HVAC Sheet Metal Fabrication: Principles, Materials, and Design Tips

An HVAC unit’s several components work to regulate in-house air and temperature. Many of these components are metals, e.g., heat exchangers and boilers. As a result, the use of sheet metal fabrication in their manufacturing and customization.

Fabricating an HVAC part requires understanding the process principles and compatible materials. As a result, This article will discuss the principles of HVAC sheet metal fabrication, compatible materials, and some design tips so you can make an informed decision. 

What is HVAC Sheet Metal Fabrication?

HVAC sheet metal fabrication is a set of techniques tailored toward manufacturing metallic HVAC parts using sheet metals. These techniques are in four categories that include: 

• Cutting 

Cutting techniques include laser, plasma, shearing, and waterjet cutting. Each cutting technique has its unique mechanism, accuracy, and tolerance. A simple explanation for each includes: 

• Laser cutting involves using a powerful laser beam to melt and vaporize the HVAC sheet metal part, thereby cutting it. It has a high accuracy and can achieve tight tolerance. Furthermore, it is compatible with many materials and can be automated, e.gCNC laser cutting machines. Laser cutting is only ideal for thin sheet metals. 
• Shearing involves using a shear to cut the metal sheets into the desired parts. It has lower accuracy and can achieve lesser tolerance. Nevertheless, it is the best method for cutting thick sheet metal parts. 
• Plasma cutting involves using a plasma torch to heat a metal to a high temperature. This turns the heated part to plasma and cuts it. Plasma cutting is suitable for cutting thin and thick sheet metal parts.
• Water jet cutting involves cutting sheet metal parts using high-pressure water-containing abrasive materials. It is accurate and can achieve tight tolerance. Furthermore, it can cut thick sheet metals.

HVAC sheet metal cutting techniques are applicable in making HVAC ductwork, air handling unit panels, and fan blades.

• Joining 

Joining techniques include welding, riveting, and adhesives. Each has its unique mechanisms and applications.

• Welding involves using heat to join two or more sheet metal parts together. The heat melts the joint and fuses on cooling to form a strong and permanent bond. Welding techniques include laser, TIG, and MIG welding. Each one has unique features. For example, laser welding is highly accurate and suitable for thin parts. 
• Riveting involves joining two metal sheets with a rivet, a mechanical fastener inserted through a pre-drilled hole and deformed. It does not require heat, making it compatible with any sheet metal. 
• Adhesive bonding involves using an adhesive material to join two parts together. It does not use heat but is only suitable for lightweight HVAC parts not exposed to fluids.
• Bending

Bending is an HVAC sheet metal fabrication that involves bending a sheet metal at an angle with a press machine into the desired shapes. You can also bend into cylindrical or curved shapes using a roller.  The sheet metal fabrication technique can make HVAC duct elbows, transitions, and fittings.

• Forming

Two forming techniques suitable for fabricating HVAC parts are stamping and deep drawing. On the one hand, stamping involves using a die and punch set to deform the metal sheets. On the other hand, deep drawing involves pulling a metal sheet through a die cavity with a punch to form a hollow shape.

The forming techniques can make HVAC parts like fan housings, compressor casings, and heat exchanger plates.

Materials for HVAC

There are many materials applicable in making materials for HVAC parts. Each one has unique properties that make them applicable differently. Below are a few materials and their properties.

• Ordinary thin steel plate

Ordinary thin steel plates have moderate strength, good formability, and weldability. They are applicable in making HVAC parts such as ductwork, air handling unit components, and enclosures. Disadvantages of using the sheet metal alloy include corrosion in harsh environments. As a result, they might need to undergo surface treatments to improve corrosion resistance.

• Galvanized thin steel plate

This is an ordinary steel plate coated with a thin layer of zinc using a hot dip galvanization. Aside from the moderate strength, formability, and weldability, the sheet metal part has better corrosion resistance. 

The material is suitable for making duct works, air ducts, and other HVAC parts that should be corrosion-resistant. A disadvantage of the material is the degradation of the zinc coating over time and the production of toxic fumes during welding. 

• Stainless steel plate

Stainless steel is a common HVAC material with high corrosion resistance, strength-to-weight ratio, and heat resistance. It is the best material for HVAC parts exposed to harsh conditions such as heat and chemicals. 

Examples of HVAC parts made with stainless plates are heat exchangers. A disadvantage of the material is the need for expertise during welding and other fabrication processes.

• Electro-galvanized sheet

This is a sheet metal subjected to electrogalvanization. It involves immersing the parent material in a bath solution containing zinc salts. Passing an electric current through the bath leads to the deposition of a thin layer of zinc on the surface.  

