Lennox SCH120 User Manual

©2019
SGH120 SHOWN
IMPORTANT
Supply air VFD motor rotation is controlled indepen
dently from scroll compressor rotation. See Cooling
Start-Up section for correct compressor rotation.
Compressor damage due to improper rotation is the
responsibility of the installer.
Table of Contents
Dimensions Page 2.................................
Parts Arrangements Page 5.........................
Shipping and Packing List Page 8....................
General Page 8....................................
Safety Page 8.....................................
Unit Support Page 9................................
Duct Connection Page 10............................
Rigging Unit For Lifting Page 10.......................
Condensate Drains Page 10..........................
Gas Piping Page 11.................................
Pressure Test Gas Piping Page 11.....................
RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE
INSTALLATION
INSTRUCTIONS
SGH/SCH036 (3 TON)
SGH/SCH060 (5 TON)
SGH/SCH120 (10 TON)
SGH/SCH240 (20 TON)
ROOFTOP UNITS
507964-01
9/2019
Supersedes 507364-02
High Altitude Derate Page 12.........................
Optional Outdoor Air Hood Page 13....................
Electrical Connections Page 15.......................
Blower Operation and Adjustments Page 17............
Cooling Start-Up Page 29............................
Cooling Operation and Adjustments Page 31............
Gas Heat Start-Up Page 41...........................
Electric Heat Start-Up Page 43........................
Heating Operation and Adjustments Page 43............
MSAV
t Unit Start-Up Page 45........................
MSAV
t Operation Page 46..........................
Direct Drive Start-Up Page 47.........................
Hot Gas Reheat Startup Page 49......................
Economizer Start-Up Page 53.........................
Service Page 55....................................
Factory Control Parameter Settings Page 58............
Start-Up Report Page 60.............................
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
WHAT TO DO IF YOU SMELL GAS:
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury or loss of life.
WARNING
Do not store or use gasoline or
other flammable vapors and liq
uids in the vicinity of this or any
other appliance.
Installation and service must be
performed by a qualified installer,
service agency or the gas supplier.
S Do not try to light any appliance.
S Extinguish any open flame.
S Do not touch any electrical switch; do not
use any phone in your building.
S Immediately call your gas supplier from a
neighbor's phone. Follow the gas suppli
er's instructions.
S If you cannot reach your gas supplier, call
the fire department.
S Leave the building immediately.

Lennox SCH120 Specifications

General

Brand	Lennox
Model	SCH120
Category	Air Conditioner
Language	English

Summary

Installation Instructions

Important Installation Notes

Key operational and safety guidelines for unit installation.

Safety Warnings and Procedures

Critical warnings and gas leak emergency steps.

SG/SC 036 & 060 Dimensions

SG/SC 120 Dimensions

SG/SC 240 Dimensions

Shipping and Packing Information

Installation Safety Precautions

Warnings regarding electrical shock and refrigerant.

Gas Piping Connection and Testing

Electrical Connections

Power Supply Wiring

Instructions for connecting the main power supply to the unit.

Control Wiring and Thermostats

Guidelines for wiring thermostats and zone sensors.

Thermostat and Zone Sensor Placement

Field Wiring Diagrams

Electronic & Electro-Mechanical Thermostat Wiring

Zone Sensor Mode Wiring

Blower Operation and Adjustments

Blower Control Methods

How blower rotation is controlled on VFD and belt-driven units.

Blower Start-Up Operation

Static Pressure Readings

Determining Unit CFM

CFM Calculation for Wet Coils

Procedure for calculating CFM for wet coils with VFD blowers.

Adjusting Belt Tension

Checking Belt Tension

Blower Data SGH036H/SGH060H

Blower Data SGH120HM

Blower Data SGH240HM

Blower Data SCH036H / SCH060H

Blower Data SCH120HM

Blower Data SCH240HM

Cooling Start-Up Procedures

Critical Start-Up Warnings

Electrical shock and crankcase heater warnings.

Power and Phase Detection

How the Unit Controller handles incorrect power phase.

Pre-Start-Up Checks

Refrigerant Circuits Diagrams

Cooling Operation and Adjustments

Refrigerant Charge and Check Procedure

Procedure for checking and adjusting refrigerant charge.

SG/SC 036 Operating Pressures

SG/SC 036 Operating Pressures with Reheat

Operating Pressures Tables

SG/SC 060 Operating Pressures (No Reheat)

SG/SC 060 Operating Pressures (Reheat)

SG/SC 120 Operating Pressures

SG/SC 240 Operating Pressures (No Reheat)

SG/SC 240 Operating Pressures (Reheat)

SG/SC 240 Normal Operating Pressures - Reheat

SG/SC 036 Charging Curves (No Reheat)

SG/SC 036 charging curves for no reheat operation.

