How Do I Know if My RTUs are Efficient? When do I Replace or Retrofit Them?

December 2, 2015

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Advanced RTU Campaign: Decision Tree for RTU Replacements or Retrofits.

Advanced RTU Campaign: Decision Tree for RTU Replacements or Retrofits.

By Marta Schantz
This is the second in a blog series on DOE’s Advanced Rooftop Unit Campaign.

Because roof top unit (RTU) air conditioners have such long useful lifetimes, building owners/managers don’t always know the best way to optimize them. The Advanced RTU Campaign offers an Evaluation Methodology that ranges from an initial RTU inventory through analysis, procurement, and M&V.

Do you replace the unit? Do you retrofit with advanced controllers? Do you improve your maintenance practices? The Campaign published a handy Decision Tree to answer those questions and identify next steps to make actionable decisions for RTU efficiency across a portfolio.

In general, existing RTUs are good candidates for retrofit with advanced controllers when they:

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

JCPenney retrofitted over 1,000 RTUs with advanced controller variable frequency drives (VFDs), and achieved energy savings of over 47,000,000 kWh, a 22% reduction from before the VFD retrofit and a monetary savings of about $5 million. Learn more in their case study here.

RTUs are good candidates for replacement with high-efficiency units when:

  • they are more than 10 years old
  • they are in poor operating condition and require expensive repairs
  • improved humidity and comfort control of the building is required
  • the building is undergoing a comprehensive retrofit
  • they use R22 refrigerant

Recently, adidas instituted a planned RTU replacement program to replace their units with high-efficiency CEE Tier II models. The resulting benefits range from reduced utility spend and avoided maintenance cost, to an improved consumer experience by reducing equipment failure.  Learn more in their case study here

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