OEM vs Aftermarket HVAC Parts

OEM stands for Original Equipment Manufacturer, so these parts are the same brand as the ones who originally created it. These parts are intended to work with the same brand equipment and are designed to original engineering tolerances, materials, and performance specs of the unit. Because of this, OEM parts are often serialized or revision-controlled to match specific models or serial ranges.

Aftermarket parts are parts made by third-party manufacturers and are intended to function across multiple OEM models. These are not brand specific. This means their specs may be equivalent rather than identical. Due to the different qualities of both, there are certain situations in which it would be better to use OEM over aftermarket parts, and vice versa. Let’s break them down.

When To Use OEM HVAC Parts?

• Warranty: If the equipment is still under active OEM warranty, you’ll want to use OEM parts. Many manufacturers specify OEM-only replacement parts for preservation of the warranty. For example, Condair states that use of a non-Condair manufactured humidifier cylinder will void the warranty of the entire product. If the HVAC unit is under warranty, it’s best practice to use OEM parts to maintain coverage.
  
  
• Proprietary: If the component is proprietary or software-driven, only use OEM replacement parts. These parts are control-critical and rely on specific system logic and firmware that is intellectual property of the original manufacturer. As aftermarket parts may not have identical specs, functionality could be affected. Examples of these types of parts include control boards, communicating system components, VFDs with OEM firmware, and OEM-specific sensors with calibration dependencies.
  
  
• Safety & Compliance: Many components are critical to the safe operation of the unit, and therefore have certain specs that must be adhered to. Some of these parts include gas safety valves, ignition and flame safety devices, and heat exchangers. When it comes to safety, using OEM replacement parts is the best way to ensure accurate specs and therefore optimal safety performance. In addition, some facilities may require OEM documentation in order to maintain their compliance certification. This is common in critical facilities like healthcare, senior living, and data centers which must prioritize compliance and risk reduction.

When Can You Use Aftermarket HVAC Parts?

• Out of Warranty: Once you no longer have to worry about voiding your equipment warranty by using a non-OEM part, the risk shifts to functional performance, reliability, and downtime avoidance. Use of aftermarket parts is common in legacy RTUs, aging split systems, or discontinued model lines that have limited OEM support. As long as the specs are equivalent, aftermarket parts can be a viable option.
  
  
• Industry-Standard & Non-Proprietary: Aftermarket parts are acceptable to use if they do not alter system logic or performance algorithms. In the event of mechanical failure, these are parts that are governed by industry standards rather than OEM intellectual property. Again, the key is to ensure they have corresponding specs. Here are some common components that can be aftermarket, along with any necessary matching specs:
  
  
  • Capacitors (matching µF rating (microfarad or MFD))
  • Contactors & Relays
  • Belts, Bearings & Pulleys
  • Fan Blades (matching diameter, pitch, rotation)
  • Universal motors (matching HP, RPM, voltage, frame rotation)
    
    
• Availability & Cost: Oftentimes during peak heating or cooling season, OEM parts will be in high demand and therefore have lengthy lead times. In the event of an emergency or extended downtime, aftermarket parts can be more readily obtained. In the event of mechanical repairs on out-of-warranty equipment, service managers can determine if the impact of downtime exceeds brand preference, and if so, aftermarket can be an acceptable option. They’re also often cheaper. Aftermarket HVAC parts can be 15-40% lower cost than OEM counterparts, particularly for mechanical components like motors.
  
  
• Critical Parameters Match: HVAC parts that are sourced by a third-party manufacturer may seem identical to OEM parts, but this is not always the case. If aftermarket parts fit the necessary conditions (out of warranty, non-propriety, etc.), it’s important to verify manufacturer cross-reference and ensure matching parameters on the following before purchase:
  
  
  • Electrical ratings (voltage, phase, FLA, locked-rotor amps)
  • Mechanical dimensions (shaft diameter/length, mounting)
  • Performance characteristics (motor RPM, torque curve, airflow impact)
  • Environmental ratings (temperature, moisture, vibration)

OEM Parts vs Aftermarket Parts Rule of Thumb

• Mechanical & electrical components – Aftermarket usually acceptable if out of warranty.
• Controls, logic, safety, and communication components – OEM preferred.
• Downtime emergency – Aftermarket often justified if specs match.
• Warranty-active equipment – OEM only unless manufacturer allows equivalency.

Aftermarket HVAC parts are not inherently worse than OEM parts, but there is a specific time and place for them. It’s important to consider the full scope of your situation, including cost, availability, warranty status, impact to downtime, and function when deciding whether to use OEM or aftermarket HVAC parts. If you’re still unsure which route is best for your HVAC equipment needs, contact our parts pros today!