Cooling Charging Curves

SG/SC 036 Charging Curves (Reheat)

SG/SC 036 charging curves for reheat operation.

SG/SC 060 Charging Curves (No Reheat)

SG/SC 060 charging curves for no reheat operation.

SG/SC 060 Charging Curves (Reheat)

SG/SC 120 Refrigerant Circuit Curves

Circuit 1 SG/SC 120 Curves

Charging curves for Circuit 1 of SG/SC 120 units.

Circuit 2 SG/SC 120 Curves

Charging curves for Circuit 2 of SG/SC 120 units.

SG/SC 240 No Reheat Charging Curves

Circuit 1 SG/SC 240 Curves

Charging curves for Circuit 1 of SG/SC 240 units (No Reheat).

Circuit 3 SG/SC 240 Curves

Charging curves for Circuit 3 of SG/SC 240 units (No Reheat).

Circuit 2 SG/SC 240 Curves

Charging curves for Circuit 2 of SG/SC 240 units (No Reheat).

Circuit 4 SG/SC 240 Curves

Charging curves for Circuit 4 of SG/SC 240 units (No Reheat).

SG/SC 240 Reheat Charging Curves

Circuit 1 SG/SC 240 Reheat Curves

Charging curves for Circuit 1 of SG/SC 240 units (Reheat).

Circuit 3 SG/SC 240 Reheat Curves

Charging curves for Circuit 3 of SG/SC 240 units (Reheat).

Circuit 2 SG/SC 240 Reheat Curves

Charging curves for Circuit 2 of SG/SC 240 units (Reheat).

Circuit 4 SG/SC 240 Reheat Curves

Charging curves for Circuit 4 of SG/SC 240 units (Reheat).

Compressor Controls

Compressor Oil Heater Function

Function and energization of the compressor oil heater.

Low Ambient Fan Control Logic

How low ambient switches control condenser fans.

Outdoor Fan Relay Operation

Low Ambient Fan Cycling Behavior

Unit Operation and Gas Safety

Placing Unit In Operation

Procedure for safely placing the unit into operation.

Gas Valve Operation

Step-by-step procedure for operating the gas valve.

Turning Off Gas to Furnace

Procedure for safely shutting off gas supply.

Heating Operation and Adjustments

Gas Heating Sequence of Operation

Step-by-step sequence for gas heating operation.

Gas Manifold Pressure Adjustment

Proper Gas Flow Measurement

Gas Meter Clocking Chart

MSAV™ Unit Start-Up

Setting Blower CFM Design Specifications

Adjusting Blower Pulley for Maximum CFM

Entering Blower CFM into Controller

MSAV™ Operation

Two-Stage T'Stat Operation (2/4 Compressors)

Zone Sensor Operation (240 Units)

Direct Drive Blower Start-Up

Setting Blower Speed via Controller

Entering design specified blower CFM into the controller.

Setting Minimum Damper Positions

Hot Gas Reheat Start-Up and Operation

Reheat System Overview

Function of hot gas reheat for dehumidification.

Reheat Coil Solenoid Valve Control

Reheat Setpoint Adjustment

Humidity Sensor Functionality

Reheat Refrigerant Routing

Reheat Operation Check-Out

Default Reheat Operation Modes

Reheat Operation Table

Optional Economizer Settings

Economizer General Function

Purpose of the economizer for free cooling.

Economizer Configuration Steps

Steps to configure economizer options via the Unit Controller.

Economizer Operation Modes

Standard Two-Stage Thermostat Control

Damper Minimum Position Settings

IAQ Damper Control

Unit Service and Maintenance

Filter Checking and Replacement

Burner Inspection and Cleaning (SG Units)

Ignitor and Sensor Positioning

Combustion Air Inducer Operation

Combustion Air Inducer Cleaning

Flue Passageway and Flue Box Maintenance

Coil Inspection and Cleaning

Factory Unit Controller Settings

BACnet Module Configuration

LonTalk Configuration

Room Sensor and Gateway Setup

Staged Blower CFM Settings

Start-Up Report Procedures

Initial Inspections and Checks

Checklist for initial unit inspections and electrical connections.

Cooling Performance Data Recording

Blower Performance Data Recording

Heating Performance Data Recording

Accessory Performance Data Recording