.0 k-ohms total resistance

Field Connections (see Fig. 30) with manual potentiometer and variable resistance transducer in series.

Connect wiring to rooftop unit at:

Size 034-044: TB3-12 and TB3-15 Size 054-104: TB4-12 and TB4-15

— Connect fixed resistance

Configuration

1. Set DIP switch no. 2 to ON.

2. Adjust manual potentiometer to 12.6 to 12.8 k-ohm.

3. Configure transducer for job site input signal from BMS.

4. Adjust Potentiometer (P3) on the rooftop to MAXIMUM SASP value (typically 65 to 70 F). The maximum P3 SASP

control limit is 70 F. Operation

SASP upward) when the sum of the resistance (fixed resistance + potentiometer + transducer) exceeds 13.1 k-ohm. Once reset is initiated, full range of reset (P3 setting minus configured SASP) will be reached with 500-ohm increase in transducer resistance (TR).

During Reset mode operation, Code 21 will appear on unit

display board. Formula: MSP = SASP +

(P3 — SASP)

[

MSP: Modified SASP (S ASP plus Reset ) TR: Resistance at transducer

R@13.1: TR required to reach 13.1 k-ohm start level DEMAND LIMIT (1-STAGE OR 2-STAGE) — Both of the

Demand Limit functions on the units rely on external switches to initiate the reset functions. Contact closures by the BMS can be used in place of these switches. Contacts must be isolated and suitable for 115-vac pilot duty operation.

For Single-Step Demand Limit, emulate function of switch

SW with contact closure controlled by the BMS. Set potentiometer P4 manually at the unit control box. Alternatively, potentiometer P4 might also be emulated by a variable resistance transducer, with the BMS now able to adjust the amount of demand limit.

For 2-Step Demand Limit, install the accessory Demand

Limit Control Module (DLCM) according the instructions on page 18. Replace switch functions Switch 1 and Switch 2 with contact closures controlled by the BMS (see Fig. 29).

Follow unit control configuration instructions in the De-

mand Limit section on page 18. SUPPLY DUCT PRESSURE SET POINT ADJUSTMENT

— Supply duct pressure set point adjustment from a remote BMS is possible when the unit has been equipped with a factory-option VFD (variable frequency drive). There are two methods available:

• Direct 4 to 20 mA signal

• DDC direct to the VFD Direct 4 to 20 mA Signal

the factory-installed VFD receives a 4 to 20 mA signal from the Duct Pressure (DP) transducer which indicates current supply duct pressure. The VFD then determines the appropriate fan speed (using its internal PID logic feature) and adjusts its output to the supply fan motor to suit. It is possible to emulate this 4 to 20 mA control signal by the BMS, which will transfer control of the VFD to the BMS.

NOTE: When providing a direct 4 to 20 mA signal to the VFD from a BMS with DP logic, disable the PID (proportion integrated derivative calculation process) feature of the VFD.

DDC Direct to the VFD boards are available for the VFDs that permit direct communication between the VFD and several BMS communication systems. Contact your Carrier representative for information on selecting an appropriate accessory interface board and the name of the local service office (for sale and installation of the accessory boards).

— Configure as follows:

— Unit will initiate SASP Reset (adjust configured

(0.6 F)

(3) (100 ohm)

— Several accessory interface

X (TR — R@13.3)

— During normal unit operation,

]

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