Introduction and Overview of HVAC Systems Course 106

Transcription

1 LY N O W IE PR EV Introduction and Overview of HVAC Systems Course 106 PARTICIPANT GUIDE

2 Introduction and Overview of HVAC Systems Participant Guide Rail Car Training Consortium COURSE 106 July 2016 Draft

3 Table of Contents Module 1... iv General Safety Procedures for HVAC Maintenance Overview of Rail car HVAC Maintenance EPA Regulations, Refrigerant hazards and proper handling Personal Protective Equipment General Safety Rules and Procedures Summary...24 Module Background Knowledge Overview Basic Theories of Heat Refrigeration and Air Conditioning Heating System HVAC Piping and Tubing Summary...58 Module Tools Overview Tools Summary...72 Page iii

4 LIST OF FIGURES Figure 1.1: Common Transit Rail HVAC Systems... 2 Figure 1.2: Split HVAC System Diagram (Courtesy of MBTA) Note: Not all HVAC Components are Marked... 3 Figure 1.3: Split Rail Car HVAC - Left: Condenser; Middle: Compressor and Motor; Right: Evaporator Blower Motor (Courtesy of GCRTA)... 3 Figure 1.4: Sutrak Roof Mount Rail Car HVAC Unit Older Model (Courtesy of San Diego MTS)... Error! Bookmark not defined.4 Figure 1.5: ThermoKing Roof Mount Light Rail HVAC Unit (Courtesy of CATS)... Error! Bookmark not defined.4 Figure 1.6: Section 608 Requirements (Source: EPA Fact Sheet)... 7 Figure 1.7: Sample Refrigerant Safety Data Sheet (SDS) Figure 1.8: Heavier-than-Air Gas Displacing Oxygen Figure 1.9: Frostbite Figure 1.10: Goggles Figure 1.11: Full Face Shield Figure 1.12: Gloves Figure 1.13: Electrical Hazard Safety Shoes Figure 1.14: Self-contained breathing apparatus (SCBA) Figure 1.15: Job Card for HVAC Extensive (Courtesy of Tri-Met) Figure 1.16: Lockout/Tagout Kit Figure 1.17: Electrical Cutout Box with Lock (Courtesy of MBTA) Figure 1.18: Multiple Lockouts (Courtesy of CATS) Figure 1.19: Pinch Point Figure 1.20: Condenser Coil Fins (Courtesy of MBTA) Figure 1.21: Fire Extinguisher (Courtesy of CATS) Figure 1.22: Fire Extinguisher (Courtesy of WMATA) Figure 2.1: Excerpt of Temperature Pressure Chart from Parker Hannifin Corporation Figure 2.2: Generic Air Conditioning System Figure 2.3: AC Refrigeration Cycle Figure 2.4: Classification of Main Refrigerants Figure 2.5: Commonly Used Refrigerant in Transit Rail HVAC Systems Figure 2.6: HVAC Controller Regular Diagram with Heaters (Courtesy of CATS) Figure 2.7: Heater Modes Configuration Table (Courtesy of CATS) Figure 2.8: Integrated Heater Coils(resister element) (Courtesy of Denver RTD) Figure 2.9: Integrated Heater Coils (Courtesy of CATS) Figure 2.10: Forced Air Floor Heater (Courtesy of Denver RTD) Figure 2.11: Forced Air Floor Heater without Cover (Courtesy of Denver RTD) Figure 2.12: Radiant Floor Heater (Courtesy of Denver RTD) Figure 2.13: Radiant Floor Heater with Cover Pulled Open (Courtesy of Denver RTD) Figure 2.14: Under-the-seat Forced-air Heater (A), Heater Cage (B), and Heater Coils (C) (Courtesy of Sacramento Regional Transit) Figure 2.15: Thermal Switch (Courtesy of CATS) Figure 2.16: Fusible Link in Holder (Courtesy of MBTA) Figure 2.17: Fusible Link (Courtesy of MBTA) Figure 2.18: Cab Heater (Courtesy of Denver RTD) Page iv

