Lennox ML193UH070XE36B

Page 1
© 2019 Lennox Industries Inc.
Litho U.S.A.
Corp. 1905
ML193UHE
Service Literature
ML193UHE SERIES UNITS
ML193UHE series units are high-efficiency gas fur
naces manufactured with Lennox DuralokPlust alumi
nized steel clamshell-type heat exchangers, with a stainless
steel condensing coil. ML193UHE units are available in
heating input capacities of 30,000 to 110,000 Btuh (8.8 to
32.2 kW) and cooling applications from 2 through 5 tons (7.0
through 17.6 kW). Refer to Engineering Handbook for proper
sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LPG operation. All ML193UHE
units are equipped with a hot surface ignition system. The
gas valve is redundant to assure safety shut-off as re
quired by C.S.A.
The heat exchanger, burners and manifold assembly can be
removed for inspection and service. The maintenance section
gives a detailed description on how this is done.
The ML193UHE can be “twinned” with a second unit. See
twinning kit 16W72 for information for two units to operate
as one, in a shared duct system controlled by a single ther
mostat.
All specifications are subject to change. Procedures outlined
in this manual are presented as a recommendation only
and do not supersede or replace local or state codes.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon
nect switch(es). Unit may have multiple
power supplies.
Table of Contents
Specifications 2.................................
Optional Accessories 4..........................
Blower Performance Data 5......................
I-Unit Components 7............................
II Placement and Installation 20....................
III-Start-Up 39...................................
IV-Heating System Service Checks 40..............
V-Typical Operating Conditions 44.................
VI-Maintenance 45...............................
VII-Sequence of Operation and Flow Charts 48......
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller (or equivalent), service agency or the gas sup
plier.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.

Lennox ML193UH070XE36B Specifications

General

Model	ML193UH070XE36B
Type	Gas Furnace
Efficiency Rating	93% AFUE
Ignition Type	Direct Spark Ignition
Stages	Single Stage
Fuel Type	Natural Gas
Input BTU	70, 000 BTU
AFUE Rating	93%
Blower Motor Type	ECM
Warranty	10-Year Limited Warranty

Summary

ML193 UHE Series Unit Information

WARNING: Electric Shock Hazard

Electric shock hazard warning before performing service or maintenance.

WARNING: Improper Installation and Service

Warning about potential damage or injury from improper installation, adjustment, or service.

CAUTION: Sharp Sheet Metal Edges

Blower Performance Data

ML193 UH030 XE36 B Blower Performance

ML193 UH045 XE36 B Blower Performance

ML193 UH070 XE36 B Blower Performance

ML193 UH090 XE36 C Blower Performance

Blower Performance Data (Continued)

ML193 UH090 XE48 C Blower Performance

ML193 UH110 XE48 C Blower Performance

ML193 UH110 XE60 C Blower Performance

ML193 UHE Parts Identification

FIGURE 1: Exploded View of Components

Exploded view of the furnace highlighting major components.

I-UNIT COMPONENTS

Electrostatic Discharge (ESD) Precautions

Procedures to prevent damage from static discharge to electronic components.

Integrated Ignition Control (A92)

Integrated Control and Ignition System

Electronic Ignition Sequence Explanation

Detailed explanation of the electronic ignition sequence and safety checks.

Heating Compartment Components

ML193 UHE Burner Box Assembly Diagram

Diagram showing components within the burner box assembly.

B-Heating Components Overview

1. Flame Rollout Switches (Figure 5)

2. Heat Exchanger (Figure 6)

Heat Exchanger and Gas Valve Details

Primary Limit Location and Heat Exchanger (Figure 6)

4. Gas Valve (Figure 7) Operation

5. Flame Sensor Function and Measurement

To Measure Flame Signal - Integrated Control

Procedure for measuring flame signal using a microamp DC meter.

Flame Signal and Ignitor Testing

Measuring Flame Signal Procedure

Procedure and diagram for measuring flame signal.

FIGURE 8: Flame Signal Measurement Setup

Illustration of flame signal measurement setup.

Ignitor Testing Procedures

Test 1: Ignitor Circuit Resistance Check

Test 2: Ignitor Resistance at Plug Check

Test 3: Ignitor Voltage Check Procedure

FIGURE 9: Ignitor Test Diagrams

Combustion Air System Components

7. Combustion Air Inducer & Cold End Header Box

8. Combustion Air Pressure Switch (Figure 10)

Pressure Differential Measurement

Measuring Pressure Differential Procedure

Procedure and diagram for measuring pressure differential.

FIGURE 11: Pressure Differential Measurement Setup

Illustration of pressure differential measurement setup.

Pressure Switch Troubleshooting Guide

TABLE 7: Pressure Switch Troubleshooting Guide

Comprehensive troubleshooting guide for pressure switch issues.

Blower Compartment and Secondary Limit

C- Blower Compartment Overview

9. Secondary Limit Controls Function

Motor Module Replacement and Installation

Motor Module Replacement Procedure

Step-by-step guide for replacing the motor module.

Motor Testing Procedures (Resistance & Spin)

Motor Module Installation Guidelines

Instructions for installing a new motor control module.

FIGURE 19: Drip Loop for Electrical Connectors

Joint Cementing Procedure and Terminations

Joint Cementing Procedure Steps

DANGER: Explosion Hazard from PVC Fumes

Danger warning about PVC glue fumes igniting during system check.

