Lennox 16B27 - User Manual

This document describes the Lennox Air Handler Control Field Replacement Kit (16B27), which supersedes kits 65W70 and 13Y22 and is backwards compatible. It provides guidelines for the field replacement and configuration of air handler controls, focusing on both communicating and non-communicating systems.

Function Description:

The Lennox Air Handler Control (AHC) is a crucial component for managing the operation of air handler units. It facilitates the control of various functions, including blower speed for both heating and cooling modes, electric heat staging, and dehumidification. The AHC can be configured for either communicating systems, typically using an iComfort® thermostat, or non-communicating systems, which rely on jumper and link settings on the control board itself.

For non-communicating systems, the AHC operates based on the physical jumper and link settings. These settings determine the unit's size code, blower speeds for different modes (cooling, heat, continuous fan), and delay profiles for blower ramping. The control board includes a single-character LED display and a push button for configuration and diagnostic purposes.

In communicating systems, the AHC integrates with iComfort® thermostats, where system configuration is primarily managed through the thermostat's installation instructions. The jumper and link settings on the AHC serve as default settings and only govern system operation if the iComfort® thermostat's configuration settings are unavailable.

The AHC is designed to detect and manage electric heat stages. It can automatically identify the number of field-installed electric heat sections by sensing current through external relay coils. This information is crucial for proper operation, especially in EvenHeat mode.

Usage Features:

The AHC offers several features for controlling and monitoring air handler operation:

Blower Speed Control: Users can select different blower speeds for cooling and heating modes (High, Medium-High, Medium-Low, Low) using jumpers. There are also options for continuous fan blower speed. The "ADJUST" jumper allows for fine-tuning CFM by selecting normal, +10%, or -10% of the normal speed.
Delay Profiles: The AHC incorporates delay profiles for blower ramping during cooling and heat pump operations. These profiles dictate how the motor ramps up and down, with options like immediate ramp-up to 100% (Delay Profile 1) or more gradual ramping with intermediate speeds (Delay Profiles 2, 3, and 4). For heat pump operation, only Delay Profiles 1 and 2 are applicable; if 3 or 4 are selected, the control defaults to Profile 1.
Humidification Control: The AHC manages the status of the H terminal on the thermostat block. Depending on the jumper setting (SMART or AUTO), the H terminal can be active when heat demand is present and the indoor blower is running (SMART), or energized whenever the indoor blower is running (AUTO).
EvenHeat Operation: This mode allows for setting target discharge air temperatures (85°F, 100°F, 115°F/130°F) for enhanced heating performance. An optional Discharge Air Temperature Sensor (DATS) is required for EvenHeat operation.
Single-Character LED Display: This display provides real-time status information, including the unit size code, active cooling/heating stages, dehumidification mode, defrost mode, indoor blower CFM, and discharge air sensor temperature.
Push Button for Configuration and Diagnostics: A push button on the control board allows users to cycle through different operation modes, recall stored error codes, configure electric heat sections, perform an indoor blower test, and set unit size codes.
Error Code Recall: The AHC stores up to ten diagnostic error codes, which can be recalled using the push button. These codes help in troubleshooting various issues, such as device communication problems, low voltage, unresponsive devices, configuration jumper errors, indoor blower failures, and electric heat section failures.
Target CFM Tables: The manual provides detailed tables for different air handler models (CBX32MV, CBX40UHV, CBA38MV) that list the expected CFM values for various jumper speed positions in both "HEAT" and "COOL" modes, considering external static pressure ranges.

Maintenance Features:

Troubleshooting with Error Codes: The comprehensive list of error codes (E105 to E420) and their descriptions aids in quickly identifying and diagnosing operational issues. This allows technicians to pinpoint problems related to communication, power, sensors, blower motor, and electric heat.
Configuration Procedures: The document outlines clear procedures for configuring the unit, including setting the unit size code and detecting electric heat sections. These steps are essential after replacing the control board to ensure proper functionality.
Electrostatic Discharge (ESD) Precautions: A dedicated warning emphasizes the importance of ESD precautions during installation and service to protect electronic components. This includes touching an unpainted unit surface to neutralize static charge before handling the controls.
Safety Warnings: The manual includes critical warnings regarding electric shock hazards, proper grounding, and the dangers of sharp sheet metal edges, guiding technicians to perform maintenance safely.
Wiring Diagrams: A typical wiring diagram (Form No. 537202-02) is provided for CBA38MV, CBX32, and CBX40 Air Handler Units, which is invaluable for correct wiring and troubleshooting.
Component Connections: Detailed information on component connections, including the Indoor Blower Signal 6-Pin Connector (P7) and Air Handler Control 9-Pin Connector (P8), helps ensure all wires are correctly connected.
Field Replacement Guidelines: The document serves as a guide for replacing the air handler control, including steps for disconnecting power, removing access panels, transferring wire connections, and securing the new control.