Carrier 50DK030 - 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

VAV Control System Fundamentals

VAV Control System Components

Overview of the system's hardware elements including processor, relay, and display boards.

Processor Board Functionality

Details the central control unit's role, its enclosure, and connections.

System Input and Output Connections

Covers thermistor inputs via J1 and status switch inputs via J2.

Configuration and Options Setup

Explains DIP switches and configuration headers for unit setup.

Unit Operation and Control Modes

Demand Limit Control Strategies

Methods to limit unit capacity based on demand, including single-step and DLCM.

Digital Display and Operating Information

Codes and status shown on the unit's digital display during operation.

Unit Operating Sequences

Step-by-step functional logic of the VAV unit during various modes.

Specialized Control Modes

Building pressurization, smoke purge, and static pressure control options.

Service and Troubleshooting Procedures

Quick Test Program Execution

Procedure for checking system operational status and component functionality.

Component Locations and Adjustments

Physical locations of key components and DP switch adjustments.

Diagnostic Codes and Failure Analysis

Interpreting error codes, overload conditions, and probable causes.

Troubleshooting Specific Component Failures

Addressing potentiometer, thermistor, switch, and board failures.

Electronic Controls Checkout

Processor Board Testing Procedures

Steps to test the processor board's voltage and connections.

Relay Board Output Verification

Verifying relay board output signals and resistance readings.

Display, Accessory, and DLCM Board Checks

Testing display, accessory boards and demand limit control modules.

Thermistor and Wiring Diagnostics

Troubleshooting thermistors and reviewing control wiring diagrams.

Carrier 50DK030 Specifications