Carrier 48DK024 Controls Operation And Troubleshooting
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Carrier 48DK024 Controls Operation And Troubleshooting

Carrier 48DK024 Controls Operation And Troubleshooting

Variable-air volume rooftop units
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INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
VAV Control System . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Processor Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
• P1 - LEAVING-AIR SET POINT
• P5 - ECONOMIZER MINIMUM POSITION
• P7 - RESET TEMPERATURE
• PROCESSOR BOARD OUTPUTS
Relay Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Display Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Thermistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
• T1 - LEAVING-AIR SET POINT THERMISTOR
Compressor Operation . . . . . . . . . . . . . . . . . . . . . . . 7
Accessory Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
• P5 - ECONOMIZER MINIMUM POSITION
Single-Step Demand Unit . . . . . . . . . . . . . . . . . . . . 12
OPERATING INFORMATION . . . . . . . . . . . . . . . . 12-21
Digital Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
STATUS
Operating Sequence . . . . . . . . . . . . . . . . . . . . . . . . 13
Head Pressure Control . . . . . . . . . . . . . . . . . . . . . . 14
Inlet Guide Vanes . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Temperature Reset . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Demand Limit Control . . . . . . . . . . . . . . . . . . . . . . . 17
Building Pressurization Mode . . . . . . . . . . . . . . . . 17
Smoke Purge Mode . . . . . . . . . . . . . . . . . . . . . . . . . 17
Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book 1 1
PC 111
Tab
1a 1b
Controls, Operation,
and Troubleshooting
CONTENTS
Page
Catalog No. 564-878
Printed in U.S.A.
Variable-Air Volume Rooftop Units
Quick Test Program . . . . . . . . . . . . . . . . . . . . . . . . . 17
SERVICE AND TROUBLESHOOTING . . . . . . . . 21-32
Inlet Guide Vane Motor (Units with Inlet Guide
Pressure Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
• SIZE 024-030 UNITS
• SIZE 034,044 UNITS
• SIZE 054-074 UNITS
(Units with Inlet Guide Vane and Static
Pressure Control Option) . . . . . . . . . . . . . . . . . . . 21
• SIZE 024-030 UNITS
• SIZE 034,044 UNITS
• SIZE 054-074 UNITS
Span (Units Equipped with Inlet Guide Vane
Exhaust Option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
VAV Diagnostic Information . . . . . . . . . . . . . . . . . . 23
• CODES 51 AND 55: COMPRESSOR FAILURE
• CODE 70: ILLEGAL UNIT CONFIGURATION
• CODE 82: SUPPLY-AIR TEMPERATURE SET POINT
POTENTIOMETER FAILURE
FAILURE
Electronic Controls Checkout . . . . . . . . . . . . . . . . 25
• PROCESSOR BOARD CHECKOUT
• RELAY BOARD TROUBLESHOOTING
• ACCESSORY BOARD CHECKOUT
(DLCM) TROUBLESHOOTING
Thermistor Troubleshooting . . . . . . . . . . . . . . . . . 29
Control Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
48/50DK,DY-1T
48DK024-074
50DK,DY024-074
Pg 1
4-96
Replaces: New
Page

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Summary of Contents for Carrier 48DK024

  • Page 1: Table Of Contents

    48DK024-074 50DK,DY024-074 Variable-Air Volume Rooftop Units Controls, Operation, and Troubleshooting CONTENTS Page Page Quick Test Program ......17 INTRODUCTION .

  • Page 2: Introduction

    The VAV control system monitors and controls the fol- INTRODUCTION lowing functions of the rooftop unit: This guide contains information on the electronic control • leaving-air temperature (unit capacity) system and control system troubleshooting for the 48DK and • morning warm-up or electric heat (if equipped) 50DK,DY024-074 variable-air volume (VAV) units.
  • Page 3 Table 2 — Pin Terminal Connector J2 Status Switch Several temperature inputs are connected to the proces- sor. There are either 4 or 5 thermistors (depending on the Inputs field-installed accessories) which input temperature data into the processor through pin terminal connector J1. See UNIT SIZE CONNECTOR J2 STATUS SWITCH...

  • Page 4: P3 - Reset Limit

    Table 3 — Potentiometer Inputs and Ranges CONTROL POTENTIOMETER DESCRIPTION LOCATION VALID DEFAULT VALUE RANGE Leaving Air Display 45 F if -22 F < P1 < 45 F 45 to 70 F Set Point Board 70 F if P1 > 70 F OR IF P1 < -22 F Economizer Economizer 0 to 100%...

