Johnson Controls SABROE Unisab III Control, Engineering Manual

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Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
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Alarms and shutdowns
The high oil balance pressure reduction supervision function is operative when the compressor is
running.
2.2.42 Low balance pressure reduction alarm
This alarm is released if the calculated balance pressure reduction P
bal_press_red, rel
= P
disch, abs
– P
oil_press_
2, abs
is lower than the low alarm limit. See Table 9.
The low oil balance pressure reduction supervision function is operative when the compressor is running
and the
Balance pressure reduction function is active, i.e. the AUX output is OFF, and with a delay of 5
sec.
2.2.43 Low balance pressure reduction shutdown
This shutdown is released if the calculated balance pressure reduction P
bal_press_red, rel
= P
disch, abs
– P
oil_
press_2, abs
is lower than the low shutdown limit. See Table 9.
The low oil balance pressure reduction supervision function is operative when the compressor is running
and the
Balance pressure reduction function is active, i.e. the AUX output is OFF, and with a delay of 5
sec.
2.2.44 Low discharge temperature difference alarm
This alarm is released if the calculated discharge temperature difference T
disch_diff
= T
disch
– T
oil
is lower
than the low alarm limit. See Table 9.
The low discharge temperature difference supervision is operative when the compressor is running at
“Full capacity”, which is defined as Yield >/= 98 %.
With a hysteresis of 5.0 %, this means that the alarm supervision must be activated when Yield >/= 98%
and deactivated when Yield < 93%.
The low discharge temperature difference alarm is delayed at compressor start by the timer Discharge
diff. start . After the Discharge diff. start timer has run out, the alarm is further delayed during operation
by the timer Discharge diff. delay , see Table 52.
2.2.45 High suction pressure gradient alarm
This alarm is released if the calculated suction pressure gradient P
suct_grad
= dP
suct, abs
/dt is higher than
the high alarm limit. See Table 9 and Table 15.
The suction pressure gradient supervision function is operative when the compressor is running.
2.2.46 High suction pressure gradient shutdown
This shutdown is released if the calculated suction pressure gradient P
suct_grad
= dP
suct, abs
/dt is higher
than the high alarm limit. See Table 9 and Table 15.
The suction pressure gradient supervision function is operative when the compressor is running.
2.2.47 High separator flow (screw compressor)
This function limits the compressor capacity to a calculated limit at certain running conditions. When the
difference pressure across the compressor is too low, the capacity is limited in order to protect the unit
against oil carry-over to the system.
2.2.48 High liquid level (reciprocating compressors)
This alarm is released if the capacity limiting function is active. The high liquid limiter will reduce com-
pressor capacity as long as the liquid level is high in the evaporator. When the liquid level is back to nor-
mal, and after the
Liquid level delay has timed out, the alarm is reset.