HVAC and Building Controls Commissioning Experts
Why commission?
Today’s building and office
facilities are very high tech. Design engineers go through a lot of effort to
design a system that meets the needs of the customer and will perform efficiently
and with minimal maintenance. Today’s HVAC systems are also very energy
efficient. Of course all this depends on the finished product being properly
installed and then accurately tuned before the design and construction teams
leave the project.
All the good intentions will
not get the job done. When a design engineer writes a sequence of operations it
is very critical that the system operate in the order that it was designed,
otherwise energy efficiency will not conform to what was expected from the design.
Let’s look at just one critical example:
Let’s say the system design
calls for the cooling tower condenser water system to provide for “Economizer
Cooling” or free cooling at a certain outdoor air temperature and
humidity. This design option would allow
for the air distribution system to provide cooling even though the
refrigerating compressors are not running, thus saving energy and lowering
electric bills.
There are a number of things that
could jeopardize the effectiveness of this process. The sensor measuring
outdoor air temperature may not be accurate or installed in a poor location.
The sensor measuring outdoor air relative humidity could be reporting
incorrectly, out of calibration, located poorly or being effected by an
excessively long wiring run. The actual sequence of the staging of the fans off
and on and from low to high speeds may not operate correctly. If the tower fans
are variable speed, the 0-100% signal from the building control panel output
may not match the
All of these could affect the
free cooling initiation process and efficiency.
The most interesting point of
all these details is that typically, the person performing the start up and
check out will assume that the sensors are “Factory Calibrated” and don’t need
any further attention. Not true!
If a start up technician does
perform a quick check of the device to see if it is sensing accurately, what
test equipment is he using? My experience dictates he will probably use a meter
or measuring device he has on his service truck and truly does not know if it
is accurate. So now we are checking and calibrating a sensor with an inaccurate
measuring device. Not good.
The overall result is an
economizer system that comes on to soon or too late. If it comes on to soon it
is running tower fans and system pumps to attempt to reach a set point that’s
not possible under those conditions, wasting electricity for no gain. If it
comes on too late the system wastes energy by running compressors
unnecessarily.
The result to the facility is
a higher electric bill! What was mistaken as an insignificant detail could
effect your electric bill by as much as 10%. A combination of insignificant
errors could affect your electric bill by as much as 20% or more.
How much would 20% of your
electric bill equal for one month? $1,000 or even $5,000. I’ll bet you could pay for the cost of the
commissioning fees in one month!
Today’s DDC control systems
are capable of trending electric consumption along with many other useful
figures. Unfortunately, if the first months electric bill is based on an HVAC
system operating inefficiently due to a control system that does not function
up to design, the baseline numbers are now set on poor performance.
There are other reasons to
commission besides energy efficiency.
Better overall operating
comfort levels, lower maintenance costs, eliminate nuisance calls and receive a
detailed report of the results of the commissioning process. The report will
contain original settings, calibration readings, status and sequences which
will provide you with a base line for future reference.
If you are the installing
contractor effective commissioning can reduce your warranty costs substantially
by eliminating nuisance call backs during the warranty period.
With over 25 years experience
in the commercial building trade, you can count on our expertise. We can
develop a commissioning plan that is right for you.
Sachs Consulting 608