TAB Journal Fall 2020 - 8

John Todd, TBE, CxA
Capital Air Balance, Inc.

Balancing
Hydronic
Pumps
with In-Line
Autoflow
Devices
We were called to re-check a chiller plant that had recently been balanced by another
company. The customer was complaining of much higher than expected energy costs.

W

e arranged for the control personnel and owner
representative to meet with us at the chiller plant.
All operating conditions were measured: flows,
amps, kilowatts, hertz, etc. The flows through the chiller,
condenser, and evaporator were found to be within acceptable
limits. We did notice that all the pumps were running at 100
percent 60 hz.
The systems - chilled water and condenser water - had
autoflow devices installed in their respective piping systems.
The autoflow installation gave us an idea that perhaps the
autoflow devices were maintaining their respective flow by
increasing the pump total dynamic head, and that the pumps
could have their respective speeds reduced.
We began to reduce the speed of the pumps gradually - with
the control personnel's assistance - from 60 hz to 45 hz on the
condenser. The flow was maintained exactly the same through
the chiller condenser bundle all the way from the 60 hz to
the 45 hz speed reduction. The exact same procedure was
followed on the evaporator side of the chiller, and the speed
was reduced from 60 hz to 40 hz while maintaining the same
evaporator flow. This was possible because the autoflow device
would open, reducing the pump head and the pump break
horsepower.

8

This reduction of the operating head greatly reduced the
kilowatts usage on the pump motors. The kilowatts were
checked before and after adjustments were made, and
witnessed by the control personnel and owner personnel.
We also started an additional cooling tower to reduce fan
operating time and speed on the tower fan. The kilowatts on
the variable frequency drives were used as the determining
factor - measured before and after adjustments were made - to
calculate the energy savings. By calculating the difference in
the kilowatt usage on the before and after usage, and by using
the customers kilowatt costs if this system ran 24/7, 365 days a
year, the owner's annual saving amounted to over $75,000.
When autof low devices are designed to establish total
f low in pumping systems, we found that it is better to start
out below the rated valve pressure drop and slowly ramp
up the pumps to the design pressure required to establish
design f low.
AIA
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TAB Journal Fall 2020

Table of Contents for the Digital Edition of TAB Journal Fall 2020

TAB Journal Fall 2020 - Cover1
TAB Journal Fall 2020 - Cover2
TAB Journal Fall 2020 - 1
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TAB Journal Fall 2020 - Cover3
TAB Journal Fall 2020 - Cover4
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