Siemens LMV52.440B1 - Page 169

LMVSeriesTechnicalInstructions 
DocumentNo.LV5‐1000
SCCInc. Page17 Section5
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 TheLMV52/VFD/blowerresponsecanbewatchedtocheckforproperoperation.Thiscanbe
doneinstandbyPhase12(burneroff)byusingthefollowingmenupath:

Params&Display>RatioControl>Gas/OilSettings>CurveParamsorCurveSettings
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Whentheblowerisataspeedotherthanwhatisdisplayed,anarrow(>)isdisplayedontheAZL
nexttotheVFDposition.When
theblowerisatthedisplayedspeed,acolon(:)isdisplayedonthe
AZLnexttotheVFDposition.ByrampingtheVFDupanddown,theresponseoftheVFDcanbe
observed.Transitioningbackandforthbetweenacolon(:)anda(>)afterrampingtheVFDupor
downindicatesaspeedcontrolissue.
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 TheLMV52'sclosedloops
peedcontrolisbasedonPI(proportional‐inte gral)logic. Theresponseof
thisloopcanbetunedusingthefollowingmenupath:
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Params&Display>VSDModule>Configuration> Speed>SettelingTime
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In
mostcases,thisdoesnotneedtobetuned.SeeSection3(Parameters)forafullexplanation.
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 Theabsolutespeedasreadinrealtimebythespeedwheelcanbewatchedatanypointintime.
WhentheLMV52isnotm
odulatingorwhenitisatafixedVFDspeed(pre‐purge,post‐pur
ge,
ignition,etc.),thespeedshouldbesteady,notdeviatingbymorethan+/‐10RPM.Thiscanbe
viewedat:

Params&Display>VSDModule>Co
nfiguration>Speed>AbsoluteSpeed
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 Thecombustionairpressureswitchshouldbesetbytakingth
eVFDto10%belowthelowest
anticipatedlowfirespeed(iflowfireis50%,taketheVFDto40%)andsettingtheswitchtoopenat
thatpoint.Thisshouldmax
imizethesafetypotentialofthecombustionair
pressureswitchand
minimizenuisancetrips.ThiscanbedoneinstandbybysettingthehomepositionoftheVFDto
40%andsettingtheswitch.
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 Inmostapplicationswithanairdamper,thereislittlereasontodecreaseblowerspeedbelowabout
50%VFD(30Hz).PowerconsumptiondecreasesbythecubeoftheRPMevenwithoutthe
additionalrestrictionofanairdamper
.Referencinginformationfromthe"CentrifugalBlower
Fundamentals"sectiononthepreviouspages,decreasingthespeedofa25HP(18.62kW)motor
from3600RPM(60Hz)to1800RPM(30Hz)willcausethepowerconsumptiontobereducedfrom
18.62
kWdownto2.32kW,anelectricalsavingsofover800%.
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 AVFDalonewithoutanairdamperorslidingheadofferslimitedaccuracyandrepeatabilityforthe
airflowathigherbu
rnerturndowns.Formostboilerburners,modulatingtheVFDalonewithoutan
airdamperisokayfor
turndownsof4‐to‐1orless.UsingonlyaVFDforairflowregulationathigher
turndownsmayleadtoairflowrepeatabilityissues.
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