Premature Coil Failure in Ductless Mini-Splits & VRF Equipment - Short #303 · HVAC School - For Techs, By Techs summary

Key takeaways

Premature coil failure in ductless mini-splits and VRF systems is often caused by environmental factors like corrosion due to chlorides, salt, and chemical off-gassing.
Understanding the chemistry of corrosion, including reactions involving chlorides and galvanic processes, helps in developing effective prevention strategies.
Proper coil maintenance involves using correct cleaning procedures, thorough rinsing, and avoiding harsh chemicals that can accelerate corrosion.
Environmental control measures such as ventilation, filtration, source control, and system design modifications are critical in high-pollution or harsh environments.
Materials and system modifications, such as using aluminum coils or applying protective coatings, can extend coil life in challenging conditions.
Client education and effective communication are vital for managing expectations and implementing preventive measures.

Summary

Understanding Premature Coil Failure in Modern HVAC Systems

This section explores the main theme of coil failures, focusing on ductless mini-splits and VRF systems. The discussion covers how environmental factors such as pollution and chemical off-gassing can lead to corrosion, particularly formicary or 'ant's nest' corrosion. It emphasizes that such failures aren’t always due to manufacturing defects but often due to external conditions like salt exposure, high chloride environments, and improper maintenance. The importance of proper coil cleaning, environmental control, and understanding the chemistry behind corrosion are stressed as key to preventing premature failure.

Chemistry and Corrosion: Causes and Prevention

This section dives into the science of corrosion, particularly how chlorides from substances like bleach or cleaning agents and environmental salts promote copper coil corrosion. The conversation details reactions like galvanic corrosion and how factors like hard water minerals contribute to a buildup of corrosive compounds. Practical suggestions include using proper cleaners, rinsing coils thoroughly, and controlling indoor air quality through ventilation, filtration, and source control to dilute chlorides and other pollutants. The episode highlights that understanding the chemical interactions is crucial for effective maintenance and prevention.

Practical Strategies for Managing Coil Longevity

This section offers actionable advice for technicians and homeowners, such as using appropriate cleaners, avoiding aggressive chemicals, and installing filtration or sacrificial anodes in high-corrosion environments (like coastal areas). It stresses the importance of proper system design, environmental control, and client communication. Examples include adjusting system sizing, adding ventilation and dehumidification, and considering coil coatings or material upgrades. The episode stresses that mitigation often involves a holistic approach, considering environmental factors and system operation, rather than just replacing coils.

Show notes

In this short podcast, Bryan and Roman discuss premature coil failure in ductless mini-splits and VRF equipment.

These coils are susceptible to a few different types of corrosion. Warmer coil saturation temperatures and shorter runtimes result in lower latent capacity; whatever moisture is on the coil dries on the coil instead of draining out. Minerals and chemicals (including chlorides from bleach or cleaners) interact with the coil and may cause corrosion, including formicary ("ant's nest") corrosion. Leaks and corrosion may be environmental rather than entirely attributable to manufacturer defects.

Technicians can use proper cleaners with correct dilution ratios and rinse the coils. In situations where the environment contributes to coil corrosion, such as with substances off-gassing or dealing with coastal air, we will need to dilute the pollutants by ensuring proper ventilation. Dilution needs to be intentional, especially in hot-humid climates, and ventilating dehumidifiers with good filtration may be a good move. Source control and filtration are also good mitigation strategies, and clear, open client communication can help clients understand the problem and make informed decisions about their HVAC system.

This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, NAVAC, and Fieldpiece.

Resources

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Premature Coil Failure in Ductless Mini-Splits & VRF Equipment - Short #303