Carrier 48DK024 - User Manual

Controls, Operation,
and Troubleshooting
CONTENTS
Page
INTRODUCTION ............................2-12
VAV Control System ..........................2
Processor Board .............................2
• P1 — LEAVING-AIR SET POINT
• P2 — ECONOMIZER POSITION
• P3 — RESET LIMIT
• P4 — DEMAND LIMIT
• P5 — ECONOMIZER MINIMUM POSITION
• P6 — WARM-UP SET POINT
• P7 — RESET TEMPERATURE
• PROCESSOR BOARD OUTPUTS
• CONFIGURATION HEADER AND DIP SWITCH
ASSEMBLY
Relay Board .................................5
Display Board ...............................5
Thermistors .................................5
• T1 — LEAVING-AIR SET POINT THERMISTOR
• T2 — RETURN-AIR THERMISTOR
• T3 — SATURATED CONDENSING
TEMPERATURE, CIRCUIT 1
• T4 — SATURATED CONDENSING
TEMPERATURE, CIRCUIT 2
• T10 — RESET TEMPERATURE
Compressor Operation .......................7
• CONTROL RELAY (CR)
Accessory Board ............................7
• P3 — RESET LIMIT
• P5 — ECONOMIZER MINIMUM POSITION
• P6 — MORNING WARM-UP TEMPERATURE
Single-Step Demand Unit ....................12
Demand Limit Control Module (DLCM) .......12
OPERATING INFORMATION ................12-21
Digital Display ..............................12
• CODES 0 THROUGH 6, CAPACITY STEPS
• CODES 20 THROUGH 30 AND 88, OPERATIONAL
STATUS
• CODES 51 THROUGH 87, OVERLOAD
INFORMATION
Operating Sequence ........................13
• SIZE 024-034 AND 054-074 UNITS
• SIZE 044 UNITS
Head Pressure Control ......................14
• SIZE 024-030 UNITS
• SIZE 034-074 UNITS
Inlet Guide Vanes ...........................14
Temperature Reset ..........................14
Demand Limit Control .......................17
Building Pressurization Mode ................17
Smoke Purge Mode .........................17
Units Equipped with Static Pressure Control
Option ....................................17
Page
Quick Test Program .........................17
SERVICE AND TROUBLESHOOTING ........21-32
Inlet Guide Vane Motor (Units with Inlet Guide
Vanes and Static Pressure Control Option) ..21
Modulating Power Exhaust Differential
Pressure Switch ............................21
• SIZE 024-030 UNITS
• SIZE 034,044 UNITS
• SIZE 054-074 UNITS
Inlet Guide Vane Differential Pressure Switch
(Units with Inlet Guide Vane and Static
Pressure Control Option) ...................21
• SIZE 024-030 UNITS
• SIZE 034,044 UNITS
• SIZE 054-074 UNITS
Differential Pressure Switch Set Point and Null
Span (Units Equipped with Inlet Guide Vane
and Static Pressure Control Option) ........22
Differential Pressure Switch Set Point and Null
Span (Units Equipped with Modulating Power
Exhaust Option) ...........................23
VAV Diagnostic Information ..................23
• CODES 51 AND 55: 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: SUPPLY-AIR TEMPERATURE 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
Electronic Controls Checkout ................25
• PROCESSOR BOARD CHECKOUT
• RELAY BOARD TROUBLESHOOTING
• DISPLAY BOARD CHECKOUT
• ACCESSORY BOARD CHECKOUT
• TWO-STEP DEMAND LIMIT CONTROL MODULE
(DLCM) TROUBLESHOOTING
Thermistor Troubleshooting .................29
Control Wiring ..............................29
48DK024-074
50DK,DY024-074
Variable-Air Volume Rooftop Units
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. 564-878 Printed in U.S.A. 48/50DK,DY-1T Pg 1 4-96 Replaces: New

Summary

INTRODUCTION

VAV Control System

Describes the VAV control system's components and functions.

Processor Board

Details the central processing unit of the VAV control system.

Relay Board

Explains the function of the relay board in controlling loads.

Display Board

Describes the display board for status and diagnostic information.

Thermistors

Explains the role of thermistors in sensing system temperatures.

Compressor Operation

Details how compressors are controlled and monitored by the system.

Accessory Board

Describes the function and components of the accessory board.

Single-Step Demand Limit

Covers the single-step demand limit feature for capacity reduction.

Demand Limit Control Module (DLCM)

Details the DLCM for two-step demand limiting.

OPERATING INFORMATION

Digital Display

Explains the 2-digit LED display for operational and diagnostic codes.

Operating Sequence

Describes the step-by-step operation of the unit during various modes.

Quick Test Program

Unit Configuration and Switch Check

Verifies unit configuration and DIP switch settings.

Thermistor and Set Point Potentiometer Checks

Checks the functionality of sensors and set point potentiometers.

Output Relay Check

Tests the output signals for various relays.

SERVICE AND TROUBLESHOOTING

Inlet Guide Vane Motor

Discusses the inlet guide vane motor and its location for control.

Modulating Power Exhaust Differential Pressure Switch

Explains the differential pressure switch for modulating power exhaust control.

Inlet Guide Vane Differential Pressure Switch

Details the differential pressure switch for inlet guide vanes.

Differential Pressure Switch Set Point and Null Span

Covers setting the pressure switch parameters for vanes.

VAV Diagnostic Information

Explains diagnostic codes and their meanings for VAV systems.

Electronic Controls Checkout

Guides on troubleshooting control boards and system components.

Carrier 48DK024 Specifications

General

Energy Efficiency Ratio (EER)	11.0
Refrigerant	R-410A
Voltage	208/230V
Phase	3
Compressor Type	Scroll
Stages	Single
Cooling Capacity	24, 000 BTU/h