RXB PLUS ROTARY SCREW COMPRESSOR UNITS
OPERATION
070.101-IOM (JAN 13)
Page 33
DUAL-PORT LIQUID INJECTION
The.dual-port.liquid.injection.system.is.designed.to.obtain.
the.most.efficient.compressor.performance.at.high.and.low.
compression.ratios.by.permitting.injection.of.liquid.refriger.ant.
into.one.of.two.ports.on.the.compressor.
The. dual-port. system. contains. all. the. components. of. the.
single-port.system.with.the.addition.of.a.double-acting.sole-
noid.valve.SV9.and.operates.as.outlined.
Solenoid.valve.SV7.is.energized.by.the.microprocessor.when.
the.temperature.element.(TE3),.installed.in.the.oil.piping.after.
the.oil.filter,.exceeds.the.LICO.setpoint..Liquid.refrigerant.is.
then.passed.through.the.tempera.ture.control.valve.TCV1.to.
the. double-acting. solenoid. valve. SV9.. . Depending. on. the.
compres.sor’s.operating.volume.ratio.Vi,.the.micropro.cessor.
will.select.the.flow.of.the.liquid.refrigerant.to.either.compres-
sor.port.3.or.port.4.
When.the.compressor.operates.at.3.5.or.2.2,.Vi.compres.sor.
port.3.(low.Vi).supplies.the.liquid.cooling..At.5.0.Vi,.port.4.
(high.Vi).supplies.the.liquid.cooling.
The. temperature. control. valve. TCV1. is. equalized. to. a.
constant.back.pressure.by.the.differential.pres.sure.control.
valve.PDCV.
Both.the.differential.pressure.control.valve.PDCV.and.the.
double-acting. solenoid. valve. SV9. use. discharge. gas. to.
maintain.downstream.pressure..The.gas.downstream.of.both.
valves.is.bled.off.to.the.compres.sor.suction.to.ensure.steady.
and.constant.operation.of.the.valves.
LIQUID INJECTION
ADJUSTMENT PROCEDURE
1.
.Close.vent.valve.(V4).
2.
.Open.service.valve.(V5).until.ap.proxi.mately.80.PSIG.is.
registered.at.the.Pressure.Indicator.(PI).
3.
.Open.vent.valve.(V4).until.75.PSIG.is.registered.at.the.
Pressure.Indicator.(PI).
4.
.Monitor.the.oil.temperature.of.the.compressor..If.the.oil.
temperature.rises.above.130°F.(R-717),.open.vent.valve.(V4).
a.very.small.amount...This.will.reduce.pressure.on.the.equal-
izer.and.allow.more.refriger.ant.to.flow.to.the.compressor...If.
the.oil.tempera.ture.drops.below.110°F.(R-717),.close.vent.
valve.(V4).a.very.small.amount..This.will.increase.pressure.
on. the. equalizer..The. ideal. condition. is. to. maintain. an. oil.
tempera.ture.as.stable.as.possible...An.incorrect.ly.tuned.liquid.
injection.system.will.cause.extreme.swings.in.the.discharge.
temperature.and.the.oil.temperature.
The vent valve (V4) MUST be open
at least 1/4 turn during normal op-
eration. A higher initial pressure
(step 2) may be required.