Bosch LV042 User Manual

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Installation and Maintenance Manual

LV MODEL

8733944336 (2016/09)

Table of Contents

Questions and Answers:

Z
Zachary ShafferAug 22, 2025
Why is my Bosch LV042 Heat Pump not shifting into cooling?
- A
  Andrew BellAug 22, 2025
  If your Bosch Heat Pump isn't shifting into cooling mode, check that the reversing valve solenoid is receiving 24 VAC. If it is, check the resistance of the solenoid; an open circuit may indicate a burned out solenoid. Also, check that the reversing valve thermostat wire is connected to the 'O' terminal of the thermostat and check for a contact closure between 'O' and 'R'. Finally, check that the wires from the thermostat to the unit are securely connected and that the wires from the electrical box to the reversing valve are connected.
M
michaelwilliamsAug 23, 2025
How to reduce objectionable noise levels from my Bosch LV042 Heat Pump?
- A
  Allen LewisAug 23, 2025
  If you're experiencing objectionable noise levels from your Bosch Heat Pump, ensure the duct work and grilles are properly sized for unit air flow. If the fan speed setting is too high, consult the blower performance table and reduce fan speed if possible. To address structure borne noise, mount the unit on a vibration pad. Also, install the unit in accordance with the provided instructions and adjust the unit location to prevent it from touching the structure.
D
Donald RodriguezAug 25, 2025
What to do if my Bosch Heat Pump compressor isn't running and the fan is on, but I suspect low refrigerant?
- J
  James BarnesAug 26, 2025
  If your Bosch Heat Pump's compressor isn't running but the fan is, it could be due to a low-pressure fault caused by low refrigerant. Check the refrigerant pressure with a gauge set.
J
jesusmartinAug 27, 2025
What to do if the compressor of my Bosch Heat Pump doesn't work but the fan runs and there is a freeze fault?
- L
  laura21Aug 27, 2025
  If your Bosch Heat Pump's compressor isn't running but the fan is, it could be due to a freeze fault in the water coil caused by no or low water flow. Check the water valves and/or pumps to ensure they are operating correctly. Also, check the water coil for any blockages.
J
Joshua ThompsonAug 27, 2025
Why is my Bosch Heat Pump compressor not running but the fan is, possibly due to high water temperature?
- K
  Kayla WalkerAug 27, 2025
  If your Bosch Heat Pump's compressor isn't running but the fan is, it could be due to a high-pressure fault caused by high water temperature. Check the water temperature to ensure it is within the appropriate range.
J
Joseph Smith DDSAug 29, 2025
How to troubleshoot a Bosch Heat Pump with no compressor operation but running fan, possibly due to a fouled water coil?
- M
  Michelle BowersAug 29, 2025
  If your Bosch Heat Pump's compressor isn't running but the fan is, it could be due to a high-pressure fault caused by a fouled or scaled water coil. Check for proper flow rate and water temperature, especially looking for a low water side temperature rise during cooling.
J
Jacqueline ShafferAug 30, 2025
What to do if my Bosch LV042 compressor isn't running but the fan is, and I suspect airflow issues?
- B
  Brenda NguyenAug 30, 2025
  If your Bosch Heat Pump's compressor isn't running but the fan is, it could be due to a high-pressure fault caused by no or low airflow. Check the fan motor to ensure it is operating correctly.
D
David HallAug 31, 2025
Why is my Bosch LV042 Heat Pump compressor not running but the fan is, possibly due to low airflow?
- S
  Seth PerkinsAug 31, 2025
  If your Bosch Heat Pump's compressor isn't running but the fan is, it could be due to a low-pressure fault caused by no or low airflow. Check the fan motor to ensure it is operating correctly.
S
Steven ClarkSep 2, 2025
What to do if my Bosch Heat Pump compressor isn't running but the fan is on and I suspect an overloaded control circuit?
- B
  brianjonesSep 2, 2025
  If the compressor of your Bosch Heat Pump is not working, but the fan is running, it might be due to a brown-out fault caused by an overloaded control circuit. Check the control voltage; if it's below 18V, inspect the accessories connected to the unit and ensure they don't exceed the VA draw.
L
Lacey HernandezSep 3, 2025
How to troubleshoot a Bosch LV042 Heat Pump with no compressor operation but running fan, possibly due to a bad thermostat connection?
- L
  Lisa OrrSep 3, 2025
  If the compressor of your Bosch Heat Pump is not working, but the fan is running, it might be due to a brown-out fault caused by a bad thermostat connection. Check that the thermostat wiring is of the proper gauge and length, is undamaged, and that all connections at the thermostat and heat pump are secure.

