York HA090 Technical Manual page 119

036-21328-003-D-0206
LINE SIZING
When sizing refrigerant pipe for a split-system air conditioner,
check the following:
1. Suction line pressure drop due to friction.
2. Liquid line pressure drop due to friction.
3. Suction line velocity for oil return.
4. Liquid line pressure drop due to vertical rise.
Tables 6 and 7 list friction losses for both the suction and liq-
uid lines on the condensing section. For certain piping
arrangements, different sizes of suction line pipe may have to
be used. The velocity of the refrigerant vapor must always be
great enough to carry the oil back to the compressor.
Evaporator Below Condensing Section - On a split system
where the evaporator blower is located below the condensing
section, the suction line must be sized for both pressure drop
and for oil return. Oil traps may be required on this type of
application. See Table 6.
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Condensing Section Below Evaporator - When the con-
densing section is located below the evaporator blower, the
liquid line must be designed for the pressure drop due to both
friction loss and vertical rise. See Table 7. I f the pressure
drop due to vertical rise and friction exceeds 40 psi, some
refrigerant will flash before it reaches the thermal expansion
valve.
Flash Gas:
1. I ncreases the liquid line pressure loss due to friction
which in turn causes further flashing.
2. Reduces the capacity of the refrigerant control device
which starves the evaporator.
3. Erodes the seat of the refrigerant control device.
4. Causes erratic control of the refrigerant entering the
evaporator. (See I nstallation I nstructions for more detail.)
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