Bosch SM Split CS Series

Questions and Answers

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James YangAug 4, 2025
Why is my Bosch SM Split CS Heat Pump not cooling or heating enough?
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  Jessica VillaAug 4, 2025
  Insufficient cooling or heating in your Bosch Heat Pump can stem from several causes. The unit might be undersized, requiring recalculation of heating/cooling loads, possibly with added insulation. Leaks in ductwork or ambient air entering through doors/windows could cause loss of conditioned air. Inadequate airflow, often due to a dirty filter, can also be a factor. A low refrigerant charge leads to inefficient operation. Other potential issues include a defective compressor or reversing valve, restrictions or defects in the TXV, or contamination of the refrigerant system with moisture or non-condensables. Compare the unit's operating pressures to the pressure/temperature chart to diagnose the issue.
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tylerwilliamsAug 10, 2025
What to do if my Bosch SM Split CS Heat Pump is not running at all?
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  kathyclarkAug 10, 2025
  If your Bosch Heat Pump isn't running, start by checking the power supply. Ensure the disconnect is closed and power is applied. Inspect for blown fuses or tripped breakers, replacing or resetting them as necessary, ensuring correct fuse size. Verify the voltage supply meets the unit's data plate specifications; if it's low, contact your local power company. Also, examine the thermostat. Set the fan to 'ON' to see if the fan runs. Test 'COOL' and 'HEAT' modes with extreme temperature settings to check for proper operation. If issues persist, confirm 24 volts at the low-voltage terminal strip between 'R' and 'C,' 'Y' and 'C,' and 'O' and 'C,' and between 'G' and 'C' in the air handler. Replace the thermostat if it's defective.
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William CrawfordAug 16, 2025
Why does my Bosch SM Split CS turn off due to high pressure?
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  troy35Aug 16, 2025
  Your Bosch Heat Pump might be shutting down due to high pressure for a few reasons. In 'COOLING' mode, check for insufficient water flow, excessively warm entering water temperature, or a scaled/plugged condenser. In 'HEATING' mode, ensure adequate fluid flow on the load side, and verify the blower is operational, the filter isn't clogged, and ductwork isn't restricted. An overcharged refrigerant level can also cause this issue; in that case, reclaim refrigerant, evacuate, and recharge to the factory-recommended level. Finally, inspect the high-pressure switch for defects or improper calibration.
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chenangelaAug 22, 2025
What causes a Bosch Heat Pump to shut off due to low pressure?
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  patrickcookAug 22, 2025
  A Bosch Heat Pump shutting off due to low pressure can be attributed to several factors. In 'COOLING' mode, investigate potential issues such as insufficient airflow, excessively cold entering air temperature, a non-operational blower, a clogged filter, or ductwork restrictions. If in 'HEATING' mode, check for inadequate water flow, excessively cold entering water temperature, or a scaled/plugged condenser. A low refrigerant charge is another possibility; look for refrigerant leaks, repair them, evacuate the system, and recharge with the factory-recommended amount. Lastly, examine the low-pressure switch for any defects or calibration problems.
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Mary ChapmanAug 27, 2025
How to fix a Bosch SM Split CS that short cycles?
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  Rodney FergusonAug 28, 2025
  If your Bosch Heat Pump is short cycling, several factors could be responsible. The unit might be oversized, requiring recalculation of heating or cooling loads. The thermostat's location could be the problem if it's near a supply air grill; try relocating it and adjusting the heat anticipator. Also, check the wiring and controls, specifically looking for a defective or improperly calibrated low-pressure switch.

Summary

Document Conventions

Symbols and Warnings

Defines symbols and keywords for risk assessment and safety precautions.

Safety Warnings

Provides critical safety information for installation, servicing, and operation.

Model Nomenclature

Nomenclature Diagram

Diagram illustrating the breakdown of the SM Split CS heat pump model number.

CS;Air Handler Pairing

Air Handler Model Legend

Defines abbreviations used for various BOSCH air handler models.

SM Split CS Standard Package

General Description and Specifications

Overview of performance, certifications, and system configuration.

Moving, Storage, and Inspection

Guidelines for handling, storing, and inspecting the unit upon arrival.

Unit Installation Guide

Location Selection

Recommendations for optimal placement of air handler and condensing sections.

Condensing Section Installation

Instructions for mounting the condensing section on a suitable base.

Installation Details

Condensate Drain and Water Piping

Procedures for installing condensate drain lines and water piping.