Bosch LV042 Specifications

General

Brand	Bosch
Model	LV042
Category	Heat Pump
Language	English

Summary

Key Symbols and Safety Warnings

Key Symbols

Explains symbols used in the manual for warnings and important information.

Safety Warnings

Outlines critical safety precautions for installation, service, and operation.

General Description and Unit Handling

Installation Preparation

Initial steps for installation, including job site checks and unit inspection.

Unit Mounting and Ducting

Step 4: Mount the Unit

Methods for mounting vertical and horizontal units, including pad usage and pitching.

Duct System and Drain Installation

Step 6: Install Condensate Drain

Proper installation of the condensate drain line, including trap and vent requirements.

Piping and Electrical Connections

Step 8: Wire Field Power Supply

High voltage power wiring requirements, code compliance, and transformer settings.

Low Voltage Wiring and Thermostat Integration

Unit Controls and Safety Devices

Step 9: Wire Field Controls

Wiring field controls, including ECM interface board and UPM control connections.

ECM Interface Board and UPM Control

ECM interface board functions and UPM control board features and indicators.

UPM Board Features and Safety Devices

Safety Features Overview

Key safety features like high/low pressure switches and freeze protection sensors.

UPM Board Functionality

Features like anti-short cycle timer, random start, low pressure bypass, and malfunction output.

Freeze Protection and Reset Procedures

Freeze Sensor Operation

Freeze sensor settings and operation for water and air coils to prevent freezing.

Intelligent Reset and Lockout Reset

Pre-Start-Up Checks and Operating Limits

Pre-Start-Up System Checkout

Essential system checks before initial unit startup and energizing.

Start-Up Procedure

Steps to initiate a proper start-up sequence for cooling and heating cycles.

Compressor Operation and Start-Up

Scroll Compressor Rotation

Unit Start-Up Procedures

Unit Start Up Cooling Mode

Steps to verify proper operation during the cooling cycle.

Unit Start Up Heating Mode

Steps to verify proper operation during the heating cycle.

Fan Motor Options

Permanent Split Capacitor Motors (PSC)

Constant Airflow Motors (ECM)

Constant Airflow Motors (ECM) Features

Unit Troubleshooting Guide

No Compressor Operation but Fan Runs

Troubleshooting for fan running but no compressor operation with fault LED codes.

Freeze Faults

Troubleshooting steps for freeze faults related to water coils and refrigerant.

Troubleshooting Common Faults

Condensate and Brown Out Faults

Troubleshooting for condensate overflow and brown-out faults with various causes.

Thermostat and Airflow Related Faults

Issues related to thermostat connections, air coil faults, and blocked return air.

Troubleshooting Compressor and Fan Issues

Compressor Operation Issues

Troubleshooting for open compressor overload, wiring, and burned-out compressors.

Fan Operation Issues (PSC Motor)

Troubleshooting for PSC motor fan operation, including relay and motor issues.

Fan Operation Issues (Constant Torque Motor)

Troubleshooting for constant torque motor fan operation, wiring, and interface board.

Troubleshooting Airflow and Cooling/Heating Issues

Constant Airflow Motor and Unit Shifting Issues

Troubleshooting for constant airflow motors and unit mode shifting problems.

Air Temperature and System Performance Issues

Troubleshooting for incorrect supply air temperatures and system performance loss.

Troubleshooting Humidity and Noise Issues

High Humidity and Unit Oversizing

Objectionable Noise Levels

Temperature and Pressure Operating Data

Table 13: Operating Data

Wiring Diagrams

UPM Status LED Blink Codes

Meaning of different blink codes displayed by the UPM status LED.

Maintenance and Decommissioning

Routine Maintenance

Required maintenance tasks such as filter changes and annual check-ups.

Information on Decommissioning

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