  • Page 5: Configuration Header And Dip Switch Assembly

    Table 5 — DIP Switches P5 — ECONOMIZER MINIMUM POSITION — This po- tentiometer is on the accessory board (provided standard from the factory) located in the unit main control box. It has both SWITCH FUNCTION FACTORY MEANING SETTING* a valid range and an operational range of 0% to 100%. If a fault condition is detected by the processor, an alarm con- Reset Space or Outdoor-...
  • Page 6 Table 7 — Output Pin and Terminal Assignments UNIT SIZES OUTPUT PIN- NAME RATING TERMINAL 024-030 034-074 Stage 1 J6-1 Compressor Relay (K1)* Stage 2 J6-2 U2** Compressor Relay (K2)* Stage 3 J6-3 Compressor Relay (K3)* Stage 4 J6-4 Not Used 24 vac Compressor Relay (K4)†...

  • Page 7: T2 - Return-Air Thermistor

    The thermistor is remotely mounted outside the unit in the conditioned space. Fig. 8 — Thermistor T1 Location, 50DK024-030 Units Fig. 7 — Thermistor T1 Location, 48DK024-030 Units...
  • Page 8 Fig. 9 — Thermistor T1 Location, 50DY024-030 Units GAS SECTION HORIZONTAL SUPPLY SECTION (48DK ONLY) (50DY ONLY) Fig. 10 — Thermistor T1 Location, 48DK/50DY034,044 Units...
  • Page 9 FAN DISCHARGE/ELECTRIC HEAT SECTION Fig. 11 — Thermistor T1 Location, 50DK034,044 Units GAS SECTION (48DK) FAN DISCHARGE/ELECTRIC HEAT SECTION (50DY) Fig. 12 — Thermistor T1 Location, 48DK/50DY054-074 Units...
  • Page 10 FAN DISCHARGE/ELECTRIC HEAT Fig. 13 — Thermistor T1 Location, 50DK054-074 Units STANDARD FILTERS FILTERS Fig. 14 — Thermistor T2 Location, 024-030 Units Fig. 15 — Thermistor T2 Location, 034,044 Units...
  • Page 11 BAG FILTERS STANDARD FILTERS Fig. 17 — Thermistor T3 and T4 Locations, 034,044 Units Fig. 16 — Thermistor T2 Location, 054-074 Units Fig. 18 — Thermistor T3 and T4 Locations, 054-074 Units...

  • Page 12: Single-Step Demand Unit

    Single-Step Demand Limit — OPERATING INFORMATION The single step de- mand limit provides a means to limit the capacity of the VAV Digital Display — The VAV control system uses a 2-digit unit using an external switch. Single step demand limit will LED display located on the display board to display opera- limit the compressor displacement based on the ratio of the tional information and diagnostic codes.

  • Page 13: Codes 51 Through 87, Overload Information

    Once the initialization period is complete, the supply and Temperature Reset — If the unit is equipped with the ac- return fans begin operation. While the fans are operating, cessory temperature reset package, and DIP switch 2 is in the economizer dampers are closed and return air from the the ON position, the unit will reset the supply-air tempera- building is being circulated.

  • Page 14: Size 044 Units

    Fig. 24. Only Stage 3 Relays K1, K3, and K5 are energized. Compressor Carrier part no. HH79NZ014 sensors are to be used, in ar- no. 1 is running at ⁄ capacity, and compressor no.
  • Page 15 OFM — Outdoor (Condenser) Fan Motor Fig. 21 — Component Arrangement, 024-030 Units OFM — Outdoor (Condenser) Fan Motor Fig. 22 — Component Arrangement, 034,044 Units...
  • Page 16 054,064 UNITS 074 UNIT OFM — Outdoor (Condenser) Fan Motor Fig. 23 — Component Arrangement, 054-074 Units LEGEND TB — Terminal Block Factory Wiring Field Wiring NOTE: For 4-sensor arrangement, wire sensors 1, 2, 4, and 5 as shown. Sensors 3 and 6-9 are not used in a 4-sensor application.

