Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Piping, Ducting and Trunking
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Piping, Ducting and Trunking
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Subject: Air Conditioning And Refrigeration
Class: Senior Secondary 2
Term: 3rd Term
Week: 2
Theme: Installation Process
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Definition: Piping refers to the system of pipes, fittings, valves, and other components used to convey liquids (e.g., water, oil) and gases (e.g., refrigerants, natural gas) from one point to another within a system. In HVAC-R, it primarily refers to the refrigerant lines and sometimes water lines in chilled water systems.
Purpose: To transport refrigerant between components (compressor, condenser, expansion device, evaporator) in a closed loop, or to carry chilled/hot water for heat exchange.
Common Materials: Copper Tubing (most common in refrigeration): Properties: Excellent heat conductivity, corrosion resistance, ease of fabrication (bending, flaring, brazing).
Types: Soft Copper (Annealed): Easily bent by hand or with a tube bender. Available in coils (e.g., 25-50ft lengths). Suitable for smaller diameter lines and where flexibility is needed (e.g., connecting indoor and outdoor units of split ACs).
Hard Copper (Drawn): Rigid, comes in straight lengths (e.g., 10-20ft). Requires fittings (elbows, couplings) for changes in direction. Used for larger diameter lines or where rigidity is preferred.
Sizes: Specified by Outer Diameter (OD), e.g., 1/4", 3/8", 1/2", 5/8", 3/4", 7/8". These are standard in Nigeria for residential and light commercial AC units.
Application: Refrigerant lines (suction, liquid, discharge lines) in almost all refrigeration and air conditioning systems, from domestic fridges to industrial chillers. Steel Pipes (Carbon Steel/Stainless Steel): Properties: High strength, suitable for high pressure and large diameter applications.
Application: Industrial refrigeration systems, large chilled water piping, steam lines. Not common for residential refrigerant lines due to corrosion and fabrication difficulty.
PVC (Polyvinyl Chloride)
Pipes: Properties: Lightweight, corrosion-resistant, low cost, easy to join (solvent welding).
Application: Primarily for condensate drain lines in air conditioning systems (e.g., draining water from the indoor unit of a split AC), as they cannot withstand refrigerant pressures or temperatures.
Joining Methods for Copper Piping: Brazing/Soldering: Most common and reliable method for refrigerant lines.
Brazing: Uses filler metals (e.g., silver alloy, copper-phosphorus alloys) with melting points above 450°C. Creates a very strong, leak-tight joint. Requires a torch (oxy-acetylene or propane/MAPP gas).
Soldering: Uses filler metals (e.g., tin-lead, tin-silver) with melting points below 450°C. Not suitable for high-pressure refrigerant lines but can be used for water or condensate lines.
Flaring: Involves expanding the end of a soft copper tube into a cone shape, which is then sealed against a flared fitting (e.g., flare nut) using a compression joint.
Application: Common for connecting refrigerant lines to split unit AC indoor/outdoor units, where quick disassembly might be needed.
Tools: Flaring tool, tube cutter, reamer.
Swaging: Method to enlarge one end of a tube to fit over another tube of the same diameter, allowing for a brazed joint without needing an additional coupling. Reduces the number of joints.
Tools: Swaging tool, tube cutter.
Mechanical Connections: Threaded fittings (for steel pipes), compression fittings (for smaller lines, sometimes used for water but less common for refrigerant).
Essential Tools for Copper Piping: Tube Cutter: For cutting copper tubing cleanly and squarely.
Reamer/Deburring Tool: To remove burrs from the inside edge of a cut tube, preventing turbulence and pressure drop.
Tube Bender: For bending soft copper tubing without kinking or deforming it.
Flaring Tool Kit: For creating precise flare connections.
Swaging Tool Kit: For expanding tube ends for brazing.
Brazing Torch Kit: For brazing copper pipes (e.g., oxy-acetylene torch, MAPP gas torch).
Manifold Gauge Set: For measuring system pressures during installation and servicing.
Vacuum Pump: For evacuating the system to remove non-condensable gases and moisture.
