Application Note

4 Fluke Corporation HVAC pressure applications with the Fluke 922
TSP and ESP: Total Static
Pressure (TSP) and External Static
Pressure (ESP) are used in con-
junction with the manufacturer’s
blower performance tables to
ensure that the blower perfor-
mance is sufficient to overcome
airside device pressure drops
and the pressure drop associated
with duct friction and fittings
losses. Manufacturer’s blower
performance tables will specify
whether the tables are based
on TSP or ESP. Once installed,
the TSP or ESP is measured to
select the appropriate fan RPM
that will deliver the desired cfm.
It’s important to remember that
manufacturer’s blower curves
are developed by AMCA test
procedures that do not exhibit
any system effect. Due to equip-
ment installation space and
configuration limitations, blower
performance is rarely the same
as system performance (“as-built”
rarely performs exactly “as-
designed”). Initial blower set up
is by TSP or ESP. Duct traverses
that measure actual airflow are
required for final blower set up.
TSP is normally provided for
commercial and industrial unitary
equipment. TSP includes internal
and external dynamic pressure
losses the equipment fan must
overcome. A static pickup is used
on the inlet side of the fan to
measure static pressure and the
connecting tube is connected to
the “-” port on the Fluke 922.
A static pickup is placed on the
discharge side of the blower and
the connecting tube is connected
to the “+” port on the Fluke 922.
The displayed pressure is the
TSP.
ESP is normally provided for
residential unitary equipment.
ESP is provided for equipment
that does not have optional
components that can be added
within the cabinet or when drill-
ing holes to take TSP may violate
equipment agency certifications.
The blower tables are based on
dynamic pressure losses external
to the equipment, measured at
the return opening and at the
supply opening of the unitary
equipment. Check the blower
table instructions to determine
whether or not the filter should
be in place when measuring ESP.
Place a static pickup in the return
duct at the equipment return
opening. Connect this tube to the
“-” port of the Fluke 922. Place
a static pickup in the supply
duct at the equipment discharge
opening before any external
devices such as an external
evaporator, if so equipped. Con-
nect this tube to the “+” port on
the Fluke 922. The displayed
reading will be the ESP.
FSP (P
sf
) is Fan Static Pressure
and is used to independently
rate a fan’s ability to overcome
all system dynamic pressure
losses. A Pitot tube is used on the
inlet side of the fan to measure
total pressure and the connecting
tube is connected to the “-” port
on the Fluke 922. A static pickup
is placed on the discharge side
of the blower and the connecting
tube is connected to the “+” port
on the Fluke 922. The displayed
pressure is the FSP.
Conclusion
Pressure is an often-misunder-
stood aspect of HVAC diagnos-
tics. Everyone has refrigerant
pressure gauges, but to under-
stand why “the pressures are
wrong,” you need to think about
fluid flow and heat transfer
too, instead of just adding gas
to force the pressures up. And,
while everyone probably has a
pressure gauge, it’s not always
the right kind for accurately
reading low pressure systems.
Now, with electronic meters like
the Fluke 922, you not only get
an accurate read, you can check
the actual pressure differential
instead of replacing pressure dif-
ferential switches by default.
Using the Min/Max/Avg feature
The MIN-MAX feature on
the Fluke 922, in addition
to capturing minimum and
maximum readings, will
record and average read-
ings when a fluctuating
pressure, velocity, or airflow
is encountered.
Once you’ve captured
pressure, velocity, and/or
airflow readings and stored
them in memory, they can
be recalled per selected
mode for review and
deleted individually, or as a
group.
Applications for
Min/Max/Avg include
checking:
static pressure variations
as zone dampers open
and close
CAVB bypass sizing and
damper operation
The average function is
most useful when air tur-
bulence causes minor fluc-
tuations in readings. The
average feature smoothes
out the slight variations,
making pressure evalua-
tions more accurate.
Fluke Corporation
PO Box 9090, Everett, WA USA 98206
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
For more information call:
In the U.S.A. (800) 443-5853 or
Fax (425) 446-5116
In Europe/M-East/Africa +31 (0) 40 2675 200 or
Fax +31 (0) 40 2675 222
In Canada (800)-36-FLUKE or
Fax (905) 890-6866
From other countries +1 (425) 446-5500 or
Fax +1 (425) 446-5116
Web access: http://www.fluke.com
©2006-2007 Fluke Corporation. All rights reserved.
Specifications subject to change without notice.
Printed in U.S.A. 3/2007 2817879 A-EN-N Rev B
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