Trane Thermafit AXM - User Manual

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Overview

Function Description
Important Technical Specifications
Usage Features
Maintenance Features

This document describes the Trane Thermafit™ Modular Air-to-Water Heat Pump, Model AXM, a system designed for efficient heating and cooling in commercial and residential applications. The manual provides comprehensive information on installation, operation, and maintenance, emphasizing safety and proper handling of the equipment.

Function Description

The AXM heat pump system is a modular air-to-water unit that addresses varying cooling and heating demands in HVAC systems. It can operate in either cooling or heating mode, depending on building needs, and does not simultaneously heat and cool. In cooling mode, it produces cold water, with the air-source coils rejecting heat. In heating mode, it produces hot water, with the air-source coils facilitating heat transfer from the environment. The system is designed for outdoor installation and utilizes independent refrigeration circuits in each module.

Important Technical Specifications

Capacity: Available in 30 nominal ton capacity modules.
Modularity: A minimum of 2 and up to 10 modules can be connected in a standard primary/secondary control system.
Refrigerant: Uses R-454B, which is a flammable (A2L) refrigerant. Specific handling procedures and R-454B rated service equipment are required.
Refrigeration Circuits: Each module features dual independent refrigeration circuits.
Compressors: Equipped with two vapor-injected scroll compressors per module, featuring suction gas-cooled motors with thermistors for overload protection. Compressors are mounted with rubber-in-shear vibration isolators.
Heat Exchanger: Load brazed-plate heat exchanger (BPHE), typically made of SAE Grade 316 stainless steel and 99.9% copper brazing materials.
Air Coils: Aluminum fins mechanically bonded to copper tubes with integral subcooling circuits, factory tested to a minimum of 700 psig.
Fans: Highly efficient Electronically Commutated Motors (ECM) that vary speed to maintain refrigeration head pressure. Airflow is 23,000 cfm/module.
Fluid Volume (Load): 18.44 gallons per module.
Refrigerant Charge: 86 lbs per module.
Operating Temperatures:
- Heating: 90-140°F leaving water/brine.
- Cooling: 42-65°F leaving water/brine.
Operating Pressure (Water/Brine): Minimum 0 psig, Maximum 200 psig (standard option), 300 psig (hi pressure option).
Dimensions (30 tons AXM): A: 103 inches, B: 95 inches, C: 48 inches, D: 90 inches.
Weight: 3500 lbs per module.
Water Quality Guidelines: pH 7.5-9.0, Conductivity < 500 µS/cm, Total Hardness 4.5-8.5 dH°, Free Chlorine < 1.0 ppm, Ammonia (NH3) < 0.5 ppm, Sulphate (SO42-) < 100 ppm, Hydrogen Carbonate (HCO3-) 60-200 ppm, Chloride (Cl-) < 200 ppm.
Glycol Concentration: Recommended propylene glycol concentrations for freeze protection range from 18% (20°F) to 46% (-20°F) for burst protection.

Usage Features

Control System: Utilizes Carel c.pCO series microprocessor controllers for monitoring and reporting critical operating parameters. A primary controller coordinates secondary modules.
Touchscreen Interface Panel: The primary means for controlling and monitoring the system, allowing operators to adjust set points, clear alarms, and perform detailed setup. It displays real-time information about the chiller and module parameters.
BMS Communication Options: Supports BACnet® MS/TP, BACnet IP, Modbus RTU, Modbus IP, and LonWorks® (BMS not standard, available as an option).
Distributed Control: Secondary controllers can operate independently if the primary controller fails, preserving safeties like temperature set point, refrigerant pressures, and freeze protection.
Module Staging: Compressors stage up and down based on demand, with a LIFO (Last In First Out) sequence for staging down.
Defrost Mode: Modules intermittently enter defrost mode in heating operation at low ambient temperatures to prevent frosting of air-source coils, minimizing impact on heating capacity.
Flow Switch: Equipped with a flow switch to detect liquid flow, preventing compressors from starting if there is no flow.
Phase Monitor: Protects against under-voltage, voltage imbalance, phase loss, and phase reversal in three-phase power systems.
Solenoid Valve: Liquid-line solenoid valve provides a refrigerant pump-down cycle to prevent liquid refrigerant migration to the compressor during off-cycle.
Reversing Valves: Electro-mechanical 4-way valves reverse refrigerant flow for heating or cooling, designed to minimize pressure difference and leakage.
Electronic and Manual Isolation Valves: BPHE branch lines include manual inlet and electronic discharge butterfly valves for variable primary flow, with a minimum opening cycle time of 30 seconds.

Maintenance Features

Maintenance Strategy: Emphasizes preventive maintenance with three levels: frequent "health checks" (daily/weekly visual and manual inspections), periodic maintenance (monthly cleaning and fluid inspection), and overhaul maintenance (scheduled component replacement).
Alarm Monitoring: The touchscreen interface displays active alarms and an alarm history, allowing for quick identification and troubleshooting of issues. Alarms can be filtered by status and state.
Strainer Cleaning: Strainers on the inlet water pipe should be cleaned periodically (weekly after startup, then as needed) to protect heat exchangers and maintain fluid cleanliness. Service isolation valves allow cleaning without disrupting other modules.
Air Coil Cleaning: Coils should be cleaned using a garden hose with a spray nozzle (not a pressure washer) to remove dirt and debris. Chemical soaking may be required for extremely dirty coils.
Heat Exchanger Cleaning: Trane recommends using SWEP Goodway® Technologies ScaleBreak-MP, an industrial biodegradable descaler, circulated through water passages to dissolve calcium, lime, rust, and other deposits.
Refrigerant Handling: Requires trained service personnel, specific R-454B rated equipment, and adherence to local/federal regulations for recovery, charging, and disposal due to flammability.
Oil Level Check: Compressor oil level sight glass allows visual inspection of oil, which should be clear and free-flowing. Milky appearance indicates liquid refrigerant in the compressor.
Glycol Maintenance: Water/glycol mixture quality and cleanliness must be monitored. Glycol should be removed for extended storage. Special inhibitors are recommended for glycol-free solutions.
Electrical Inspection: Regular checks of electrical connections, fuses, overload settings, and wiring are required to ensure safety and proper operation.
Compressor Diagnostics: Compressors have solid-state protection with PTC internal sensors for motor protection. KRIWAN flash codes provide quick status display and troubleshooting for compressor errors.
Vacuum Evacuation: Required to remove moisture from the system to prevent corrosion and performance degradation.
Initial Start-Up Agreement: Trane factory-certified technicians perform initial start-up, requiring a completed form and confirmation that all critical work is functional.