AMCA InMotion - September 2019 - 29

High-Performance Air Systems vs. Other System Types
By GUS FARIS, AMCA High Performance Air Systems Committee

The following table compares in terms of key performance characteristics and capabilities high-performance air
systems (HPAS) with three other HVAC-system types:
■

Variable refrigerant flow (VRF)-typically, a group of non-ducted mini-splits with common condensing unit.

■

Chilled beam (CB)-usually, one or more chillers, an outdoor-air handler, and chilled beams, cool-water (sensible
cooling only) cooling coils built into a cabinet in which room air is blended with outdoor air before delivery to an
occupied space through a diffuser. Fan coils or series fan-powered terminal units may be required for pressurization.
The outdoor-air handler supplies all latent cooling prior to air being distributed to the chilled beams.

■

Water-source heat pump (WSHP)-self-contained packaged unit including fan, coil, and compressor usually sized
to handle a single small zone.
Performance
characteristic/
capability

HPAS VRF

CB WSHP

Comments

Comfort control

✓

Variable-air-volume terminal units ﬁne-tune airﬂow based on comfort
demands, but air-handling-unit discharge-air temperature remains
constant, ensuring a constant sensible-heat ratio and low humidity.
Engineered duct systems terminate at high-performance diffusers that
eliminate drafts and ensure proper mixing in a space.

Basic system
includes outdoor air

✓

With a HPAS, outdoor air is supplied through the duct system to each
zone. No additional duct systems or outdoor-air handlers are necessary.

Economizing

✓

HPAS can function with either water-side or air-side economizers. This
can save signiﬁcant amounts of energy with no compromise in comfort in
any climate.

Simultaneous
heating and cooling

✓

HPAS simultaneously heat and cool. In large single zones, mixing is
adequate enough to avoid reheating and recooling.

Quiet operation

✓

Centralized systems are very quiet, as their fans are located outside of occupied spaces. Additionally, there is no compressor noise in occupied spaces.

✓

With a HPAS, equipment service and maintenance usually is performed
in an equipment room or outside at the chiller. Service in local zones is
almost non-existent. There is no potential for condensation on ceilings.

Filtration

✓

With a HPAS, there is adequate ﬁltration at the air handlers. Properly
selected air-diffusion components deliver highly mixed air to zones and
provide superior comfort, meeting both ANSI/ASHRAE Standard 62.1,
Ventilation for Acceptable Indoor Air Quality, and ANSI/ASHRAE 55,
Thermal Environmental Conditions for Human Occupancy.

Refrigerant safety

✓

With a HPAS, all refrigerant is in the chiller and out of and away from
occupied spaces. Leaks are rare.

Documented
performance

✓

Performance costs of HPAS are well-documented and all-encompassing,
and system total energy use has been detailed in independent (ASHRAE/
Air Conditioning, Heating, and Refrigeration Institute) research.

Consistent
operation

✓

HPAS operate consistently through all seasons and seasonal changes.

Service and
maintenance

Gus Faris is vice president, engineering, for Nailor Industries Inc.

w w w. a m c a .o r g

20 19 A M CA i n m o t i o n

http://www.amca.org

AMCA InMotion - September 2019

Table of Contents for the Digital Edition of AMCA InMotion - September 2019