AAON RL-240 - Manual (Page 47)

47
Adjusting Sub-cooling and Superheat
Temperatures
The system is overcharged if the sub-cooling
temperature is too high and the evaporator is
fully loaded (low loads on the evaporator
result in increased sub-cooling) and the
evaporator
superheat is within the
temperature range as shown in the table
above (high superheat results in increased
sub-cooling).
Correct an overcharged system by reducing
the amount of refrigerant in the system to
lower the sub-cooling.
The system is undercharged if the superheat
is too high and the sub-cooling is too low.
Correct an undercharged system by adding
refrigerant to the system to reduce superheat
and raise sub-cooling.
If the sub-cooling is correct and the
superheat is too high, the TXV may need
adjustment to correct the superheat.
Refrigerant Filter Driers
Each
refrigerant circuit contains a
replaceable core filter drier. Replacement is
recommended when there is excessive
pressure drop across the assembly or
moisture is indicated in a liquid line sight
glass.
Table 13 - Filter Drier Maximum Pressure Drop
Circuit Loading Max Pressure Drop
100% 5 psig
50% 2.5 psig
The filter driers are provided with pressure
taps and shutoff valves for isolation when
changing the core. For safety purposes a
service manifold must be attached prior to
filter maintenance.
Figure 32 - Replaceable Core Filter/Drier
DO NOT OVERCHARGE!
Refrigerant overcharging leads to
excess refrigerant in the condenser
coils resulting in elevated compressor
discharge pressure.
CAUTION