WSHP System Control and Optimization Part 6: Retrofit Projects Demonstrate Real World Success

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By Chad Edmondson

In this series we’ve made strong case for designing multi-unit WSHP systems for commercial and institutional facilities. By incorporating the design strategies discussed in this series you can have the best WSHP system. The indisputable advantages include:

  • Lower first cost when compared to conventional WSHP designs and many other HVAC system types

  • Lower lifetime energy cost (25% or more reduction over conventional systems)

  • Potential elimination or reduction in size of the dedicated outdoor air system (DOAS)

  • Improved indoor air quality and comfort due to elimination of humidity issues

  • Longer equipment life

  • Simpler maintenance

But what about existing systems? Do the same advantages apply in a retrofit situation when the existing system is approaching end-of-life?

The answer is YES!

School WSHP Retrofits Lower Energy Usage by 25%!

We’ve supplied equipment for many successful WSHP retrofits, including schools which typically face the most restrictive budgets. This solution has produced transformative success in schools in three separate South Carolina counties, Richland, Aiken and Pickens.

Pickens County Schools, in particular, demonstrates the real world potential of a schoolwide WSHP retrofit. Three of the four schools in this district, Forest Acres Elementary, Six Mile Elementary and Getty Middle School, all faced very similar challenges. All of the schools had existing systems with air-cooled chillers and 2-pipe fan coil units in each classroom. Outdoor air was introduced to the spaces through the wall-mounted fan coils, as there were no central dedicated outdoor air units (DOAS) in any of the schools.

It was determined that the existing piping was suitable for condenser water distribution to WSHPs and so the system was retrofitted using WSHPs with modulating hot water reheat. This feature, marketed as ClimaDry® by ClimateMaster, allows for dehumidification of the air by first overcooling it and then reheating it to an appropriate supply temperature via a modulating reheat coil. The retrofitted systems not only eliminated the humidity issues the schools were encountering, but also reduced energy consumption by 25% in all three schools without the addition of any DOASs.

South Carolina schools achieve significant energy reduction after undergoing complete HVAC retrofits using water source heat pumps (WSHP).

Pickens Elementary School was somewhat unique in that it had an existing outdated WSHP system that included large console units in each classroom. It was experiencing excessive humidity. The new design incorporated space saving vertical WSHP units. These units were small enough to be installed in closets that were built in the corner of each classroom and were specified with side air distribution because there was not sufficient ceiling space to run ductwork. Like the previous retrofits, the vertical units were equipped with modulating hot water reheat, which resolved all of the humidity issues without the addition of a DOAS.

These are four real world examples of school HVAC retrofits using a multi-unit WSHP design. Each school was facing specific challenges with the existing system, but across the board all of the schools saw vast improvements in comfort and efficiency when the retrofit was complete.