5 MODULE 1 Outline RAIL VEHICLE COURSE 106: INTRODUCTION AND OVERVIEW OF HVAC SYSTEMS MODULE 1: GENERAL SAFETY PROCEDURES FOR HVAC MAINTENANCE General Safety Procedures for HVAC Maintenance 1-1 Overview of Rail Car HVAC Maintenance 1-2 EPA Regulations, Refrigerant Hazards and Proper Handling 1-3 Personal Protective Equipment 1-4 General Safety Procedures and Rules 1-5 Summary Purpose and Objectives The purpose of this module is to provide participants with a basic understanding of the hazards and proper handling of refrigerant, Personal Protective Equipment (PPE) generally used by HVAC technicians, and safety rules and procedures related to HVAC maintenance. Following the completion of this module, the participant should be able to complete the objectives with an accuracy of 75% or greater: Demonstrate knowledge of Clean Air Act of 1990, EPA 608 Certification, Refrigerant Hazards and Proper Handling Techniques Explain types and use of Personal Protective Equipment (PPE) when dealing with HVAC systems List safety rules related to HVAC maintenance Key Terms Clean Air Act of 1990 Environmental Protection Agency (EPA) Section 608 Certification Toxicity Exposure Heavier than Air Flammable Refrigerant Combustible Refrigerant Asphyxiation Decomposition Personal Protective Equipment (PPE) Self-contained Breathing Apparatus (SCBA) Lockout/Tag out Pinch point Electrical Hazards Page 1

6 MODULE 1: GENERAL SAFETY PROCEDURES FOR HVAC MAINTENANCE Motor Person Console Sealed Switch Panel Blower Evaporator Ceiling Transition Ceiling Transition Duct Return Air Plenum Liquid & Suction Lines Drain Line Fresh Air Intake Blower Evaporator Compressor & Condenser Unit (under the car) Temperature & Motor Control Box Drain Line Figure 1.2: Split HVAC System Diagram (Courtesy of MBTA) Note: Not all HVAC Components are Marked Figure 1.3: Split Rail Car HVAC - Left: Condenser; Middle: Compressor and Motor; Right: Evaporator Blower Motor (Courtesy of GCRTA) By comparison, a unitized (or modular, packaged, self-contained) HVAC system is a stand-alone unit and can be easily exchanged for service ( and ). Unitized or packaged systems are designed such that all refrigeration components and piping are contained within a single module. The number of units on a particular car may vary, depending on the car configuration. In most cases, a single vehicle has two HVAC units, one at each end. Multi-sectioned articulated vehicles often have one HVAC unit per car section. However, smaller vehicles, such as low floor street cars, may have two smaller units per section, due to the limited roof area and necessity to locate other equipment on the roof. Unitized systems are most commonly installed on the vehicle roof but can also be installed under the floor of the vehicle. In underfloor installations, recirculated and conditioned air is connected to the passenger area through ducts in the vehicle floor and walls. Unitized or packaged systems facilitate the installation and removal of the HVAC unit on the vehicle. In addition to the mechanical mounting hardware, only the electrical, ducting, and drain Page 3

7 MODULE 2 Outline 2-1 Overview RAIL VEHICLE COURSE 106: INTRODUCTION AND OVERVIEW OF HVAC SYSTEMS MODULE 2: BACKGROUND KNOWLEDGE 2-2 Basic Theories of HV 2-3 Refrigeration and Air Conditioning 2-4 Heating System 2-5 HVAC Piping and Tubing 2-6 Summary Purpose and Objectives Background Knowledge The purpose of this module is to provide participants with the background knowledge and theories necessary for rail HVAC maintenance. Following the completion of this module, the participant should be able to complete the objectives with an accuracy of 75% or greater: Demonstrate knowledge of the basic theories of heat Describe the basic concepts of refrigeration and air conditioning Describe the basic components and basic concepts of a typical heating system Demonstrate basic knowledge of HVAC piping and tubing Key Terms Heat Temperature Heat Transfer Change of State Latent Heat Thermal Kinetic Energy Sensible Heat Super-heat Saturation Temperature Sub-cooling Compressor Condenser Expansion Valve/Metering Device Evaporator Refrigeration Cycle Refrigerant Heater Thermal Cutout/Switch Circuit Breaker Thermal Fuse Fusible Link Hard-drawn Copper Soft Copper Brazing Soldering Hard/Silver Soldering Soft Soldering Solder Flux Oxygen/Acetylene Air/Acetylene MAPP Gas Page 27

8 MODULE 2: BACKGROUND KNOWLEDGE Figure 2.6: HVAC Controller Regular Diagram with Heaters (Courtesy of CATS) Electrical Heating Elements Figure 2.7: Heater Modes Configuration Table (Courtesy of CATS) PREVIEW Electric heat is produced by converting electrical energy to heat. This is done by placing a known resistance of a particular material in an electric circuit. The resistance has relatively few free electrons and does not conduct electricity easily. The resistance to electron flow produces heat at the point of resistance. One type of material commonly used in electric heating is nichrome, which is short for nickel chromium. Wire made from nichrome is used in the majority of electric heaters. For example, 80% nickel and 20% chromium are used for some rail car HVAC heater coils. Electric heat is very efficient but can be more expensive to operate compared to other sources of heat. It is efficient because very little electrical energy is lost from the meter to the heating element and there are no chimney losses as in the case of fossil-fuel heating systems. It is expensive because it takes large amounts of electrical energy to produce the heat, and the cost of electrical energy in most areas of the country can be expensive compared to fossil fuels (coal, oil, and gas). Although other types of heating elements can be used, such as hydronic (heated water), most current rail car HVAC systems are designed with electrical heating. ONLY Page 41

