Trane TR-OHS RCU Series

Questions and Answers

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Joseph HooperAug 17, 2025
What to do if my Trane TR-OHS RCU Air Conditioner Accessories unit fails to start?
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  William Smith PhDAug 17, 2025
  If your Trane Air Conditioner Accessories unit fails to start, there could be several reasons: * Incorrect phasing or voltage: Correct the phase or voltage input. * Power failure: Check the power source, power inlet, and fuses. Also, inspect the control cables and connections. * Overload protection tripped: Determine the cause of the overload and reset the circuit breaker(s) or motor starter protector(s).
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Catherine ConnerAug 20, 2025
Why is my Trane TR-OHS RCU compressor not starting?
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  Alyssa FlowersAug 20, 2025
  If your Trane Air Conditioner Accessories compressor isn't starting, it could be due to several reasons: * The temperature setpoint is too high: Adjust it to the desired temperature. * The compressor internal overload protector is open: Check the compressor for a short circuit or ground. * Complete loss of refrigerant charge: Locate and repair any leaks, then recharge the system. * Condensing unit pressure too high: Check the condensing unit for obstructions and reset the high-pressure switch. * Minimum off time has not expired: Wait for the time to expire.
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Bobby CombsAug 22, 2025
What causes Trane TR-OHS RCU Air Conditioner Accessories to have high head pressure?
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  Tonya DawsonAug 22, 2025
  High head pressure in your Trane Air Conditioner Accessories can be caused by: * Low condensing unit airflow: Open air passages, clean the coil, and check the condensing unit fan(s). * Air or other non-condensible gas in the system: Reclaim the system and recharge it, installing a new drier strainer. * Overcharge of refrigerant: Reclaim excess refrigerant from the system. * Condensing unit fan not operating: Check the main voltage power source to the unit, fan motor starter protector, contactor, fan cycling switch, or fan speed controller.
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scottreyesAug 25, 2025
Why is the condensing unit head pressure too high in my Trane TR-OHS RCU?
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  garciamargaretAug 26, 2025
  If the condensing unit head pressure is too high in your Trane Air Conditioner Accessories, it could be due to: * Non-condensable gas or air in the system: Recover the system, evacuate it, and recharge. Install a new drier/strainer. * Low condensing unit airflow: Open air passages, clean the coil, and check the condensing unit fan(s). * Overcharge of refrigerant: Reclaim excess refrigerant from the system. * Condensing unit fan not operating: Check the main voltage power source to the unit, fan motor starter protector, contactor, fan cycling switch, or fan speed controller; replace as needed. * Condensing unit pressure regulating valve setting too high: Adjust to obtain the correct pressure.
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Gabriela MartinAug 27, 2025
Why is the suction pressure too low in my Trane TR-OHS RCU?
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  Jessica PalmerAug 28, 2025
  Low suction pressure in your Trane Air Conditioner Accessories could be due to: * Loss of refrigerant: Locate the leak and repair it. Recharge the system. * Expansion valve stuck or obstructed: Remove and clean or replace the valve. * Clogged drier/strainer: Replace with a new drier/strainer. * Dirty air filters: Clean or replace the filters on the AHU.
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cody93Aug 30, 2025
Why is my Trane Air Conditioner Accessories compressor short cycling?
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  Charlene WillisAug 30, 2025
  If your Trane Air Conditioner Accessories compressor is short cycling, consider these potential causes: * Low line voltage: Check the power source for the cause of low line voltage. * Dirty or iced-over evaporator coil: Defrost and clean the evaporator/heat exchanger. * Reduced airflow: Check the filter and belt tension. * Lack of refrigerant: Check for a leak, repair it, and recharge the system. * Short cycling of conditioned air: Increase the heat load. * Remote temperature sensor improperly located: Check for supply registers that may be too close to the thermostat; relocate if necessary.
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Daniel LeeSep 2, 2025
Why is the suction pressure too low on my Trane Air Conditioner Accessories?
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  Robert BuchananSep 2, 2025
  If the suction pressure is too low on your Trane Air Conditioner Accessories, it could be due to: * Expansion valve not opening fully: Open air passages, clean the coil, and check the condensing unit fan(s). * Low charge, flash gas in liquid line: Reclaim system and recharge. Install a new drier strainer. * Clogged drier/strainer: Reclaim excess refrigerant from system. * Obstructed expansion valve: Check the main voltage power source to the unit and the fan motor starter protector, contactor, fan cycling switch or fan speed controller.
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mitchellmeghanSep 5, 2025
Why is my Trane TR-OHS RCU system short of capacity?
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  melissamarshSep 5, 2025
  If your Trane Air Conditioner Accessories system is short of capacity, it may be due to: * Low refrigerant: Check for leaks, repair, and recharge the system. * Expansion valve stuck or obstructed: Remove the valve and clear any obstruction, or replace the valve. * Reduced airflow: Check belt tension, filters, and clear the evaporator coil of debris.
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Troy CastilloSep 7, 2025
What could cause a noisy compressor in Trane TR-OHS RCU?
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  Matthew CarrSep 7, 2025
  A noisy compressor in your Trane Air Conditioner Accessories could stem from: * Expansion valve stuck in the open position: Check the operation of the expansion valve and superheat. * Worn or scarred compressor bearings: Replace the compressor. * Broken compressor valve: Replace the compressor. * Liquid slugging: Ensure the expansion valve is not stuck in the open position and that the system is not overcharged; reclaim excess refrigerant. * Scroll compressor not properly phased: Phase correctly at the main power source; do not rewire the compressor.
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Jeanne MitchellSep 10, 2025
Why is the condensing unit head pressure too low in my Trane TR-OHS RCU?
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  Ryan MyersSep 12, 2025
  If you're experiencing low condensing unit head pressure in your Trane Air Conditioner Accessories, it might be caused by: * Loss of refrigerant: Locate and repair the leak, then recharge the system. * Condensing unit fan controls not set properly: Adjust or repair the controls. * Control pressure set too low: Readjust to 320 psig for R407C.

