M&M
R
EFRIGERATION
I
NC
. 3-19
Chapter 3: Economizer Control (Option)
Economizer Control (Option)
The Economizer Control option provides an intermediate pressure port located between the
primary suction and discharge ports on the screw compressor. The Economizer Solenoid out-
put is used to control the flow of liquid into the economizer vessel or to control a suction sole-
noid at the economizer port.
The Economizer Solenoid output may be forced on, forced off, controlled automatically based
on the slide valve position, or sequenced by the master sequencer. The Economizer mode
(AUTO, MAN ON, MAN OFF, or SEQ) and automatic control setpoints can be adjusted from
the Economizer Control screen under the CNTRL hot key.
Automatic Mode
In Automatic mode, the Economizer Solenoid is controlled based on the slide valve posi-
tion of the compressor. When the compressor is running and the slide valve position is
above the cut-in setpoint, the Economizer Solenoid will be energized. When the slide
valve position drops below the cut-out setpoint or the compressor is stopped, the Econo-
mizer Solenoid will be de-energized.
Manual On Mode
When the Economizer Control is in the Manual On mode, the Economizer Output is ener-
gized whenever the compressor is running.
Manual Off Mode
When the Economizer Control is in the Manual Off mode, the Economizer Output is de-
energized at all times.
Sequenced Mode
When the Economizer Control is in the Sequenced mode, the Economizer Output is con-
trolled by the master sequencer controller at the master control panel.
Power Assist (Option)
In low temperature booster applications, more positive suction check valve closure may be
needed. The power assist option supplies this positive closure by allowing high pressure gas
to assist the spring tension of the check valve. The high pressure gas supply is typically taken
from the high stage discharge. When the compressor stops, high pressure gas is vented to
the suction check by opening the power assist solenoid. The solenoid is held open for 30 sec-
onds. The compressor will remain in the stopping state until the power assist solenoid is
closed.
To Next Page
Loading...
Need help?
General