Venting Practices and Guidelines

CAUTION: Exhaust Vent Pressure and Sealing

Caution regarding positive pressure in exhaust vent pipe requiring sealed joints.

Vent Pipe Sizing and Minimum Lengths

Piping Size Process Steps

IMPORTANT: Avoid Screens in Terminations

Important note against using screens in terminations to prevent freeze-ups.

Maximum Vent Pipe Lengths

TABLE 12: Max IntakeExhaust Vent Lengths

TABLE 13: Max Exhaust Vent Lengths (ClosetBasement)

Typical Exhaust and Intake Pipe Connections

FIGURE 24: Upflow Vent Pipe Connections

FIGURE 25: Horizontal Vent Pipe Connections

Confined Space Installation and Venting

CAUTION: Combustion Air in Confined Spaces

Caution regarding negative pressure affecting combustion air intake sizing.

Maximum Uninsulated Vent Pipe Lengths

TABLE 14: Uninsulated Vent Lengths by Temperature

VENT TERMINATION CLEARANCES - NON-DIRECT VENT

FIGURE 31: Non-Direct Vent Termination Clearances

Diagram showing non-direct vent termination clearances.

VENT TERMINATION CLEARANCES - DIRECT VENT

FIGURE 32: Direct Vent Termination Clearances

Diagram showing direct vent termination clearances.

Condensate Trap and Drain Assembly Details

FIGURE 44: Condensate Trap and Plug Locations

CAUTION: Avoid Copper Tubing for Condensate Lines

Caution against using copper tubing for condensate lines.

Evaporator Coil Condensate Management

FIGURE 46: Remote Condensate Trap Locations

FIGURE 48: Condensate Trap with Overflow Switch

ML193 UHE with Evaporator Coil - Separate Drain

Evaporator Coil Drain Configurations

FIGURE 49 & 51: Horizontal Coil Drain Configurations

FIGURE 50: Common Drain for Coil and Furnace

IMPORTANT: Venting Combined Drains

Important note on venting combined drains for proper pressure switch operation.

TRAP DRAIN ASSEMBLY USING PVC

FIGURE 52: PVC TrapDrain Assembly Diagrams

Illustrations of trap/drain assemblies with 1/2" and 3/4" PVC piping.

III-START-UP PROCEDURES

Heating Start-Up Sequence

Priming the Condensate Trap

WARNING: Fire or Explosion Hazard

Critical warning about fire or explosion hazards if instructions are not followed.

Gas Valve Operation and Safety (Figure 53)

Instructions for operating the gas valve and safety precautions.

Troubleshooting Unit Failure to Operate

Checklist for troubleshooting unit failure to operate.

IV-HEATING SYSTEM SERVICE CHECKS

Testing Gas Supply Pressure and Flow

Procedures for testing gas supply pressure and flow.

TABLE 16: Gas Meter Clocking Chart

Gas meter clocking chart for determining gas flow rates.

Manifold Pressure Measurement Procedure

Steps for measuring manifold pressure using a manometer.

Manifold Pressure Measurement Setup

FIGURE 55: Manifold Pressure Measurement Diagram

Diagram illustrating manifold pressure measurement setup.

Combustion Analysis and High Altitude Installation

E-Proper Combustion Analysis Procedure

Procedure for checking combustion by measuring CO2 and CO levels.

TABLE 17: CO2% for Natural Gas and LP

Table of CO2% for Natural Gas and LP.

Ground and Voltage Checks for Control System

G- Proper Ground and Voltage Verification

Procedure for checking furnace ground and voltage to the integrated control.

WARNING: Electrical Shock Hazard and Grounding

Warning about electrical shock hazard and proper grounding.

FIGURE 56: Control Voltage Check Diagrams

Diagrams showing voltage checks on the integrated control.

TABLE 20: Expected vs. Maximum VAC Readings

Table of expected and maximum VAC readings for furnace status.

VI-MAINTENANCE PROCEDURES

WARNING: General Safety Precautions for Servicing

Broad safety warning for servicing, including electrical hazards.

Winterizing and Condensate Trap Care

Condensate Hose Screens Maintenance (Figure 59)

Heat Exchanger Cleaning Procedure

Heat Exchanger Cleaning Steps

Detailed procedures for cleaning the heat exchanger assembly.

FIGURE 59: Condensate Hose Screen Illustration

Cleaning the Burner Assembly

Burner Assembly Cleaning Steps

Step-by-step instructions for cleaning the burner assembly.

VII-WIRING DIAGRAM AND SEQUENCE OF OPERATION

Furnace Wiring Diagrams

Heating Sequence of Operation Explanation

Troubleshooting: Heating Sequence of Operation

Heating Sequence Flow Chart

Visual guide to diagnose heating sequence issues using LED flash codes.

Heating Sequence Troubleshooting (Continued)

Heating Sequence Flow Chart Continuation

Continuation of the heating sequence troubleshooting flowchart.

Troubleshooting: Cooling Sequence of Operation

Cooling Sequence Flow Chart

Flowchart for troubleshooting the cooling sequence of operation.

Troubleshooting: Continuous Fan Accessories Sequence

Continuous Fan Sequence Flow Chart

Flowchart for troubleshooting continuous fan and accessory operation.