The zinc coating improves the parent material’s corrosion resistance and durability. As a result, they are a good option in making HVAC parts like enclosures and ductwork.

Some drawbacks of using the materials include susceptibility to scratching and damage during fabrication. Furthermore, it has lower corrosion resistance than hot-dipped galvanized sheets due to the thinner zinc coat. 

• Color-coated steel plate

Color-coated steel plates are more for aesthetic purposes. However, they might be functional, e.g., painting can improve corrosion resistance. You can make the steel plate using painting and chromate conversion zinc coating on the parent metal. 

Use color-coated steel plates to fabricate HVAC enclosures and cabinets. Disadvantages of using them include scratching and chipping, which degrade the protective elements. Furthermore, there are fewer color options. 

• Hot-rolled plates and cold-rolled plates

Hot rolled sheet metals have a rough surface finish and lesser tolerance. Hence, they are a good option for making structural HVAC components. On the other hand, cold rolled plates have a smoother surface finish and tighter tolerance. Hence, they are applicable in precision HVAC parts.

The disadvantages of hot-rolled plates are residual stresses and surface imperfections while cold-rolled plates are expensive.  

• Highly corrosion-resistant steel plates

These steel plates incorporate chromium, nickel, and molybdenum at a higher percentage composition. As a result, they have improved corrosion resistance and pitting resistance. 

They are the best material for HVAC components used in harsh environments. An example is the marine industry. Drawbacks of the material include its limited availability and the need for higher fabrication experience.

• Zinc-aluminum alloys

Zinc aluminum alloy plates contain zinc and aluminum. As a result, they have better corrosion resistance and mechanical properties. They are suitable for making outdoor HVAC parts such as roofing systems and structural supports. 

Disadvantages of the material include a high cost and limited availability, formability, and welding.

• Zinc-aluminum-magnesium rare earth

The presence of zinc, aluminum, magnesium, and other rare earth elements improves the sheet metal’s corrosion resistance and strength. Hence, it can make high-performance HVAC components like heat exchangers, dumpers, and combustion chambers. 

The disadvantages of the metals are their high cost and the need for specialized fabrication and welding processes.

Choosing a material involves understanding the material’s properties and the point of use. However, with experience from reputable HVAC sheet metal fabrication service providers like Zintillon, you can choose the best material for your HVAC component.

Design Tips for HVAC Sheet Metal Fabrication

Designing Tips for HVAC sheet metal fabrication encompasses different niches and considers several factors. Your design depends on the following: 

• Meeting Indoor Environment Requirements

Know the indoor environment requirements to fabricate HVAC components with the right dimensions. Furthermore, this knowledge will help you meet the quality standards in the industry.

• Load Calculation

A load calculation will determine the HVAC unit size and capacity, which then translates to the size and capacity of the HVAC components. You can calculate the load by considering the building size, occupancy, heat gain, and climate.  

• Airflow Organization

The HVAC ductwork design should minimize air resistance and pressure drop and optimize airflow distribution. You can achieve this with smooth transitions, gradual bends, and duct sections.

• System Efficiency

Choose cheap and durable materials to reduce production and maintenance costs. Furthermore, you can reduce the material used with demand-based ventilation strategies to improve operational efficiency.

• Energy Conservation and Sustainability

Using recycled and sustainable materials for HVAC sheet metal fabrication will reduce environmental impact. The design systems should have energy-recovery ventilators and high-efficiency filters.

• Noise Control

Use sound-absorbing materials and insulation in fabricating HVAC enclosures and ductwork to reduce noise. Furthermore, an HVAC duct design that encourages minimal airflow turbulence velocity will reduce noise. 

• Safety and Health

The material chosen and the fabricated HVAC part should comply with safety regulations and industry standards. For example, HVAC part manufacturers should not use materials associated with VOC emissions or coating that can emit toxic fumes.

• Maintenance and Operation

The designed HVAC part should aid accessibility after assembly for easier maintenance and service. This is achievable with clear labeling and documentation.

• Policy Compliance: ASHRAE & NEC

During HVAC part design and fabrication stages, comply with industrial policies from standards like ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) and NEC (National Electrical Code).

• Flexibility and Scalability

Design a flexible and scalable HVAC unit that can accommodate future changes or expansions in the build. Using prefabricated assemblies will facilitate faster reconfiguration or expansion. 

Conclusion

Sheet metal fabrication is applicable in the manufacturing and customization of HVAC unit components. This article discussed the principles of HVAC sheet metal fabrication, compatible materials, and some design tips so you can make an informed decision.