Tech Controllers ST-976 - Principle of Operation; Lambda Sensor; Working Phases of the Controller; 4.2.1 Fire-Up

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PRINCIPLEOFOPERATION
Theregulatorcontrolsthefanandthefeederwiththeaimofreachingthepre‐settemperaturevalueofwater
tankandCHboiler.Additionally,itcontrolsCHpumpandDHWpump,enablingthemafterthepre‐definedCH
boilertemperaturehasbeenreached.
Dependingonthesettings,thecontrollermayoperateaccordingtostandardalgorithm,automaticalgorithm
orzPIDalgorithm.ItmayalsouseLambdasensor.Themenulayoutmayalsodifferdependingonsettings.
4.1.1 Lambdasensor
Additionally,thecontrolleroperationmaydependonLAMBDAsensorreadings,whichprovidetheinformation
abouttheproportionofoxygeninthefluegas.Onthebasisofthisvalue,theefficiencyoftheburningprocess
isassessed.Iftheamountofoxygenisdifferentthanthepre‐setvalue,theregulatoradjuststhefanspeedas
wellastheamountoffuelfedtotheboiler,inordertomaketheprocessmoreefficient.
WORKINGPHASESOFTHECONTROLLER
ParametersofparticularworkingphasesoftheCHboilerareconfiguredbytheuser.Fire‐upanddampingare
multi‐stageprocessesdescribedbelow.TheremainingphasesdependontheOperationalgorithmselectedby
theuser.
4.2.1 Fire‐up
Thisphaseisinitializedbytheuserinthemainmenu,orbythecontrollersoftwareincertainsituations(e.g.
after periodical cleaning of the furnace during controller operation). There are four stages of the fire‐up
process:
1. Blow‐by
Inthisstagethefanworksatfullspeedinordertocleanthefurnace.
2. Initialfuelfeeding
Inthisstagetheblowforcedecreasestoitsminimumvalue‐1%. The feeder is enabled and operates
throughoutthewholestage.Fuelfeedingtimeissetbytheuserintheservicemenu.
3. Heater
Inthefollowingstageofthefire‐upprocesstheheaterisenabled.Itremainsactiveuntilthesensordetects
flames.Thefeederisinactivewhereasthefanoperatesatthespeeddefinedbythefitterinthefitter’smenu.
4. Stabilization
Delayisthefinalstageofthefire‐upprocess.Itstartswhentheflameshavebeendetected.Duringthisstage
thefirestabilizes.Thefeederoperatesaccordingtooperationtimeandpausetimesettings.Thefanoperates
atthespeeddefinedintheservicemenu.
4.2.2 Standardoperation
Thefeeder andfan operationdepend onthe user’s settingsand currentCHboilertemperature.If current
temperatureismuchlowerthanthepre‐setvalue(e.g.afterthefire‐up),thefeederandthefanoperate
accordingtothesettingsdescribedasMaximumpower.WhentheCHboilerapproachesthepre‐setvalue,the
controllerswitchestoMinimumpowersettings.
4.2.3 Automaticoperation
Once the fire‐up process has been completed, the controller enters automatic mode. In this mode, the
controlleroperationisbasedontheuser‐definedparametersconcerningtheweightandcalorificvalueoffuel
andfanspeedbeforeandafterreachingthepre‐settemperaturevalue.