Application guidelines
34
FRCC.PC.014.A4.22
Operating conditions
Insufficient oil level can be the result of oil depos-
iting itself in pipes and heat exchangers. The oil
deposit can be returned to the crankcase, by in-
creasing velocity for short period, at regular time
intervals or when velocity is too low to ensure
adequate oil returns.
With oil return management these two oil return
mechanisms can be programmed in the CDS302.
Refer to section “Oil level checking and top-up” at
the end of this document for details.
Oil return management
function
60
70
80
90
100
110
120
130
140
150
160
-20
-10
0
10
20
30
40
50
60
70
Evaporating temperature (°F)
Condensing temperature (°F)
Example 1
Example 2
DGT - limit
LP1
HP2
HP1
LP2
Example 1 (R410A, SH = 20°F)
LP switch setting:
LP1 = 48 psig (4.1°F)
HP switch setting:
HP1 = 551 psig (143.6°F)
Risk of operation beyond the application envelope.
DGT protection required.
Example 2 (R410A, SH = 20°F)
LP switch setting:
LP2 = 67 psig (13.1°F)
HP switch setting:
HP2 = 450 psig (125.6°F)
No risk of operation beyond the application envelope.
No DGT protection required.
Discharge gas thermostat
Discharge gas temperature (DGT) protection
is required if the high and low pressure switch
settings do not protect the compressor against
operations beyond its specific application enve-
lope. Please refer to the examples below, which
illustrate where DGT protection is required (Ex. 1)
and where it is not (Ex. 2).
The discharge gas temperature must not exceed
275°F.
A discharge gas temperature protection device
must be installed on all heat pumps. In revers-
ible 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 oper-
ations beyond the compressor’s operating range
will cause serious damage to the compressor!
A DGT accessory is available from Danfoss: refer
to accessories pages at the end of this document.
The discharge gas thermostat accessory kit (code
no.7750009) includes all components required
for installation, as shown below. The thermostat
must be attached to the discharge line within
5.91 inch from the compressor discharge port
and must be thermally insulated and tightly fixed
on the pipe.
Discharge line
Insulation
Bracket
Thermostat
