GM9S80 Installation Manual
15
Total external static refers to static pressure created by all
reading your total external static pressure. The supply duct
pressure must be read between the furnace and the cool-
ing coil. This reading is usually taken by removing the “A”
static reading at the test hole. Tape up the test hole after
your test is complete. The negative pressure must be read
that can cause excessive temperature rise. This can cause
limit switch tripping and heat exchanger failure.
To determine total external duct static pressure, proceed as
follows:
4.
measure the static pressure of the return duct at the
inlet of the furnace. (Negative Pressure)
5. Measure the static pressure of the supply duct. (Positive
Pressure)
6.
:
Both readings may be taken simultaneously and
read directly on the manometer if so desired. If an air
-
junction with the furnace, the readings must also include
these components, as shown in the following drawing.
7.
If the total external static pressure exceeds the maximum
listed on the furnace rating plate, check for closed dampers,
registers, undersized or poorly laid out duct work.
Digital
Manometer
-
not covered under the warranty.
installed in the central return register or a side panel external
or in the return air duct work.