Tech Controllers ST-976 - Protections; Thermal Protection of the Ch Boiler; Automatic Sensor Control; Thermal Protection of the Ch Boiler (Stb)

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PROTECTIONS
Inordertoensuresafeandfailure‐freeoperation,theregulatorhasbeenequippedwitha
rangeofsafeguards.Incaseofalarm,asoundsignalisactivatedandthedisplayshowsanappropriate
message.
THERMALPROTECTIONOFTHECHBOILER
Thecontrollerisequippedwithabimetallicmini‐sensor(placednexttoCHboilertemperaturesensor),which
automaticallydisconnectsthefanfromthepowersupplywhenthealarmtemperatureof90°Cisexceeded.It
preventsthewaterintheinstallationfromboilingincaseofCHboileroverheatingorcontrollerdamage.After
thisprotectionhasbeenactivatedandthetemperaturehasdroppedtoasafelevel,thesensorautomatically
unlocksitself.Ifthissensorisdamagedoroverheated,thefanisalsodisconnected.
 InthecaseofCHboilerprotectioninaclosedsystem,aSTBtypetemperaturelimiterisusedinstead
ofabimetallicmini‐sensor.
AUTOMATICSENSORCONTROL
Ifoneofthetemperaturesensors(CH,DHW)isdamaged,analarmsoundisactivatedandthedisplaymessage
informsaboutthefailure;e.g.:CHsensordamaged.Thefanisdisabled.Thepumpisenabledregardlessofthe
currenttemperature.
IftheCHsensorisdamaged,thealarmisactiveuntilanewsensorisinstalledandtheCHboilerisdisabled.
InthecaseofDHWsensordamage,thealarmshouldbeswitchedoffbypressing –thecontroller
willdeactivatethealarmandrestoreoperation(themodesinvolvingDHWtankwillnotbeavailable).Anew
sensorshouldbeinstalledsothatallmodesofCHboileroperationcouldbeavailable.
THERMALPROTECTIONOFTHECHBOILER(STB)
InaclosedCHsystem,thecontrollerisequippedwithSTBsafetythermostatwhichprotectstheCH boiler
against an excessive temperature increase. When the temperature exceeds the pre‐set ‘switch off’value
(defaultsetting:95
o
C),thecontactsinthefanpowersupplycircuitareopened.Thefanmaybeactivatedagain
onlymanuallybypressing‘reset’onthesafetythermostatcasingafterthesensorcoolsdown.
FUSE
TheregulatorhasaWT6.3Atubefuse‐linkprotectingthenetwork.
WARNING
Higheramperagefuseshouldnotbeusedasitmaydamagethecontroller.
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