Thomas Denoi Basic Refrigeration Circuit April 30, 2023, 2:14 pm - HVAC School

Search In:

Event Videos Tech Tips Apps Books Podcasts Users

HVAC Feed
Resources
Content
Courses
Events
Jobs
- Create a Job Post
- Job Posts
Shop
Partners

Search In:

Event Videos Tech Tips Apps Books Podcasts Users

+

Chinese (Simplified)

Get Tech Tips

Subscribe to free tech tips.

BACK

Thomas Denoi Basic Refrigeration Circuit April 30, 2023, 2:14 pm

April 30, 2023

Print Friendly, PDF & Email

Share this Tech Tip:

Check out our most recent video

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

Audio Player

Why VRF Compressors Die w/ Roman

HVAC School – For Techs, By Techs

Why VRF Compressors Die w/ Roman

In this episode, Bryan and Roman dive deep into the world of Variable Refrigerant Flow (VRF) systems, focusing on the persistent issue of compressor failures.[...]

0.8
1
1.2
1.5
2

Facebook
Twitter
Linkedin
Copy episode link Copied
Download

00:00

56:52

Why VRF Compressors Die w/ Roman

byBryan Orr

In this episode, Bryan and Roman dive deep into the world of Variable Refrigerant Flow (VRF) systems, focusing on the persistent issue of compressor failures. VRF technology has evolved, and it has seen a major rise in the North American market since the early 2010s. Roman shares his passion for VRF, tracing its origins back to 1982 and explaining how it earned the nickname “chiller killer” by replacing traditional chiller systems in large facilities like hotels, churches, and schools. However, with this rapid adoption came a troubling reputation: VRF systems became notorious for frequent compressor failures, prompting some institutions to revert to older technologies.

There are three primary causes of compressor failure in VRF systems: oil lubrication issues, liquid refrigerant return, and electrical failures. VRF compressors are shipped with excess oil to account for the system’s extensive piping and multiple indoor units, but improper refrigerant charge—either overcharging or undercharging—can disrupt oil return and lead to gradual compressor death. They emphasize the importance of correct installation, accurate charge calculation, and diligent maintenance. Bryan adds that measuring discharge superheat is a key diagnostic tool: high discharge superheat with normal suction superheat signals poor lubrication and impending failure.

The discussion then shifts to the dangers of liquid refrigerant returning to the compressor. Even small amounts can wash oil off the scroll plates, leading to metal-on-metal contact, galling, and eventual mechanical breakdown. Roman details the difference between high-pressure shell and low-pressure shell compressors, noting that VRF systems are more susceptible to operational flood back, which can cause elevated amp draws and catastrophic failure. They also highlight the role of contamination—such as copper shavings or sand from installation—which can damage expansion valves and lead to chronic flood back issues. Maintenance, including regular oil analysis and monitoring of expansion valve performance, is crucial for long-term reliability.

Finally, the episode covers electrical failures, often the result of underlying mechanical issues rather than true electrical faults. The hosts advocate for using insulation resistance testing (megohmmeters) as a maintenance tool to track winding degradation over time. They stress that proper cleanup after a compressor failure is vital, recommending temporary filter dryers and oil analysis to mitigate contamination. The conversation closes with practical advice: always investigate the root cause of a compressor failure, communicate findings with clients, and prioritize best practices in installation and service to prevent repeat issues.

Topics Covered in This Episode:

The history and rise of VRF technology in North America
Why VRF systems earned the nickname “chiller killer”
The three primary causes of VRF compressor failure:
- Oil lubrication issues (overcharge/undercharge, oil return)
- Liquid refrigerant return (flood back, expansion valve failures)
- Electrical failures (mechanical causes, insulation degradation)
Diagnostic techniques: discharge superheat, suction superheat, amp draw analysis
The impact of installation practices and system contamination
Maintenance best practices: oil analysis, filter dryers, insulation resistance testing
The importance of root cause analysis after compressor failures
Resources for ongoing VRF education: VRF Tech Talk podcast, Facebook group, and Roman’s YouTube channel

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

Subscribe to our YouTube channel.

Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android

Search Episodes

Why VRF Compressors Die w/ Roman

06/05/2025

Bryan Orr

No Serve Situations – Short #243

06/03/2025

Bryan Orr

Locked Compressor Mistakes w/ Bert

05/29/2025

Bryan Orr

When 0V Isn’t Safe – Short #242

05/27/2025

Bryan Orr

Compressor Ohm Mistakes w/ Bert

05/22/2025

Bryan Orr

Motor Ambient Rating – Short #241

05/20/2025

Bryan Orr

Superheat Talk w/ JD Kelly

05/15/2025

Bryan Orr

How to Deal w/ Too Much – Short #240

05/13/2025

Bryan Orr

Delta T Talk w/ JD Kelly

05/08/2025

Bryan Orr

Fire Sprinklers – Short #239

05/06/2025

Bryan Orr

Search Results placeholder

Check our latest Tech Tips

Checking Disconnects 5 Capacitor Facts You Should Know Discovering Mental Reference Points

Nylog Blue Gasket -Thread Sealant for AC/R Systems

<strong>Nylog Blue Gasket -Thread Sealant for AC/R Systems</strong><br> One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER

<strong>VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER</strong><br> Venom Pack Condenser Cleaner is a high foaming pure concentrate liquid designed to tackle the toughest soils. The proprietary blend of specialty detergents will liquify heavily embedded grease and grime to restore heat transfer and increase the efficiency of the coil.

Viper Condensate Pan and Drain Treatment

<strong>Viper Condensate Pan and Drain Treatment</strong><br> Viper Condensate Pan and Drain Treatment is a sprayable gel. It coats the pan, p-trap and drain piping with a lubricative film to improve flow and prevent future soil adhesion. The slow dissolving enzyme gel will outperform and outlast conventional tablets and strips.

Nylog Blue Gasket -Thread Sealant for AC/R Systems

<strong>Nylog Blue Gasket -Thread Sealant for AC/R Systems</strong><br> One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER

<strong>VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER</strong><br> Venom Pack Condenser Cleaner is a high foaming pure concentrate liquid designed to tackle the toughest soils. The proprietary blend of specialty detergents will liquify heavily embedded grease and grime to restore heat transfer and increase the efficiency of the coil.

Viper Condensate Pan and Drain Treatment

<strong>Viper Condensate Pan and Drain Treatment</strong><br> Viper Condensate Pan and Drain Treatment is a sprayable gel. It coats the pan, p-trap and drain piping with a lubricative film to improve flow and prevent future soil adhesion. The slow dissolving enzyme gel will outperform and outlast conventional tablets and strips.

Nylog Blue Gasket -Thread Sealant for AC/R Systems

<strong>Nylog Blue Gasket -Thread Sealant for AC/R Systems</strong><br> One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

NAVAC

FROM AUGUST 2024 TO MARCH 2025 BUY NAVAC TOOLS FOR A CHANCE TO WIN A MOTORCYCLE! Any purchase of NAVAC HVAC Tools is eligible to gain entries for a Grand Prize of a Harley Davidson motorcycle.

NAVAC

Find out more about the Innovative <strong>NAVAC</strong> line of Vacuum Pumps

NAVAC

FROM AUGUST 2024 TO MARCH 2025 BUY NAVAC TOOLS FOR A CHANCE TO WIN A MOTORCYCLE! Any purchase of NAVAC HVAC Tools is eligible to gain entries for a Grand Prize of a Harley Davidson motorcycle.

NAVAC

Find out more about the Innovative <strong>NAVAC</strong> line of Vacuum Pumps

NAVAC

FROM AUGUST 2024 TO MARCH 2025 BUY NAVAC TOOLS FOR A CHANCE TO WIN A MOTORCYCLE! Any purchase of NAVAC HVAC Tools is eligible to gain entries for a Grand Prize of a Harley Davidson motorcycle.

Comments

To leave a comment, you need to log in.

Related Tech Tips

Old Books Read more

History of Thermometry and the Invention of Thermometers Read more

Defrost Time & Temperature Read more

loading

To continue you need to agree to our terms.

Terms and Conditions

The HVAC School site, podcast and tech tips
made possible by generous support from

Interested in a HVAC Career?

Find A local trade school

Resources

Calculators
Tool list
Apps
Great Books
Software and Business
Other Resources we like
Unconformed

Content

Start
Podcasts
Videos
Social Media
Tech Tips
Quizzes
Courses

Events

6th Annual HVAC/R Training Symposium
Upcoming Events
Create an Event
Event Partnership

Jobs

Job Posts
Create a Job Post

Partners

Partners
Carrier
Copeland (Emerson)
Fieldpiece
NAVAC
Refrigeration Technologies
Santa Fe

Get Tech Tips

Subscribe to free tech tips

Email Address

First Name

Terms and conditions & Privacy Policy
EULA
Reuse License

©2025 - HVAC School | All rights reserved