Operating conditions
Discharge gas temperature
protection (DGT)
DGT protection is required if the high and low
pressure switch settings do not protect the
compressor against operations beyond its
specific application envelope. Please refer to
the examples below, which illustrate where DGT
protection is required (n°1) and where it is not
(n°2).
The compressor must not be allowed to cycle
on the discharge gas thermostat. Continuous
operations beyond the compressor’s operating
range will cause serious damage to the
compressor!
A DGT accessory is available from Danfoss: refer
to section “Spare parts & accessories”.
The discharge temperature depends mainly on
the combination of evaporating temperature,
condensing temperature and suction gas
superheat. Discharge gas temperature should
be controlled with an isolated thermocouple or
thermostat attached to the discharge line 15 cm
(6 inches) from the compressor shell. Maximum
discharge gas temperature must not exceed
135°C (275°F) when the compressor is running
within the approved operating envelope.
Maximum discharge gas
temperature
R22 - SH 11K
MLZ / MLM
10
15
20
25
30
35
40
45
50
55
60
65
70
75
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
Evaporating temperature (°C)
C
on
de
ns
in
g
te
m
pe
ra
tu
re
(°
C
)
Example 1
Example 2
LP1
LP2
HP1
HP2
Example 1 (R22, SH = 11 K)
LP switch setting: LP1 = 2 bar (g) (-15°C)
HP switch setting: HP1 = 23.8 bar (g) (61°C)
The LP and HP switches don't protect sufficiently from opera-
tion outside the envelope. A DGT protection is required to avoid
operation in the hatched area.
Example 2 (R22, SH = 11 K)
LP switch setting: LP2 = 2.5 bar (g) (-10°C)
HP switch setting: HP2 = 18 bar (g) (49°C)
The LP and HP switches protect from operation outside the
envelope. No DGT protection required.
Discharge line
Insulation
Bracket
Thermostat
32
FRCC.PC.015.A8.02
Application Guidelines
