ASHRAE Journal - ACMA Supplement - Fall 2013 - 20

that a leak will produce. If smaller rooms are served by a large
system, the limits of ASHRAE 15 will be exceeded. The liability
to design professionals of hazardous refrigerant concentrations
has to be considered.
cerTified raTings

AMCA International and AHRI (The Air Conditioning, Heating
and Refrigeration Institute) certify the performance ratings of
HVAC equipment. Certified ratings require periodic check tests
and diligent review of catalog and selection programs to be
certain they are consistent with accredited third-party lab tests.
Generally, when a company chooses to certify, it changes its
ratings—from a little to a lot (more than 20%). That means that
if you accept products whose ratings are not certified, it is unlikely
that the product ratings will be in compliance with accepted
industry standards. In other words, the product may perform as
advertised, but the basis for ratings will often be different than
those who chose to certify their compliance with ANSI accredited
consensus standards that dominate the industry. This is not to
say that a noncertified product is always over-rated, but an HVAC
system designer can assure him/herself that the performance
required is indeed assured via certification. Specify that the
products used in your system (whether it’s a VAV or any other
system) are AMCA or AHRI certified. Doing anything less is

asking for trouble—and for system performance that does not
meet legitimate expectations.
TesTing The claim

First-cost comparisons come from looking at real jobs. VAV
system cost is reduced by the use of spiral ducting, taking
advantage of static regain (selecting fans on total pressure) and
low temperature air. Spiral ducting weighs 25% less and requires
30% less labor to install. For first-cost sensitive installations,
packaged rooftop equipment with high-pressure VAV capability
and fan speed control cannot be beat.
Energy cost is easier to compare using computer simulations
(Figure 1), which compare an exhaustive office building model
using energy modeling. High-performance VAV is a winner.
The BoTTom line

If air systems are done right, they will:
■
Cost 20% less than piped systems
■
Consume 20% less energy
■
Meet ventilation codes, with better control over indoor
air quality
■
Carry minimal refrigerant obsolescence and leak risk
■
Work as represented (AMCA and AHRI certified).

Annual Building Energy Use
HOUSTON
baseline rooftop VAV
VRF heat recovery
high-performance
rooftop VAV

LEGEND
Lighting
Plug Loads
Cooling
Heating
Fans

LOS ANGELES
baseline rooftop VAV
VRF heat recovery
high-performance
rooftop VAV
PHILADELPHIA
baseline rooftop VAV
VRF heat recovery
high-performance
rooftop VAV
ST. LOUIS
baseline rooftop VAV
VRF heat recovery
high-performance
rooftop VAV

2
kBtu/yr (in millions)

Figure 1. TRACE Energy model of four cities representing different climate zones and HVAC system approaches.
Courtesy: Trane/Ingersoll Rand

Fa l l 2 0 1 3

a m c a I n t e r nat I o na l

inmotion

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

http://WWW.AMCA.ORG

ASHRAE Journal - ACMA Supplement - Fall 2013

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