RXB PLUS ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
070.101-IOM (JAN 13)
Page 41
TROUBLESHOOTING GUIDE
Successful.problem.solving.requires.an.organ.ized.ap.proach.
to. define. the. problem,. identify. the. cause,. and. make. the.
proper.correction.
ABNORMAL OPERATION
ANALYSIS and CORRECTION
Four. logical. steps. are. required. to. analyze. an. opera.tional.
problem.effectively.and.make.the.necessary.correc.tions:.
.
1.
.Define.the.problem.and.its.limits.
2.
.Identify.all.possible.causes.
3.
.Test.each.cause.until.the.source.of.the.problem.is.found.
4.
.Make.the.necessary.corrections.
The. first. step. in. effective. problem. solving. is. to. define. the.
limits.of.the.problem..If,.for.example,.the.compres.sor.periodi-
cally.experienc.es.high.oil.tempera.tures,.do.not.rely.on.this.
observation.alone.to.help.identify.the.problem...On.the.basis.
of.this.information,.the.apparent.corrective.measure.would.
appear.to.be.a.re.adjustment.of.the.liquid.injection.system..
Lowering.the.equalizing.pressure.on.the.thermal.expansion.
valve.would.in.crease.the.refriger.ant.feed.and.the.oil.tem-
perature.should.drop..
If. the. high. oil. temperature. was. the. result. of. high. suction.
superheat,.however,.and.not.just.a.matter.of.improper.liquid.
injection.adjust.ment,.increasing.the.liquid.feed.could.lead.to.
other.problems..Under.low.load.conditions.the.liquid.injection.
system.may.have.a.tendency.to.overfeed...The.high.suction.
superheat.condition,.moreov.er,.may.only.be.tempor.ary..When.
system.conditions.return.to.normal,.the.unit’s.liquid.injection.
will. overfeed. and. oil. temperature. will. drop.. In. solving. the.
wrong.problem,.a.new.problem.was.created.
The.following.list.of.abnormal.system.condi.tions.can.cause.
abnormal.operation.of.the.
RXB
.compressor.unit:
1.
.Insufficient.or.excessive.refrigeration.load.
2.
.Excessively.high.suction.pressure.
3.
.Excessively.high.suction.superheat.
4.
Excessively.high.discharge.pressure.
5.
.Inadequate.refrigerant.charge.or.low.receiv.er.level.
6.
. Excessively. high. or. low-temperature. coolant. to. the. oil.
cooler.
7.
.Liquid.return.from.the.system.(carryover).
8.
.Refrigerant.underfeed.or.overfeed.to.the.evapor.ators.
9.
. Blocked. tubes. in. the. water-cooled. oil. cooler. from. high.
mineral.content.of.the.water.
10.
.Insufficient.evaporator.or.condenser.siz.ing.
11.
.Incorrect.refrigerant.line.sizing.
12.
.Improper.system.piping.
13.
.Problems.in.electrical.service.to.the.compres.sor.unit.
14.
.Air.and.moisture.present.in.the.system.
Make.a.list.of.all.deviations.from.normal.plant.operation.and.
normal.compressor.unit.operation...Delete.any.items.which.
do.not.relate.to.the.symptom.and.separately.list.those.items.
that.might.relate.to.the.symptom..Use.the.list.as.a.guide.to.
further.investigate.the.problem.
The.second.step.in.problem.solving.is.to.decide.which.items.
on.the.list.are.possible.causes.and.which.items.are.additional.
symptoms..High.discharge.temperature.and.high.oil.tempera-
ture.readings.may.both.be.symptoms.of.a.problem.and.not.
casually.related..High.suction.superheat.or.a.low.receiver.
level,.however,.could.cause.both.symp.toms.
The.third.step.is.to.identify.the.most.likely.cause.and.take.ac-
tion.to.correct.the.problem..If.the.symptoms.are.not.relieved,.
move.to.the.next.item.on.the.list.and.repeat.the.procedure.
until.you.have.identified.the.cause.of.the.problem...Once.the.
cause.has.been.identified.and.con.firmed,.make.the.neces-
sary.correc.tions.