Bosch EP048 User Manual

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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:

J
Jeffrey MitchellAug 16, 2025
What to do if my Bosch EP048 Heat Pump is off on high pressure control?
- G
  greenemeganAug 16, 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.
A
Amy LucasAug 21, 2025
Why is the blower operating but the compressor not in my Bosch EP048?
- S
  sara99Aug 21, 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.
O
Olivia ClarkAug 27, 2025
What causes a Bosch EP048 to turn off on low pressure control?
- M
  Melanie MoonAug 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.
S
Stanley FlemingSep 1, 2025
Why does my Bosch Heat Pump unit short cycle?
- B
  bushrobertSep 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.

Bosch EP048 Specifications

General

Brand	Bosch
Model	EP048
Category	Heat Pump
Language	English

Summary

Model Nomenclature

Initial Inspection and General Description

Condensate Drain and Duct System

Duct System

Piping and Electrical Installation

Electrical

Field wiring must comply with codes. Power must match unit voltage range.

Thermostat Connections and ECM Interface Board

Thermostat Terminal Functions and LED Indicators

Safety Devices and UPM Controller

UPM Board Settings and DIP Switch Configuration

UPM DIP Switch Configuration

Details factory default settings and DIP switch positions for the UPM board.

Electronic Thermostat Installation and Wiring

UPM Sequence of Operation

Electric Heater Package Option and Water Quality

Water Quality

Importance of maintaining proper water quality for heat pump longevity and performance.

Water Quality Table

Heat Recovery Package and HRP Water Piping

Water Tank Refill, Initial Start-Up, and Hot Gas Reheat

Sequence of Operation and Well Water Systems

Geothermal (Earth-Coupled) Systems

System Checkout and Unit Start-Up

Unit Start-Up

Step-by-step guide for initial unit start-up and verification.

Maintenance and Filter Changes

Filter Changes and Cleaning

Guidelines for regular filter changes and cleaning based on environment.

Unit Check-Out Sheet

Troubleshooting and UPM Board LED Indications

UPM Board LED Indications

Unit Troubleshooting

Unit Off On High Pressure Control

Diagnosing and correcting issues when the unit is off due to high pressure.

HRP Troubleshooting

Refrigerant Pressure Ranges

Wiring Diagrams and UPM Status LED Blink Codes

UPM Status LED Blink Codes

Explanation of UPM board LED blink codes for fault identification.

Wiring Diagrams with Component Legends

Wiring Diagrams with ECM and Heater Connections

Electric Heat Elements and Wiring

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