KMC Controls CSC-3000 Series - Adjustments and Calibration; Damper Action; Determining the Type of Reset; Adjusting Minimums and Maximums

CSC-3000 Series Pneumatic VAV Reset Volume Controllers 4 Applications Guide, Rev G
Adjustments and Calibration
NOTE: DoNOTadjustresetstartpointandreset
span(upper and lower knobs)without
thoroughlyreviewingtherelevantsections.
Damper Action
Thedamperactionisfactory-setatNormallyOpen
(N.O.).TochangetoNormallyClosed(N.C.),per-
formthefollowingsteps:
1. Loosenthedamperselectionscrew.
2. Turntheselectiondialclockwiseuntilthe“NC”
arrowalignswiththe“DAMPER”arrow.
NOTE: Accuracy in the alignment of the arrows is
very important. Make this adjustment as
exact as possible.
3. Tightentheselectionscrew.Be sure the
screw is tight(2to4in-lbs.oftorque),but if
overtightened, the plastic will strip out.
DIRECT Reset Minimum and Maximum
Determining the Type of Reset
ThefollowingtableshowswhenDirectResetor
ReverseResetisrequired.Determinetheresettype
basedonthetemperatureoftheprimaryairentering
theVAVboxandwhetherthethermostatinthespace
isdirectorreverseacting.
Adjusting Minimums and Maximums
Whenadjustingtheminimumandmaximumairow
seings,theoutputrespondsslowlytochangesin
thesetpoint.Waitfortheowratetostabilizeaer
makinganadjustment(usually20to30seconds)be-
foremakingfurtheradjustments.Also,ifthedamper
positionisallthewayclosedoropenwhenstarting
thisstep,turntheadjustmentonefullturn,andthen
wait20to30secondsforachangeintheowread-
ingoftheMagnehelicgauge.Ifnochangeoccurs
aerthistime,repeatuntiltheowratechanges.
NOTE: Thedirectresetillustrationaboveassumes
norelaysareconnectedbetweenthe
thermostatand“T”port.
ForDirectReset(DAthermostatforcoolingorRA
thermostatforheating),performthefollowingsteps:
1a.OntheCSC-3000,disconnectthe“T”portand
leaveitopen.Temporarilyplugthetubing(but
doNOTplugtheport).
1b.Alternately,insteadofremovingthetubingfromthe
Tport,(temporarily)removetheplugfromtheCSC-
3000’s“G”port.
2. AdjusttheLOSTAT∆P(centerdial)one
adjustmentatatimeuntilthedesiredMinimum
airowisreadattheMagnehelicgaugeandis
stable.
NOTE: Adjustthedialnomorethanabouta
halfrotationatatime.Aermakingany
adjustment,waitapproximatelytenseconds
whilewatchingformotioninthedamper
sha.Ifnomotionoccurs,makethenext
adjustment.
NOTE: IF the LO STAT ∆P Limit must be set at
“0” (zero minimum),
donotturntheLO
STAT∆Pknobfullyclockwise.Theknob
willadjustoneandone-halfturnsaera
zerominimumisreached.TurningtheLO
STAT∆Pknobfullyclockwisewillresult
inanegativeresetcondition.Thismeans
thatwhenthecontrollerbeginstoresetat
theresetstartpoint,itmustrstovercome
thenegativeadjustmentandwillnotbegin
toresetfrom“0”untilahigherthermostat
resetpressureisreached.Thisnegative
resetwillalsoreducetheeectiverange
ofthecontrollerbyreducingthelowend
reset,narrowingtheresetspan.Ifazero
minimumisrequired,adjusttheLOSTAT
∆Pknobuntilthecontrollerjustbeginsto
crackthedamperopen,andthenback-o
one-quarterturnandverifyzeroairow.
(Thisistypically2-1/2knobrotations
counterclockwisefromthefullyclockwise
position.)
Primary Air Thermostat Reset Type
Cooling
DA
DirectReset
RA ReverseReset
Heating
DA
ReverseReset
RA DirectReset
Thermostat Pressure
Max. Airflow
Min. Airflow
Reset Start Point
• 3 psig: CSC-3021/3026
• 8 psig: CSC-3011/3016/3017/3025
• 10 psig: CSC-3023
Reset Span (5 psig)
(Cooling w/ DA Thermstat or
Heating w/ RA Thermostat)