Refrigerant Line Installation

Line Length and Connections

Guidance on routing, sizing, and connecting refrigerant lines.

Refrigerant Charge and Capacity

Valve Sizing and Capacity Multiplier

Charts for valve sizing, refrigerant charge, and capacity adjustments.

Refrigerant Line Adjustments

Liquid Line Charge and Pairing Adjustments

Data for liquid line charge and adjustments for specific air handler pairings.

Refrigerant Adjustment Tables

BMAC and BVA2.0 Adjustments

Tables for charge and TXV adjustments with BMAC and BVA2.0 units.

Airflow Adjustment Data

BMAC TXV and BVA2.0 Airflow

Tables for TXV adjustments with BMAC and airflow ratings for BVA2.0.

Water Quality Table

Acceptable Water Parameters

Table detailing water quality parameters for copper and cupro-nickel.

Electrical Component Layout

Electrical Safety and Wiring

Information on electrical hazards, safety, and wiring requirements.

UPM Controller and Safety Devices

UPM Controller Board Diagram

Diagram illustrating the Unit Protection Module controller board and its components.

UPM Controller Settings and Modes

Default Settings and DIP Switches

Details on UPM board factory default settings and DIP switch functions.

UPM Controller Features

Malfunction, Test, and Freeze Sensor

Explanation of malfunction outputs, test modes, and freeze sensor operation.

Typical System Setup

System Diagram and Components

Diagram illustrating a typical system configuration and its components.

Specific Application Considerations

Well, Cooling Tower, and Geothermal

Considerations for specific water source and loop system applications.

Post-Installation Checkout

System Startup and Operation

Procedures for unit startup and verifying operation in cooling/heating modes.

Sequence of Operation

Description of the unit's operational sequence in different modes.

Sequence of Operation Modes

Cooling and Heating Mode Sequences

Detailed sequence of operation for cooling and heating modes.

Components and Accessories

Pump;Valve Relay and DPS

Description of factory-installed relay and optional Flow Proving Switch.

SmartStart Assist Functionality

Specifications and Operating Modes

SmartStart Assist specifications and diagrams of its operating modes.

SmartStart Assist Operation Notes

LED Indicators and Operational Notes

Explanation of SmartStart Assist LED indicators and operational notes.

SmartStart Assist Troubleshooting

Troubleshooting Guide and Alarms

Information on troubleshooting SmartStart Assist and alarm conditions.

Check-Out Sheet

Data Recording Sections

Sections for recording customer data, unit nameplate, and operating conditions.

Troubleshooting Overview

Common Unit Faults

Table detailing common unit problems, causes, and checks/corrections.

Troubleshooting Specific Issues

Short Cycles and Insufficient Performance

Troubleshooting steps for units experiencing short cycling or poor performance.

SmartStart Assist Troubleshooting

Troubleshooting Table and Flashing Sequence

SmartStart Assist troubleshooting table and flashing sequence diagram.

UPM LED Status Indicators

Blink Codes and Compressor Ohms

Explanation of UPM LED blink codes and compressor ohm readings.

Operating Temperatures and Pressures (SM024)

Cooling Data

Operating conditions for SM024 units in cooling mode.

Heating Data

Operating conditions for SM024 units in heating mode.

Operating Temperatures and Pressures (SM036)

Cooling Data

Operating conditions for SM036 units in cooling mode.

Heating Data

Operating conditions for SM036 units in heating mode.

Operating Temperatures and Pressures (SM048)

Cooling Data

Operating conditions for SM048 units in cooling mode.

Heating Data

Operating conditions for SM048 units in heating mode.

Operating Temperatures and Pressures (SM060)

Cooling Data

Operating conditions for SM060 units in cooling mode.

Heating Data

Operating conditions for SM060 units in heating mode.

Maintenance Procedures

Filter Changes and Annual Checkup

Information on routine maintenance tasks like filter changes and annual checkups.

Water Side Pressure Drop Data

Table showing water side pressure drop for various flow rates and models.

Decommissioning and Disposal

Environmental Protection and Waste

Guidelines for responsible disposal and environmental protection.

Wiring Diagrams

Unit Wiring Diagram

Diagram illustrating the electrical wiring of the SM Split CS heat pump.

Dimensional Drawings

Unit Dimensions and Connections

Diagram showing physical dimensions and connection points of the units.

Terminology and Glossary

Acronyms and Terms Definitions

Definitions of acronyms and technical terms used in the manual.