By Eamonn Ryan
In a recent ASHRAE Journal Podcast, Kelly Cramm, P.E., Life Member ASHRAE, and mechanical engineer with Henderson Engineers, shared insights drawn from more than 40 years in HVAC design and ASHRAE involvement. Cramm, who has served on numerous technical committees including TC 9.1 and 9.10, offered a comprehensive look at how VRF systems work, common pitfalls and what engineers and contractors must do to ensure long-term system success.
The following series of three articles is derived from ASHRAE Journal podcast episode 29 on the topic of ‘VRF basics and proper installation techniques’. This is part one.
VRF has faced criticism in recent years due to repeated compressor failures in the field. Cookie studio | Freepik.com
Variable refrigerant flow (VRF) systems have emerged as one of the most flexible, efficient HVAC solutions available today – especially for applications requiring precise individual zone control. But their growing popularity has also revealed a consistent theme: improper installation and maintenance are leading causes of system underperformance and premature compressor failure.
What is VRF and why does it matter?
VRF systems are all-electric, heat-pump-based HVAC solutions that can incorporate heat recovery for enhanced energy performance. They use multiple indoor fan coil units – available as ceiling cassettes, wall mounts or concealed ducted units – connected to one or more outdoor condensing units via refrigerant piping.
This configuration allows a single set of outdoor units to serve multiple indoor zones, dramatically reducing the condensing unit footprint. More importantly, VRF offers individual temperature control for each space, making it ideal for K-12 schools, offices and other multi-zone buildings.
Compared to traditional hydronic fan coil or VAV with reheat systems, VRF is often more cost-effective and simpler to install, while offering the added benefit of heat recovery between zones. Internal areas requiring cooling can reject heat that perimeter zones can reuse for heating – an elegant energy-efficient solution that reduces overall system load.
The industry challenge: compressor failures and misconceptions
Despite these advantages, VRF has faced criticism in recent years due to repeated compressor failures in the field. “Unfortunately, this issue has contributed to a negative perception in the market. Many owners have become frustrated with the need to routinely replace compressors, often without understanding the root cause,” says Cramm.
Manufacturers, eager to maintain good relationships, frequently replace failed compressors under warranty without deeper investigation. The result: systemic issues remain unaddressed, and the same installation or maintenance problems continue to cause failures.
