Danfoss VZH052 Manual page 35

Manage operating envelope
Discharge temperature
protection
For VZH052-065 compressors, the external
Discharge Gas Temperature protection (DGT)
is required in zone 1.4 or if the high and low
pressure switch settings do not protect the
compressor against operation beyond its
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Example 1 (R410A, SH = 6K / 10.8°F)
LP switch setting:
LP1 = 3.3 bar (g) / 48 psig (-15.5°C / 4.1°F)
HP switch setting:
HP1 = 38 bar (g) / 551 psig (62°C / 143.6°F)
Risk of operation beyond the application envelope.
DGT protection required.
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 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 thermostat accessory kit (code
7750009) includes all components required
for installation as shown on the right. DGT
installation must respect below requirements:
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). Please notice the envelope boundaries
change based on different speed limits.
DGT limit
-25 -20 -15 -10 -5 0
Evaporating temperature (°C)
Example 2 (R410A, SH = 6 K / 10.8°F)
LP switch setting:
LP2 = 4.6 bar (g) / 67 psig (-10.5°C / 13.1°F)
HP switch setting:
HP2 = 31 bar (g) / 450 psig (52°C / 125.6°F)
No risk of operation beyond the application envelope.
• The thermostat must be attached to the
discharge line within 150 mm (5.91 inch) from
the compressor discharge port and must be
thermally insulated and tightly fixed on the
pipe.
• The DGT should be set to open at a discharge
gas temperature of 135°C (275°F) or lower.
Discharge line
LP1
Example 1
LP2
Example 2
5 10 15 20 25 30
Thermostat
Insulation
Bracket
AB237586440343en-000601
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