Carrier 48DK044 - 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 and System Components

VAV Control System

Overview of the microprocessor-based electronic control system.

Processor Board

Central control unit containing logic and hardware for driving outputs.

Thermistors

Sensors used to measure various system temperatures for control.

Accessory Board

Standard board for potentiometers P3, P5, and P6, located in the control box.

Operating Information and Modes

Digital Display

2-digit LED display for operational info and diagnostic codes.

Operating Sequence

Describes unit operation sequence assuming heat and economizer.

Temperature Reset

Accessory function to reset supply-air temperature based on space conditions.

Demand Limit Control

Method to limit VAV unit capacity via specific settings or modules.

Service and Troubleshooting

Inlet Guide Vane Motor

Location and access for the inlet guide vane motor.

Differential Pressure Switch

Controls inlet guide vanes and modulating power exhaust.

VAV Diagnostic Information

Details diagnostic codes for system problems and their causes.

Electronic Controls Checkout

Procedures to check processor, relay, and display boards.

Thermistor Troubleshooting

Procedures for checking thermistor resistance and voltage.

Control Wiring

Wiring diagrams and assistance for unit control troubleshooting.

Carrier 48DK044 Specifications