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Bosch EP042 - User Manual

Bosch EP042
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Installation and Maintenance Manual
EP Series
8733953041 (2019/01)
EP007, EP009, EP012, EP015, EP018, EP024, EP030, EP036, EP042, EP048, EP060,EP070

Table of Contents

Questions and Answers

  • D
    davidleonardAug 17, 2025
    What to do if my Bosch Heat Pump is off on high pressure control?
    • M
      Matthew AllenAug 17, 2025
      If your Bosch Heat Pump shuts off due to high pressure, it could be due to several reasons. In cooling mode, check for inadequate water flow, excessively warm entering water temperature, or a scaled or plugged condenser. In heating mode, ensure adequate airflow by checking for an inoperative blower, clogged filter, or restrictions in the ductwork. Also, the unit might be overcharged with refrigerant, so reclaim the excess, evacuate, and recharge it with the factory-recommended amount. Finally, inspect the high-pressure switch for defects or improper calibration.
  • T
    thomas04Aug 22, 2025
    Why is the blower operating but the compressor not in my Bosch EP042?
    • K
      Kathryn HarrisAug 22, 2025
      If your Bosch Heat Pump's blower is running but the compressor isn't, check the thermostat settings, calibration, and wiring. Inspect for loose or broken wires at the compressor, capacitor, or contactor. Check the UPM board's red default LED for a Blink Code. If the compressor is cool and the overload won't reset, it may need replacement. A compressor motor grounded internally to the shell also necessitates replacement. After the compressor cools, check the continuity of its windings; open windings indicate the need for a replacement.
  • A
    Andrew RiveraAug 27, 2025
    What causes a Bosch EP042 Heat Pump to turn off on low pressure control?
    • A
      Ann RussoAug 27, 2025
      If your Bosch Heat Pump is turning off due to low pressure, the suction pressure might be too low. In cooling mode, this could be due to inadequate airflow, excessively cold entering air temperature, an inoperative blower, a clogged filter, or ductwork restrictions. In heating mode, it could be due to inadequate water flow, excessively cold entering water temperature, or a scaled or plugged condenser. Also, the unit might be low on refrigerant, so check for leaks, repair them, evacuate the system, and recharge it with the factory-recommended amount. Finally, inspect the low-pressure switch for defects or improper calibration.
  • J
    Jennifer DixonSep 1, 2025
    Why does my Bosch EP042 Heat Pump unit short cycle?
    • J
      Jasmine MorganSep 1, 2025
      If your Bosch Heat Pump is short cycling, it might be oversized for the space, so recalculate the heating and cooling loads. The thermostat could be installed near a supply air grill; if so, relocate it and readjust the heat anticipator. Also, check the wiring and controls for a defective or improperly calibrated low-pressure switch.
  • N
    Natalie MatthewsNov 6, 2025
    How to troubleshoot a Bosch EP042 that does not run?
    • E
      Elizabeth CollinsNov 6, 2025
      If your entire Bosch Heat Pump unit isn't running, start by ensuring the power supply is on and the disconnect is closed. Check for blown fuses and replace them or reset the circuit breaker, making sure you're using the correct fuses. If the voltage supply is lower than the minimum specified on the unit's data plate, contact your local power company. Also, check the thermostat settings, calibration, and wiring. Set the fan to “ON”—it should run. Set the thermostat to “COOL” at the lowest temperature; the unit should cool. Set it to “HEAT” at the highest temperature; the unit should heat. If the blower or compressor doesn't run in any of these cases, the thermostat might be miswired or faulty. Verify 24 volts at the low voltage terminal strip between “R” and “C”, “Y” and “C”, and “O” and “C...
  • K
    Kristy MurphyNov 11, 2025
    Why is my Bosch EP042 providing insufficient cooling or heating?
    • M
      mayerchristianNov 11, 2025
      If your Bosch Heat Pump isn't providing enough cooling or heating, several factors could be at play. First, the unit might be undersized, so recalculate the heating or cooling loads. Adding insulation and shading might help. Check for air leaks in the ductwork or from outside through doors and windows. Ensure adequate airflow and proper air distribution, and replace any dirty filters. A low refrigerant charge can cause inefficient operation, so check the refrigerant levels. Inspect the compressor for defects; low discharge and high suction pressure indicate it's not pumping correctly, so replace it if needed. A defective reversing valve can also cause problems by bypassing refrigerant, so consider replacing it. Compare operating pressures to the unit's pressure/temperature chart. Check the...

Summary

Model Nomenclature

Initial Inspection

Safety Precautions

Warnings and cautions for installation, servicing, and operation.

Hanging Bracket Kit

Condensate Drain

Piping

ECM Interface Board

Thermostat Terminal Functions

Thermostat Control Features

Safety Devices and UPM Controller

Safety Control Features

Details on safety controls like freeze protection and overflow sensors.

UPM Board Settings and Features

UPM DIP Switch Settings

Default positions for UPM DIP switches and their functions.

UPM Board Features

Explanation of UPM features like timers, lockout, and protection.

Electronic Thermostat Installation

LED Fault Indication

Thermostat Wiring Diagram

UPM Sequence of Operation

Electric Heater Package Option

Water Quality Table

Heat Recovery Package (HRP)

Sequence of Operation

Cooling Mode

Heating Mode

Geothermal (Earth-Coupled) Systems

System Checkout

Unit Start-Up

Maintenance

Filter Changes and Cleaning

Guidelines for filter maintenance based on environment.

Annual Checkup

Lubrication and Drain Checks

Periodic Lockouts

Troubleshooting

UPM Board LED Indications

Table explaining UPM board LED blink codes and meanings.

Unit Troubleshooting (General)

Common problems, causes, and checks for unit operation.

Unit Troubleshooting (High;Low Pressure)

Unit Troubleshooting (Cycles & Insufficient Cooling;Heating)

HRP Troubleshooting

No Flow; Low Flow

Troubleshooting steps for no or low flow issues with HRP.

High Water Temperature; Low Heat Output

Troubleshooting for high water temperature and low heat output.

Refrigerant Pressure Ranges

Wiring Diagrams

UPM Status LED Blink Codes

Explanation of UPM board LED blink codes.

Standard Components Legend

Wiring Diagrams (General Unit)

Wiring Diagrams (Hot Gas Reheat)

Wiring Diagrams (Motor Selection)

Wiring Diagrams (Heat Recovery)

Electric Heat Wiring Diagrams

Bosch EP042 Specifications

General IconGeneral
BrandBosch
ModelEP042
CategoryHeat Pump
LanguageEnglish

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