Installation, Operation and Maintenance Manual
Page
82
of
100
12
Superheat and Suction Pressure Troubleshooting Guide
Low Suction Pressure and High Superheat
1.
Moisture, wax, dirt in system
2.
High superheat adjustment
3.
Gas charge condensation
4.
Dead thermostatic element charge
5.
Wrong thermostatic charge
6.
Evaporator pressure drop
–
no external equalizer
7.
External equalizer location
8.
Restricted or capped external equalizer
9.
Low refrigerant charge
10.
Liquid line vapor
a.
Vertical lift
b.
High friction loss
c.
Long or small line
d.
Plugged drier or strainer
11.
Low pressure across valve
a.
Vertical lift
b.
Undersized distributor nozzle or circuits
c.
Low condensing temperature
High Suction Pressure and Low Superheat
1.
TXV seat leaking
2.
Low superheat adjustment
3.
Improper bulb installation
a.
Poor thermal contact
b.
Warm location
4.
Wrong thermostatic charge
5.
Bad compressor
–
low capacity
6.
Moisture, wax, dirt in system
7.
Incorrectly located external equalizer
Low Suction Pressure and Low Superheat
1.
Low load
a.
Insufficient air flow
b.
Dirty air filters
c.
Coil icing
2.
Poor air distribution
3.
Poor refrigerant distribution
4.
Improper compressor/evaporator balance
5.
Evaporator oil logged