Leak Detector: Electronic or soap bubble solution for finding refrigerant leaks.
Nitrogen Cylinder with Regulator: For purging the system during brazing (to prevent oxidation) and for pressure testing.
Hacksaw: For cutting larger diameter or rigid pipes.
Definition: Ducting refers to a system of channels or conduits, typically rectangular, round, or oval, used to convey conditioned air (heated, cooled, or ventilated) from an air handling unit (AHU) or furnace to the various spaces within a building.
Purpose: To distribute conditioned air efficiently and evenly throughout a building, and to return stale air to the AHU for reconditioning or exhaust.
Common Materials: Galvanized Steel: Properties: Most common material. Durable, rigid, fire-resistant. Galvanization (zinc coating) prevents corrosion.
Application: Centralized air conditioning systems in commercial buildings, industrial facilities (e.g., large office blocks, shopping malls in Abuja or Lagos).
Shapes: Can be fabricated into rectangular, round, or spiral oval ducts.
Aluminum: Properties: Lighter than steel, corrosion-resistant (good for humid environments), easy to work with.
Application: Sometimes used in smaller or specialized applications, or where weight is a concern. Fibreglass Duct Board (Pre-insulated Duct Panels): Properties: Made from rigid fibreglass insulation covered with a foil vapor barrier. Provides both air conveyance and insulation in one material. Lightweight, good thermal and acoustic properties.
Application: Residential and light commercial applications where insulation is critical and space might be limited.
Flexible Ducts: Properties: Made of a wire coil covered with a flexible plastic or metalized fabric. Highly flexible, easy to install in tight spaces.
Application: Used for short runs to connect rigid ducts to diffusers/grilles, or where minor adjustments in routing are needed. Not ideal for long runs due to higher pressure drop.
Duct Components: Straight Ducts: Main sections.
Elbows: To change direction.
Reducers/Increasers: To change duct size.
Take-offs: To branch off main ducts.
Plenums: Large boxes at the air handler for air distribution/collection.
Grilles/Diffusers: Terminal devices in conditioned spaces for air supply/return.
Dampers: To regulate airflow. Essential Tools for Ducting (Sheet Metal Fabrication): Tin Snips (Straight, Left, Right): For cutting sheet metal.
Duct Crimpers: To create crimps on duct ends for easy fitting.
Duct Seamers/Hand Folders: For forming seams and bends in sheet metal.
Cleat Folders: For forming standing seams.
Pop Rivet Gun: For joining sheet metal pieces with rivets.
Drill: For pilot holes. Measuring Tape, Scribe, Hammer.
DDuct Sealant/Mastic: For sealing duct joints to prevent air leaks. Self-Tapping Screws, Pop Rivets: For fastening duct sections.
Aluminum Foil Tape (Duct Tape): For sealing joints and insulating.
Insulation Material: For external insulation of metal ducts (e.g., fibreglass blankets, foam boards).
Hangers and Supports: For suspending ducts from ceilings.
Definition: Trunking (or conduit/cable management system) refers to enclosed channels, usually rectangular or square in cross-section, used to protect and organize electrical cables, small pipes (like refrigerant lines), and condensate drain lines, typically run along walls or ceilings.
Purpose: To provide a neat, protected, and accessible pathway for services, enhancing aesthetics, safety, and ease of future maintenance or modifications.
Common Materials: PVC (Polyvinyl Chloride)
Trunking: Properties: Most common. Lightweight, easy to cut and install, non-conductive, corrosion-resistant, available in various sizes and colours (white being most common).
Application: Widely used for surface mounting electrical wiring, refrigerant pipes, and condensate drains for split unit AC installations in homes, offices, and small shops.
Galvanized Steel Trunking: Properties: Strong, durable, provides better protection against physical damage.
Application: Industrial settings, workshops, or where mechanical protection is paramount.
Aluminum Trunking: Properties: Lighter than steel, aesthetically pleasing, corrosion-resistant.