9 MODULE 2: BACKGROUND KNOWLEDGE There are several ways to prevent heat damage to nearby HVAC components during soldering or brazing. Some HVAC technicians use a combination of these techniques to minimize potential damage: Wet rags and water spray (Figure 2.27): Offers some protection but often not as effective as the two methods below. Cool Gel (Figure 2.28): Unique gelled formula sticks to surfaces without drips and protects adjoining areas of wood, wallboard, insulation etc. Heat Sink Compound/Paste (Figure 2.29): Protective heat sink compound confines heat to the welding, brazing or soldering zone. It effectively absorbs surface heat generated by welding, brazing or soldering on metals and other materials. It eliminates heat damage, prevents buckling, warping or other distortions of light gauge material and cleans up with water. Technicians may also consider disassembling parts like the Thermal Expansion Valve (TXV) prior to brazing and soldering to avoid damage. Figure 2.27: Wet Rag Wrapped Around TXV to Avoid Overheating Safety Precaution Figure 2.28: LA-Co Cool Gel Figure 2.29: Heat Sink Compound Warning: Safety Precautions! It is important to note that all safety precautions should be applied when brazing HVAC pipes including safety glasses and fire extinguishing equipment. Safety is always first when doing any job in HVAC and especially when dealing with oxyacetylene equipment and brazing. Page 56

10 MODULE 3 Outline 3-1 Overview 3-2 Tools 3-3 Summary Purpose and Objectives RAIL VEHICLE COURSE 106: INTRODUCTION AND OVERVIEW OF HVAC SYSTEMS MODULE 3: TOOLS Tools The purpose of this module is to provide participants with an overview of the tools used for rail HVAC maintenance. Following the completion of this module, the participant should be able to complete the objectives with an accuracy of 75% or greater: Explain the use of o Temperature measuring device o Acid test kit o Refrigerant recovery/recycle machine o Two-stage vacuum pumps o Pressure and vacuum micron gauge o Manifold gauge set o Refrigerant leak detectors o Breakout box o Air flow hood, anemometer or other velocity/volume-measuring device o Scale o Tubing, brazing and soldering tools o Portable test unit Key Terms Thermometer Acid Test Kit Refrigerant Recovery/Recycle Machine Vacuum pump Pressure/Vacuum gauge Manifold gauge Leak detector Breakout box Thermo-anemometer Velocity Oxyacetylene Air-acetylene MAPP gas Page 60

11 MODULE 3: TOOLS Acid Test Kit The acids sometimes found in refrigerants can be formed by chemical reactions with components and/or materials of construction, lubricating oils, and/or impurities. The instability of the refrigerant, and thus the formation of acids, is accelerated by elevated temperatures which could be the result of improper operation, such as a failed condenser fan or clogged airflow path. Checking the system for acid should be a routine maintenance practice, because acid can be easily treated before the compressor fails. You can check the refrigerant oil for acid, or you can check the refrigerant for the acid. Rail HVAC OEMs generally recommend checking refrigerant oil. If you decide to use an oil acid test kit (Figure 3.3and Figure 3.4), be aware that using the wrong type of test kit with an ester-based (POE) oil can result in a false acid reading, because the oil behaves like an acid to the test kit (that is, the ester oil displays amphoteric properties). That s why many oil acid test kits have one kit (or one scale) for mineral oils and a different test kit (or scale) for POE oils. Figure 3.3: Acid Test Kit Refrigerant Recovery/Recycle Machine Figure 3.4: Color Indicators of an Acid Test A refrigerant recovery/recycle machine can remove refrigerant from an AC system, test for leaks, measure oil content, purge the system and replace refrigerant and oil. Newer machines can do all this automatically. There are two basic types of recovery devices. A system-dependent device captures refrigerant with the assistance of components in the equipment from which refrigerant is being recovered. A self-contained machine has its own means to draw the refrigerant out of the equipment (a compressor). Most of the system-dependent machines are used in over-the-road applications. Rail agencies normally use self-contained recovery and recycling machines. Below are examples of refrigerant recovery and reclaim machines used on transit properties. Page 62