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RXB PLUS ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
070.101-IOM (JAN 13)
Page 64
COMMUNICATIONS
The. use. of. communications. such. as. serial. and. ethernet.
in. industrial. environments. are. commonplace..The. proper.
installation.of.these.networks.is.as.important.to.the.proper.
operation. of. the. communications. as. all. of. the. preceding.
practices.are.to.the.equipment..
Serial.communications.cable.needs.to.be.of.the.proper.gauge.
based.on.the.total.cable.distance.of.the.run..Daisy-chaining.
is.the.only.acceptable.style.of.running.the.communications.
cable..While.Star.Networks.may.use.less.cable,.they.more.
often.than.not.cause.problems.and.interruptions.in.communi-
cations,.due.to.varying.impedances.over.the.varying.lengths.
of.cable..Ground.or.drain.wires.of.the.communications.cable.
are.to.be.tied.together.at.each.daisy-chain.connection.and.
only.taken.to.ground.in.the.central.control.system.panel.
It.is.important.to.carefully.consider.the.type.of.cable.to.be.
used..Just.because.a.cable.has.the.proper.number.of.con-
ductors.and.is.shielded.does.not.mean.it.is.an.acceptable.
cable..Frick.recommends.the.use.of.Belden.#9829.for.RS-422.
communications.and.Belden.#.9841.for.RS-485.up.to.2000.
feet.(600.Meters).total.cable.length..Refer.to.Frick.drawing.
649D4743.for.more.detail
Comm Port Protection:
.Surge.suppression.for.the.comm.
ports.may.not.be.the.best.method,.since.suppression.is.re-
quired.to.divert.excess.voltage/current.to.ground..Therefore,.
the.success.of.these.devices.is.dependent.on.a.good.ground.
(covered.earlier.in.this.section)..This.excess.energy.can.be.
quite.high.and.without.a.proper.ground,.it.will.access.the.
port.and.damage.it.
Isolation.or.Optical.Isolation.is.the.preferred.comm.port.pro-
tection.method..With.optical.isolation,.there.is.no.continuity.
between.the.communications.cable.and.the.comm.port..There.
is.no.dependence.on.the.quality.of.the.ground..Be.sure.to.
know.what.the.voltage.isolation.value.of.the.optical.isolator.is.
before.selecting.it..These.may.range.from.500.to.4000.Volts..
Frick. Optical. Isolation. Kits. are. offered. under. part. number.
639C0133G01..One.kit.is.required.per.comm.port.
UPS POWER AND QUANTUM
™
LX PANELS
Johnson. Controls,. Inc.. does. not. advise. nor. support. the.
use.of.uninterrupted.power.supply.systems.for.use.with.the.
Quantum
™
LX.panel..With.a.UPS.system.providing.shutdown.
protection.for.a.Quantum.panel,.the.panel.may.not.see.the.
loss.of.the.3-phase.voltage.on.the.motor.because.the.UPS.
may.prevent.the.motor.starter.contactor.from.dropping.out..
With.the.starter.contactor.still.energized,.the.compressor.aux-
iliary.will.continue.to.feed.an.“okay”.signal.to.the.Quantum
™
LX.
panel..This.may.allow.the.motor.to.be.subjected.to.the.fault.
condition.on.the.3-phase.bus.
A. couple. of. fault. scenarios. are:. 1..The. 3-phase. bus. has.
power.“on”. and.“off”. in. a. continuous. cycle. manner. which.
may.cause.the.motor.to.overheat.due.to.repeated.exces-
sive.in-rush.current.experiences..2..The.motor.cycling.may.
damage. the. coupling. or. cause. other. mechanical. damage.
due.to.the.repeated.high.torque.from.rapid.sequential.mo-
tor.“bumps.”.3..Prolonged.low.voltage.may.cause.the.motor.
to.stall.and.possibly.overheat.before.the.motor.contactor.is.
manually.turned.off.
Under.normal.conditions,.the.loss.of.3-phase.power.will.shut.
down.the.Quantum
™
LX.panel.and.it.will.reboot.upon.proper.
power.return..If.the.panel.was.in.“Auto,”.it.will.come.back.and.
return.to.running.as.programmed..If.the.unit.was.in.“Remote,”.
the.external.controller.will.re-initialize.the.panel.and.proceed.
to.run.as.required..If.the.panel.was.in.“Manual”.mode,.the.
compressor. will. have. to. be. restarted. manually. after. the.
3-phase.bus.fault/interruption.has.been.cleared./.restored.
If.the.local.power.distribution.system.is.unstable.or.prone.
to. problems. there. are. other. recommendations. to. satisfy.
these.problems..If.power.spikes.or.low.or.high.line.voltages.
are.the.problem,.then.a.constant.voltage.(CV).transformer.
with.a.noise.suppression.feature.is.recommended..Johnson.
Controls,. Inc.. can. provide. these. types. of. transformers. for.
this.purpose..Contact.Johnson.Controls.for.proper.sizing.(VA.
Rating).based.on.the.requirement.of.the.job..If.a.phase.loss.
occurs,.then.you.will.typically.get.a.high.motor.amp.shutdown..
If.the.problem.continues,.an.analysis.of.the.facility’s.power.
supply.quality.may.be.necessary.
NOTE: It is very important to read the installation instructions thoroughly
before beginning the project. Make sure you have drawings and instructions
for the equipment being installed. If not, call the manufacturer to receive the
proper instructions and drawings. Every manufacturer of electronic equip-
ment should have a knowledgeable staff, willing to answer your questions
or provide additional information. Following correct wiring procedures will
ensure proper installation and consequently, proper operation of your elec-
tronic equipment.