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4.0 Low/Medium Temperature System Oil Management (R-404A,
R-407A, R-407C, R-407F, R-507A, R-448A, R-449A)
Oil supply system components are shown in Fig. 16.
4.1 Oil Pressure Requirements
System pressure is used to generate the oil pressure
required to lubricate bearings and provide the oil that
acts as a seal between the screw rotors and the bores.
Oil pressure is monitored continuously during compres-
sor operation. The oil pressure must meet the following
criteria, based on P
DISCHARGE
shown in Fig. 18, Oil System Schematic:
1. P
> [0.7 x (P
OIL
DISCHARGE
+ 0.5 bar] 15 seconds after start
2. P
> [P
OIL
SUCTION
(Air-Cooled C models; A in 5th digit of model
numbers)
[P
+ 1.0 bar] 45 seconds after start
SUCTION
(Refrigeration models; R in 5th digit of model
numbers)
[P
+ 1.0 bar] 75 seconds after start
SUCTION
(Water-Cooled models: W in 5th digit of model
numbers)
The unit control system must monitor the oil pressure dif-
ferential, as well as the operating condition, so the com-
pressor can be shut down if the minimum requirements
are not met for any duration exceeding 15 seconds.
This time delay has two functions: first, to avoid nuisance
tripping during normal and transient operation, and sec-
ond, to allow the system sufficient time to develop pres-
sure differential during start-up.
The compressor must be shut down and prevented from
restarting when the low oil pressure safety is tripped.
The safety should be a manual reset type that locks out
compressor operation until the system is serviced.
Carlyle offers a Compressor Protection Module package
to provide protection against loss of oil flow, reverse-
rotation, and elevated discharge gas temperature. Appli-
cation of this package provides equal alternate protection
to the method described above. The Carlyle R-404A
Compressor Protection Module package part number is
6BSB000603.
, P
and P
, as
SUCTION
OIL
– P
) + P
]
SUCTION
SUCTION
9
8
7
6
5
4
3
2
1
0
0
50
100
Discharge - Suction Pressure (psi)
Fig. 16 — Oil Supply at Compressor
4.2 Oil Separator Recommendations
The low/medium temperature Paragon compressor will
require an oil separator. The combined oil capacity of the
oil separator sump, the oil reservoir, and the oil cooler will
vary greatly depending on system design and the num-
ber of compressors applied. Carlyle recommends that
the oil reservoir of the system is large enough to hold 4
gallons of oil for each compressor applied.
Contact Carlyle Application Engineering for additional oil
separator information.
4.3 Oil Heater Recommendations
For the typical oil separators used with the Paragon com-
pressor, a 500-watt flexible-band heater is recom-
mended. The heater should be wired to operate when the
compressor is OFF. This minimizes the migration of
refrigerant to the oil stored in the oil separator reservoir.
Carlyle recommends monitoring the temperature of the
oil in the oil separator reservoir. If oil temperatures climb
above 190°F (88°C), the heater element should be de-
energized to prevent oil overheating.
Figure 13 shows the minimum oil temperatures that must
be maintained when the compressor is not operating
based on the outdoor ambient temperature (OAT).
4.4 Oil Level Safety Switch
An oil level safety switch must be installed in the sump of
the oil separator or the oil reservoir, depending on the
system design. Carlyle recommends a float style switch
which opens if the oil level falls below a safe point.
Enough oil should remain in the sump when the switch is
opened for the compressor to operate for at least one
minute before completely running out of oil.
Compressor Only Oil Flow
150
200
250
300
350
23
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