  • Page 17: Demand Limit Control

    Once set point pressure is reached, potentiometer. The Carrier accessory two-step demand limit switch will open and deenergize inlet guide vane motor. If control module utilizes 2 potentiometers and provides 2 steps pressure in supply duct is below 1.9 in.
  • Page 18 LEGEND DPS — Differential Pressure Switch ECR — Economizer Relay — Heating Interlock Relay — Evaporator (Indoor) Fan Contactor — Inlet Guide Vanes — Modulating Interlock Relay MPE — Modulating Power Exhaust — Normally Closed — Normally Open OMR — Occupied Mode Relay PEC —...
  • Page 19 the various options selected by the customer. All DIP IMPORTANT: Once quick test is initiated, display but- switches should be checked and set to proper position for ton must be pressed at least once every 10 minutes for options selected prior to the quick test. See Configuration control to remain in quick test mode.
  • Page 20 Table 9 — Quick Test, Thermistor and Potentiometer Check QUICK NORMAL THERMISTOR OR TEST DESCRIPTION DISPLAY POTENTIOMETER* STEP NO. 1 — Thermistor OK Leaving Air 1.4. 0 — Thermistor Faulty Thermistor (T1) 1 — Thermistor OK Entering Air 1.5. 0 — Thermistor Faulty Thermistor (T2) 024-030 1 —...

  • Page 21: Service And Troubleshooting

    Table 11 — Sensor Resistance Values TEMP RESISTANCE TEMP RESISTANCE TEMP RESISTANCE (Ohms) (Ohms) (Ohms) −60 362,640 11,396 1,020 −55 297,140 9,950 −50 245,245 8,709 −45 202,841 7,642 −40 168,250 6,749 −35 139,960 5,944 −30 116,820 5,249 −25 98,420 4,644 −20 82,665 4,134...

  • Page 22: Differential Pressure Switch Set Point And Null

    Factory setting is 1.9 in. wg. To adjust set point, turn set point adjusting screw (see Fig. 31) clockwise to decrease set point and counterclockwise to increase set point. This switch also has an adjustable null span. The null span is the pres- sure change that can be made without contacts opening or closing.

  • Page 23: Differential Pressure Switch Set Point And Null Span (Units Equipped With Modulating Power Exhaust Option)

    CODES 51 AND 55: COMPRESSOR FAILURE — If con- Differential Pressure Switch Set Point and Null trol relay (CR) opens while compressor should be operating, Span (Units Equipped with Modulating Power compressor will stop and microprocessor will energize alarm Exhaust Option) — The set point range for this switch light and display a code of (depending on com-...

  • Page 24: Codes 59 And 60: Low-Pressure Switch

    CODE 81: RESET THERMISTOR OR POTENTIOM- Processor Board Failure — If hardware that monitors feed- ETER FAILURE — This is a unique code since the reset back switch fails and processor board fails to energize the temperature potentiometer (P7) is in series with the space relay board relay to ON position, an error may be indicated.

  • Page 25: Code 85: Demand Limit Potentiometer (P4) Failure

    3-wire linear potentiometer and an accessory 2-step control The failure will automatically reset once potentiometer re- are available from Carrier. The single-step control has a single turns to normal. If a failure occurs, one of the following is potentiometer while 2-step control has 2 potentiometers the probable cause: (mounted on the demand limit board, see Fig.
  • Page 26 PROCESSOR BOARD CHECKOUT — Refer to Fig. 32 and 33 for location of terminal pins and test points. Step 1 — Check transformer input to the board. Connector J4 is used to connect the control transformer to the processor board. 1.
  • Page 27 Fig. 34 — Relay Board Pin Terminal Connector (J9) Table 13 — Voltage Reading J9 PIN NUMBERS QUICK TEST STEP NO. Fig. 35 — Display Board Pin Terminal Connector (J10) 3 4 5 8 9 10 11 12 13 1.-2.3. 0 12 2.4.

  • Page 28: Display Board Checkout

    Table 14 — Pin Terminal Connector J1 Voltages The following procedure can be used to check out the op- eration of the relays. To do this, turn the control ON/OFF switch to the OFF position, and remove the wiring connec- VOLTAGE TERMINAL (vdc ±...

  • Page 29: Two-Step Demand Limit Control Module

    Table 17 — Terminal Strip J5 Connector Resistance IMPORTANT: Be careful to avoid damaging the con- Reading nector or the processor board when taking the voltage readings. J5 PIN NUMBERS QUICK TEST STEP NO. Test under the following conditions: 1. to 2.5. •...
  • Page 30 LEGEND — Alarm — Pin Terminal Connector — Circuit Breaker — Leaving-Air Temperature — Common — Low-Pressure Switch — Control Relay — Limit Switch — Damper Motor Switch — Motor — Discharge Pressure Switch — Normally Closed — Dummy Terminal —...
  • Page 31 Fig. 36 — Typical Control Wiring; 034,044 Units Shown (cont)
  • Page 32 Fig. 36 — Typical Control Wiring; 034,044 Units Shown (cont) Copyright 1996 Carrier Corporation Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations. Book 1 1 PC 111 Catalog No. 564-878 Printed in U.S.A.

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