2. A double riser discharge line may be used as shown
in Figure 12, Page 9. Line “A” should be sized
to carry the oil at minimum load condition and line
should be sized so that at the full load con-
dition both lines would carry oil.
The above two points are particularly important in
applications where the refrigerant receiver is directly
beneath the air cooled condensers. If two unlike air
cooled condensers or unequal piping is used, the re-
sultant unequal refrigerant pressure drop may cause
liquid to build up in one of the condenser coils, there-
by reducing its effective capacity.
Notice in all illustrations, the hot gas line is loop-
ed at the bottom and top of the vertical run. This is
done to prevent oil and condensed refrigerant from
flowing back into the compressor and causing damage
The highest point in the discharge line should always
be above the highest point in the condenser coi I; and
it is advisable to include a purging vent at this point
to release noncondensibles from the system.
Figure No. 13, below, i I I us t ra te s another very
common application where the air cooled condenser is
located on essentially the same level as the compress-
FIGURE NO. 11
PURGE
V A L V E
DISCHARGE LINE
HECK VALVE
LIQUID LINE
FIGURE NO. 13
DISCHARGE LINE
I
TO EVAPORATOR
R E C E I V E R
or and receiver. The discharge line piping in this
case is not too critical. The principal problem en-
countered with this arrangement is that there is fre-
quently insufficient vertical distance to allow free
drainage of liquid refrigerant from the condenser coil
to the receiver.
To guard against gas binding in the receiver and
liquid buildup in the condenser coil, which are com-
mon to this arrangement, be certain that the receiver
is located as far below the condenser outlet as pos-
sible. The liquid line should be free of any traps or
loops and, if there are any horizontal runs, they
should be pitched down toward the receiver.
F i g u r e N o . 1 4 , b e l o w , i l l u s t r a t e s a t h i r d v e r y
common application where two or more separate air
cooled condensers are piped together on a single
compressor.
First of all, it is very important that the two air
cooled condensers have the same capacity so that the
refrigerant pressure drop through each unit is equal.
Secondly, the piping should be arranged so that the
lengths of run to and from each air cooled condenser
are equal.
FIGURE NO. 12
PURGE
V A L V E
LIQUID LINE
FIGURE NO. 14
PURGE
V A L V E
I
I I I
CONDENSER CONDENSER
\
EVAPORATOR
C H E C K V A L V E \
Page 9