Application: Premium installations, offices where aesthetics are critical. Types of Trunking (by application/installation method): Surface Trunking: Mounted directly on the surface of walls or ceilings. Most common for AC installations.
Dado Trunking: Designed to be installed at dado rail height, often incorporating power sockets and data points.
Skirting Trunking: Installed along the base of walls, blending with skirting boards.
Cable Tray: Open, perforated trays used for supporting large bundles of cables, more common in industrial or commercial large-scale electrical installations. Essential Tools and Materials for Trunking: Hacksaw or PVC Cutter: For cutting trunking sections cleanly. Measuring Tape, Pencil, Spirit Level: For accurate layout and alignment.
Drill and Drill Bits: For making holes for screws and wall plugs.
Screwdriver: For fastening trunking to walls.
Trunking Connectors: Couplers: To join straight sections.
Internal/External Corners: For routing around corners.
T-junctions: For branching off.
End Caps: To provide a neat finish.
Screws and Wall Plugs (Rawlplugs): For securing trunking to walls. Adhesive (e.g., contact adhesive or silicone sealant): Can be used for PVC trunking in some applications for extra security or sealing. Worked
Example: Differentiating the Concepts Imagine a new building project in Lagos, a multi-story office complex being designed for a major corporation.
Challenge 1: How will conditioned air from the large central air handling units on the roof reach all the offices on different floors?
Solution: This requires Ducting. Large rectangular galvanized steel ducts will be fabricated and run through ceiling plenums and wall shafts to distribute the cool air to each office zone. Smaller flexible ducts will then connect these main ducts to individual diffusers in each office.
Challenge 2: The building also has a chilled water system for cooling. How will the chilled water be circulated from the chiller plant to the air handling units?
Solution: This requires Piping. Large diameter steel pipes (insulated to prevent condensation) will be used to transport the chilled water from the chiller plant to the various air handling units throughout the building. Smaller copper pipes might be used for refrigerant lines within the AHUs themselves.
Challenge 3: For individual split unit air conditioners installed in some executive offices (as supplementary cooling or for specific zones), how will the refrigerant lines and electrical cables be neatly and safely routed along the finished interior walls?
Solution: This requires Trunking. White PVC surface trunking will be installed along the walls to enclose and protect the copper refrigerant pipes, electrical power cables, and the condensate drain hose, providing a clean and professional appearance. --- This section provides a detailed breakdown of piping, ducting, and trunking, including their definitions, materials, applications, and associated tools.
Understanding piping, ducting, and trunking is not just theoretical; it has direct and tangible applications across various sectors in Nigeria. Residential and Commercial Air Conditioning Installation and Maintenance: Integration: Every home, office, or small business in Nigeria that uses a split unit air conditioner relies on proper piping for refrigerant circulation and trunking for neat and protected installation of lines on walls. Technicians skilled in these areas are in high demand across Nigerian cities for installation, repair, and routine maintenance (e.g., unblocking condensate drain lines which are often PVC pipes within trunking).
Impact: Ensures comfort, energy efficiency, and prevents unsightly or hazardous exposed lines. Cold Storage and Food Preservation Facilities: Integration: Nigeria's vast agricultural sector and growing food processing industry depend heavily on cold storage. Large cold rooms for preserving perishable goods (e.g., tomatoes, fish, meat) in markets like Mile 12 in Lagos or farms in Kano utilize extensive piping systems for circulating refrigerants, often at industrial scales requiring precise brazing and pipe routing.
Impact: Reduces post-harvest losses, supports food security, and enables businesses in the food supply chain.
Large Public and Commercial Buildings: Integration: Modern buildings such as airports (e.g., Murtala Muhammed International Airport), large hospitals, shopping malls, banks, and corporate headquarters across Nigeria utilize centralized air conditioning systems. These systems rely on complex ducting networks to distribute conditioned air efficiently to various zones, and extensive piping for chilled water distribution.
Impact: Provides comfortable indoor environments for occupants, critical for productivity and public health, and is a significant component of building construction and infrastructure development in Nigeria. ---