Operating conditions
A 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 (Ex.1) and where it is not
(Ex.2). A discharge gas temperature protection
device must be installed on all heat pumps. In
reversible air-to-air and air-to-water heat pumps
the discharge temperature must be monitored
during development test by the equipment
manufacturer. The DGT should be set to open
at a discharge gas temperature of 135°C. 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!
The discharge gas temperature must not exceed
135°C.
The discharge gas thermostat accessory kit (code
7750009) includes all components required for
installation as shown below. The thermostat must
be attached to the discharge line within 150 mm
from the compressor discharge port and must be
thermally insulated and tightly fixed on the pipe.
Discharge temperature
protection
Example 1 (R410A)
LP switch setting:
LP1 = 3.3 bar (g) (-15.5°C)
HP switch setting:
HP1 = 38 bar (g) (62°C)
Risk of operation beyond the applica-
tion envelope.
DGT protection required.
Example 2 (R410A)
LP switch setting:
LP2 = 4.6 bar (g) (-10.5°C)
HP switch setting:
HP2 = 31 bar (g) (52°C)
No risk of operation beyond the
application envelope.
No DGT protection required.
70
65
60
55
50
45
40
35
30
25
20
15
10
-30
-25
-20
-15
-10
-5
0
5
10
15
20
C
ond. temp
. (°C
)
Evap. temp. (°C)
LP1
HP2
HP1
Map example R410A
DGT - limit
Example 1
Example 2
LP2
Discharge line
Insulation
Bracket
Thermostat
10
-10
5
0
15
-5
20
25
30
35
40
45
50
55
60
65
70
75
80
85
-35
-40
-45
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
Evaporating temperature (°C)
Condensing temperature
(°
C
)
SH 30K
SH 5K
SH 10K
68.3
41.7
62
Map CH485
20
FRCC.PC.026.A4.02
Application Guidelines
