TechnicalInstructions LMVSeries
DocumentNo.LV5‐1000
Section7 Page12 SCCInc.
LMV5WillNotModulateProperly
1. EnsurethattheLMV5isinautomaticmodethroughthefollowingmenupath:
ManualOperation>Autom/Manual/Off=Automatic
2. CheckthePIDsettingsandmakesurethattheyaresetfortheapplication.
P‐Part–Thisistheproportionalband.Theproportionalbandincreasesfiringratebasedon
how far below setpoint the temperature / pressure is.Smaller values cause a more
aggressive response to a drop in pressure / temperature relative to setpoint.Values that
aretoosmallwillcausehunting.Typicalsetting:10%to30%.
I‐Part– Thisistheintegralpart, whichservestoeliminatesteadystate "droop"causedby
the proportional band setting.Thus, this works hand in hand with P‐Part to bring the
pressure/temperatureuptosetpoint.Smallervaluescauseamoreaggressiveresponse(a
setting of 1 is most aggressive).Values that are too small will cause overshoot.Typical
setting:80 sec to 300 sec.A setting of 0 deactivates the feature, but this is not
recommended.
D‐Part–Thisisthederivativepart,whichservestoeliminateovershoot,andallowsamore
aggressiveintegralsetting.Largervaluescauseamoreaggressiveresponse.D‐Partisnot
neededonmanysteamboilers.Ifneeded,smallvaluesoflessthan20typicallyworkwell.
Asettingof0deactivatesthefeature.Largevalueswilltypicallycausehunting.
3. Checktheloadlimitparameters(UserMaxLoad,MinLoad,MaxLoad)toverifythattheyare
notlimitingmodulation.
4. Check the load mask parameters under each fuel and ver
ify that they are not preventing
modulation.Thesecanbecheckedusingthefollowingmenupath:
Params&Display>RatioControl>Gas/OilSettings>LoadLimits
Defaultvaluesare:LoadMaskLowLimit=0%,LoadMaskHighLimit=0%.
5. IftheLMV5goestohighfireinphase52,checkparameterStartPointOpundereachfuel.
Thisshouldtypicallybesetto1(lowfire).
Note:If PID values are set properly, the load should change no more than once every 8
seconds on most installations.If PID values are set improperly, the duty cycle of the SQM…
actuatorcanbeexceeded.
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