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When to Retrofit RTUs with Variable Frequency Drives (VFD)

Mar 17, 2016 6:30:00 AM


If your existing packaged rooftop air conditioning units (RTUs) meet the following criteria then a VFD Retrofit Upgrade should be considered:

  1. Existing RTUs have greater than 7 tons cooling capacity and are less than 10 years old 
  2. Existing RTUs have constant speed fan control 
  3. Existing RTUs are in good working condition with an expected additional lifetime of 5 years or more (if not consider early retirement and replacement)

The sole purpose of a VFD RTU retrofit is simple: decrease energy consumption and maintain or increase occupant comfort and environmental conditions.  

Follow these steps for a successful VFD retrofit project:

Step 1: Identify RTUs for Retrofit Application

RTU’s less than 10 years old can be given new (efficiency) life by retrofitting with a load-matching fan control technology.

Step 2: VFD Retrofit RTU

RTU is equipped with a VFD and a control interface board that matches fan speed to each RTU’s particular air flow requirements for cooling, heating and ventilating.

Step 3: Commissioning

During installation on each RTU, air flow measurements are used to determine the best air flow settings for each operation mode.



HVAC equipment typically has a lifespan of about twelve to fifteen years and that is why retrofit programs are so important. Retrofit projects replace or add equipment to existing or older systems.  They improve energy efficiency, improve energy output and extend the lifespan of the existing system.

  • Simple paybacks of less than one year.
  • Reduce total kWh usage an average of 14% per month 
  • Utility rebate programs can add an additional 10 percent cost reduction 

 Contact CES's Facility Services Team for a consultation Today:

HVAC system replacement is a costly and often tedious process that can disrupt business earnings over extended periods of time. Unfortunately, it is never a matter of if you will need your heating and cooling equipment replaced it is only a matter of when.  

Contact CES Today!

Click below to view the full JC Penny Case Study from the Department of Energy and ARC.



Comprehensive Energy Services

Written by Comprehensive Energy Services

Comprehensive Energy Services, Inc. is an award-winning, self performing provider and recognized leader in Design Build and Maintain Mechanical Contracting and Plumbing; providing a full range of advanced HVAC commercial, healthcare, and industrial services, including mechanical engineering design, mechanical construction, plumbing, IAQ, preventative maintenance and system maintenance throughout Florida.


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