Operating conditions
70
65
60
55
50
45
40
35
30
25
20
15
10
-30
-25
-20
-15
-10
-5
0
5
10
15
20
Cond. temp
. (°C
)
Evap. temp. (°C)
LP1
HP2
HP1
R410A
DGT - limit
Example 1
Example 2
LP2
Discharge line
Insulation
Bracket
Thermostat
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!
A high-pressure (HP) safety switch is required to
shut down the compressor should the discharge
pressure exceed the values shown in the table
section “System pressure test”. The high-pressure
switch can be set to lower values depending on
the application and ambient conditions. The HP
switch must either be placed in a lockout circuit
or consist of a manual reset device to prevent
cycling around the high-pressure limit. If a
discharge valve is used, the HP switch must be
connected to the service valve gauge port, which
must not be isolated.
High and low
pressure protection
High pressure
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, SH = 11 K)
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, SH = 11 K)
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.
19
FRCC.PC.028.A5.02
Application Guidelines