Summary

Model Number Descriptions

Introduction to Remote Condensing Units

General Unit Overview

Describes the two RCU versions (indoor/outdoor) and their intended applications.

Product Description and Features

Details the construction, components, and design aspects of the RCU units.

RCU Application Ranges

Specifies the operating temperature, voltage, and piping length limits for RCUs.

Key Design Components

Explains major components like compressor, coil, fan assembly, and electric box.

Unit Safety Features

Covers disconnect switches, pressure switches, and motor protection devices.

Installation Procedures for RCUs

Equipment Receiving and Inspection

Instructions for inspecting the RCU unit upon delivery for any transit damage.

Site Selection and Preparation

Guidelines for choosing a secure location with adequate service access.

Rigging and Lifting Safety

Critical safety precautions and methods for lifting and moving the RCU unit.

Mounting and Placement Guidelines

Procedures for securing RCU-O on flat surfaces and RCU-I in ceiling grids.

Refrigerant Piping Connections

Details on connecting suction/liquid lines, brazing, supports, and leak testing.

Refrigerant Pipe Sizing

Tables and guidelines for sizing refrigerant lines based on capacity and distance.

Suction and Liquid Line Details

Specific instructions for sizing suction/liquid lines, including traps and velocities.

Utility and Wiring Connections

Information on power supply, control wiring, voltage options, and grounding.

Electric Box Component Layout

Overview of electrical components and their locations within the RCU's electric box.

System Charging and Refrigerant Handling

DX Charging Best Practices

Essential techniques and safety measures for performing DX charging.

R407 C Refrigerant Properties

Information on R407C's environmental impact and handling precautions.

System Preparation for Charging

Steps for leak testing, evacuating, and preparing the system before charging.

Refrigerant Charging Procedures

Step-by-step guide for safely adding refrigerant to the RCU system.

Estimating Refrigerant Charge Amount

Methods for calculating the correct refrigerant quantity needed for the system.

Initial and Fine-Tuning Charge

Procedures for initial charge and adjusting superheat/sub-cooling.

Flooded Head Pressure Control Charging (-30°F)

Specific charging steps for units operating with -30°F flooded head pressure control.

Refrigerant Characteristics and System Settings

R407 C Pressure-Temperature Data

Tables detailing normal, min, and max pressure/temperature settings for R407C.

System Settings and Controls

Explains pressure switches, fan cycling, head pressure control, and hot gas bypass.

Commissioning, Decommissioning, and Operation

Unit Operation and Start-Up

Pre-start-up checklist, personnel requirements, and step-by-step start-up.

Refrigeration Cycle Description

Explanation of the RCU's refrigeration cycle and how the unit operates.

Decommissioning and Refrigerant Recovery

Procedures for safely decommissioning the unit and recovering refrigerant.

Labeling Decommissioned Equipment

Requirements for labeling units that have been emptied of refrigerant.

Maintenance Procedures

Periodic General Maintenance

Routine checks for electrical connections, refrigerant, and unit cleanliness.

Compressor Component Care

Procedures for checking compressor oil, refrigerant charge, and potential leaks.

Blower Belt Adjustment and Speed Control

Steps for adjusting blower belt tension and fan speed using sheaves.

Troubleshooting and Repair Guide

Control and Unit Start-Up Diagnostics

Diagnosing erratic controls, unit start failures, and overload conditions.

Head Pressure Troubleshooting

Resolving high and low head pressure issues with probable causes and solutions.

Suction Pressure and Refrigerant Level Issues

Addressing low suction pressure and refrigerant leaks.

Compressor Performance Diagnostics

Solutions for noisy compressors, start failures, short cycling, and capacity loss.

Field Service and Leak Repair

Methods for detecting and repairing refrigerant leaks in field service.

Component Replacement and Cleanup Procedures

Guidance for replacing major components and performing acid cleanup.

Product Support and Maintenance Planning

Product Support Services and Warranty

Information on technical support, warranty authorization, and parts ordering.

Recommended Maintenance Schedules

Schedule of monthly, semi-annual, and annual maintenance tasks.

Completed Installation Verification Checklist

A checklist for verifying all installation steps are properly completed.