TAB Journal Fall 2015 - 8

TERMINAL BOX DDC
CONTROLS STARTUP

Guy W. Griffin, TBE
Engineered Air Balance Co., Inc.

TERMINAL INLET

MULTIPOINT
VELOCITY
PRESSURE
SENSOR

DAMPER
SHAFT

The startup of DDC-controlled terminal boxes by the controls contractor can make
the test and balancing of a system go very smoothly if done by an experienced
and detail-minded control technician. On the other hand if the control technician
is inexperienced and has not been properly trained or is a seasoned veteran who
just doesn't care to perform to a high standard, the job can be very challenging.
On a recent test and balancing project of a hospital addition,
the control technician was very inexperienced and was not
given the support and training he needed prior to performing
the startup of the terminal boxes. The first box that was
balanced had the following problems; damper rotating
backwards, heating water valve rotating backwards, cap
missing on the high port of the velocity sensor test ports
and the DDC controls indicating zero airflow. After finding
similar issues with the next few boxes it was determined that
the all of the boxes on the floor had the dampers and heating

8

water valve actuators rotating backwards.
When testing and balancing VAV systems it is imperative that
the balancing technician thoroughly troubleshoot the box prior
to moving on, so all the deficiencies can be identified. When
a job is not performed correctly by the mechanical or controls
contractor it is the balancing technician's obligation to the
owner to identify why the system is not operating correctly and
performing to the engineer's specifications.
Above is a diagram of a terminal inlet noting the Multipoint
Velocity Pressure Sensor and the damper shaft.

TAB Journal Fall 2015



Table of Contents for the Digital Edition of TAB Journal Fall 2015

TAB Journal Fall 2015

https://www.nxtbook.com/ygsreprints/AABC/G118248AABC_Spring2020
https://www.nxtbook.com/ygsreprints/AABC/G116302AABC_Winter2020
https://www.nxtbook.com/ygsreprints/AABC/G114573_AABC_Fall2019
https://www.nxtbook.com/ygsreprints/AABC/G111085_tab_summer2019
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https://www.nxtbook.com/ygsreprints/AABC/g104992_tab_winter2019
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https://www.nxtbook.com/ygsreprints/AABC/g94804_tab_spring2018
https://www.nxtbook.com/ygsreprints/AABC/g91043_tab_winter2018
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https://www.nxtbook.com/ygsreprints/AABC/g81312_tab_summer17
https://www.nxtbook.com/ygsreprints/AABC/g78003_tab_spring17
https://www.nxtbook.com/ygsreprints/AABC/g73432_tab_winter17
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