TechnicalInstructions LMVSeries
DocumentNo.LV5‐1000
Section4 Page24 SCCInc.
Properly adjustedPIDvalues will result inthepressure / temperature staying within+/‐3% of
setpointwithoutconstantlychangingtheloadandmodulatingtheactuators.
P‐Part (Proportional Band)‐Increases firing rate based on how far below setpoint the
temperature / pressure is.Smaller values cause a more aggressive P response to a drop in
pressure / temperature relative to setpoint.Values that are too small will cause hunting.
Typicalsetting:10% to30%.
I‐Part (Integral)‐Serves to eliminate steady state "droop" caused by the proportional band
setting.Thus, this works hand in hand with P‐Part to bring the pressure / temperature up to
setpoint.Smallervaluescause amore aggressiveIresponse(asetting of1ismostaggressive).
Valuesthataretoosmallwillcauseovershoot.Typicalsetting:80secto300sec.Asettingof0
deactivatesthefeature,butthisisnotrecommended.
D‐Part (Derivative)‐Serv
es to eliminate overshoot, and allows a more aggressive integral
setting.Larger values cause a more aggressive D response.D‐Part is not needed on many
steam boilers.If neede d, small values of less than 20 typically work well.A setting of 0
deactivatesthefeature.Largevalueswilltypicallycausehunting.
8. AfterthePIDloophasbeenadjusted,itispossiblethattheloadwillstillmoveupand downbya
small amount (1‐2% load).If this is the case, adjusting parameter MinActuatorStep may help
eliminatethis"micro‐hunting".Thisparametercanbefoundinthefollowingmenu:
Params&Display>LoadController>ControllerParam
MinActuatorStepisbasicallyadeadbandfortheoutputofthePIDloop.Typicalsetting:
1%to
4%.Valuesabove5%couldcausehuntingissuesinsomeapplications.
SuggestedColdStart(ThermalShockProtection)Setup
The LMV51.1 and LMV52 have an internal load control and therefore have the ability to perform
thermalshockprotection.ThermalshockprotectiononlyfunctionswhentheLMV5isinaninternalload
controllermode,namelyIntLC,IntLCX62,orIntLCBus(seechartonpreviouspages).
Thecold startfeaturerequiresthatthetemperatureorpressureofthe boileris measuredby asensor
connectedtotheLMV5.
Forahot waterboiler(temperatur
e‐basedmodulation),the sametemperaturesensor thatisusedfor
modulationmustbeusedforthecoldstartfeature.Forasteamboiler(pressure‐basedmodulation),a
temperature sensor is also highly recommended for cold start.Temperat
ure senso rs are highly
recommended since pressure does not always represent temperature in a non‐firing steam boiler,
especiallywhenmultiplesteamboilersarepipedtothesamesteamheader.Theparagraphsbelow will
onlymentiontemperature‐basedcol dstart,butthesameideasalsoapplytopressure‐basedcoldstart.
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