Static Pressure Drop Across Coils; Air Handler External Static - Goodman ASX Service Instructions Manual

SERVICING
Oil Trap Construction
45 °
Ell
Short Radius
Street Ell
Fig 7. Oil Trap
4. Low voltage wiring. Verify low voltage wiring size
is adequate for the length used since it will be
increased in a long line application.
System Charging
R-410A condensers are factory charged for 15 feet of line set.
To calculate the amount of extra refrigerant (in ounces)
needed for a line set over 15 feet, multiply the additional
length of line set by 0.6 ounces. Note for the following
formula, the linear feet of line set is the actual length of liquid
line (or suction line, since both should be equal) used, not the
equivalent length calculated for the suction line.
Extra refrigerant needed =
(Linear feet of line set – 15 ft.) x X oz./ft.
Where X = 0.6 for 3/8" liquid tubing
Remember, for condensers with a liquid valve connection
less than 3/8" diameter, 3/8" liquid tubing is required for a
line set longer than 25 feet.
Follow the charging procedures in the outdoor unit I/O
manual to ensure proper superheat and sub-cooling levels,
especially on a system with a TXV installed in the indoor unit.
Heat pumps should be checked in both heating and cooling
mode for proper charge level. This guideline is meant to
provide installation instructions based on most common long
line set applications. Installation variables may affect sys-
tem operation.
NO ADDITIONAL COMPRESSOR OIL IS NEEDED FOR
LONG LINE SET APPLICATIONS ON RESIDENTIAL SPLIT
SYSTEMS.
60
Long Radius Street Ell
45°
Street
Ell
S-202 DUCT STATIC PRESSURES AND/OR
STATIC PRESSURE DROP
ACROSS COILS
This minimum and maximum allowable duct static pressure
for the indoor sections are found in the specifications section.
Tables are also provided for each coil, listing quantity of air
(CFM) versus static pressure drop across the coil.
Too great an external static pressure will result in insufficient
air that can cause icing of the coil. Too much air can cause
poor humidity control and condensate to be pulled off the
evaporator coil causing condensate leakage. Too much air
can also cause motor overloading and in many cases this
constitutes a poorly designed system.
S-203 AIR HANDLER EXTERNAL STATIC
To determine proper air movement, proceed as follows:
1. Using a draft gauge (inclined manometer), measure the
static pressure of the return duct at the inlet of the unit,
(Negative Pressure).
2. Measure the static pressure of the supply duct, (Positive
Pressure).
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.