ASPT Service Manual

Table Of Contents
SERVICING
100
Refrigerant Piping
The piping of a refrigeration system is very important in
relation to system capacity, proper oil return to compressor,
pumping rate of compressor and cooling performance of
the evaporator.
POE oils maintain a consistent viscosity over a large
temperature range which aids in the oil return to the
compressor; however, there will be some installations
which require oil return traps. These installations should
be avoided whenever possible, as adding oil traps to the
refrigerant lines also increases the opportunity for debris
and moisture to be introduced into the system. Avoid long
running traps in horizontal suction line.
Duct Static Pressures
This minimum and maximum allowable duct static pressure
for the indoor sections are found in the specications
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
insu󰀩cient air that can cause icing of the coil. Too much
air can cause poor humidity control and condensate to be
pulled o󰀨 the evaporator coil causing condensate leakage.
Too much air can also cause motor overloading and in
many cases this constitutes a poorly designed system.
Single Piece Air Handler External Static
To determine proper airow, proceed as follows:
1. Using a Inclined Manometer or Magnehelic gauge ,
measure the static pressure of the return duct at the inlet
of the air handler, this will be a negative pressure (for
example-.30”wc)
2. Measure the static pressure of the supply duct at the outlet
of the air handler, this should be a positive pressure (for
example .20”wc).
3. Add the two readings together (for example -.30”wc +
.20”wc = .50”wc total external static pressure.
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read directly on the manometer if so desired.
4. Consult proper air handler airow chart for quantity of air
(CFM) at the measured external static pressure.
Two Piece Air Handler External Static Pressure
To determine proper airow, proceed as follows:
1. Using a Inclined Manometer or Magnehelic gauge,
measure the static pressure between the outlet of the
evaporator coil and the inlet of the air handler, this will be
a negative pressure ( for example -.30”wc)
2. Measure the static pressure of the supply duct at the
outlet of the unit, this should be a positive pressure (for
example .20”wc).
3. Add the two readings together (for example -.30”wc +
.20”wc = .50”wc total static pressure.

read directly on the manometer if so desired.
4. Consult proper air handler airow chart for quantity of air
(CFM) at the measured external static pressure.