Operating manual- SAB 355 (including ATEX)
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side, these pressures will act across a piston inside the cold-start valve to partially overcome the
spring force. When the differential pressure reaches and exceeds 2.0 bar [30 psi], the piston fully
overcomes the spring force and powers the valve fully open for a very low operating pressure
drop.
Booster applications
For booster applications, the valve is equipped with a light spring, which produces 0.5 bar [7 psi]
oil pressure above suction pressure before it fully powers open. An oil pump is required to ensure
compressor lubrication.
The unit is also equipped with a suction check valve by-pass. The oil separator will slowly bleed
down to approximate system suction pressure when the unit is stopped. This allows the compres-
sor drive motor to have an easier start, and the discharge check valve will seat more tightly. See
section
6.17 Suction check valve by-pass
for operation.
Note:
For alarm descriptions and shutdown or cut-out parameters, see separate control system
manual.
Fig. 19: Cold-start valve
Open
Closed
P3 - To suction
P2 - To
condenser
P1 - From
oil separator
P1
P2
P3