ASHRAE Journal - June 2014 - 15

Technical FeaTure
Fea

issues as they come up, during any phase of the construction process, before moving to the next phase.
For example, FPT cannot begin until all equipment
and systems are verified to start up and function properly during pre-functional testing. So when key startuprelated items are entered into the issue log but not corrected, FPT will probably fail and need to be repeated
after the issues are corrected.
So pay careful attention to the issue log, and make sure
all issues are resolved before FPT begins.

Role of Functional Performance Testing
It's important to note that ASHRAE Guideline 0-2005
requires functional performance testing. But the
Guideline does not describe the number or type of tests to
perform, nor does it define how stringent the tests must
be or even who should conduct them. This article is an
attempt to "flesh out" the Guideline in a practical manner,
and from a technical commissioning perspective.
This article also assumes that every issue in the issue
log has been corrected, all pre-functional tests have been
verified complete and successful, all building systems and
components are properly installed and functional, and all
valves and dampers open and close as required.
At this point, you may ask, "OK, if everything is well
designed, installed correctly, and fully functional-and
all known issues have been corrected-what else is there
to do?"
This is an important question, as my experience indicates that a traditional process-commissioning CxA
would give a very different answer than would a technical-commissioning CxA. I've found that a traditional
process-commissioning CxA would likely answer:
"You're right. We've prepared the FPT forms, and the
contractors have informed us that all of their testing was
successful. We've verified that all of the commissioning forms have been completed, and we've randomly
sampled the building's equipment and systems to verify
correct installation and proper operation."
If our project employed traditional process commissioning, it would be complete; and we would be ready to
turn over the new building to its owner.
But when faced with the same question, a technical
commissioning CxA will likely answer:
"Our commissioning team has done a great job so far!
We've verified that the design satisfies the OPR. We've corrected every issue in the issue log, and we've personally

confirmed that all equipment and systems have been
properly installed and are fully functional. We're now
ready for the project's final exam: real-world, functional
performance testing of every building system. Our goal
is to ensure that the building itself (not just the design)
satisfies the OPR, so we must ensure that the occupants
find the internal environment to be efficient, healthy, and
comfortable. We've given all relevant contractors their
FPT forms, and we'll now work with them during FPT,
observing and assisting as they perform every test."
This "test-and-verify-everything" perspective is a big
difference between process commissioning and technical commissioning. Process commissioning permits
contractors to serve as their own SMEs, and allows them
to perform their own tests. However, technical commissioning requires the CxA to serve as the SME-and
as such the CXA either performs or supervises all functional performance testing.

Test Example: A Variable Air Volume Box
To illustrate how the FPT process works, this article uses
the example of a single variable air volume (VAV) box
serving a single space. But note: Proper technical commissioning requires that the CxA measure and verify the
correct operation of all control loops-not just a sample.
It is true that the CxA is permitted to perform limited
sampling during pre-functional testing (refer to the previous article in this series). But no sampling is allowed
during FPT. Instead, all systems and equipment must be
actively verified for real-world operation.
You may ask, "What's wrong with sampling? It can save
time and potentially reduce overall costs." The problem
is sampling can work well for "homogenous" systems-
such as a batch of well-mixed concrete: Every sample
taken has a high probability of having the same chemical
composition as any other sample. So if one sample meets
specifications, the rest of the batch should also meet the
specs.
But mechanical systems are never homogenous. Why?
Every system has probably been touched by multiple contracting firms and multiple technicians. Our sample VAV
box, for example, has had electrical, piping, sheet metal,
control, test-and-balance, and chemical-treatment contractors involved in its installation. Also, different employees of the same firm may build or install each of their components and systems differently. So it is likely that every
VAV box will respond differently to control inputs.
J u n e 2014

ashrae.org

ASHRAE JouRnAl

ASHRAE Journal - June 2014

Table of Contents for the Digital Edition of ASHRAE Journal - June 2014