Goodmans ASX - Manual (Page 72)

SERVICING
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3. Add the two readings together.
TOTAL EXTERNAL STATIC
NOTE: Both readings may be taken simultaneously and read
directly on the manometer if so desired.
4. Consult proper table for quantity of air.
If external static pressure is being measured on a furnace to
determine airflow, supply static must be taken between the
"A" coil and the furnace.
Air Flow
TOTAL EXTERNAL STATIC
S-204 COIL STATIC PRESSURE DROP
1. Using a draft gauge (inclined manometer), connect the
positive probe underneath the coil and the negative probe
above the coil.
2. A direct reading can be taken of the static pressure drop
across the coil.
3. Consult proper table for quantity of air.
STATIC PRESSURE DROP
If the total external static pressure and/or static pressure drop
exceeds the maximum or minimum allowable statics, check
for closed dampers, dirty filters, undersized or poorly laid out
duct work.