KMC Controls CSC-3000 Series - Reset Start Point; Reset Span

CSC-3000 Series Pneumatic VAV Reset Volume Controllers 6 Applications Guide, Rev G
Reset Span
NOTE: In almost all applications, the reset span
never needs adjusting. Do not change the
default 5 psi unless really necessary.
Theresetspanisthethermostat’seectivereset
rangeforthecontroller.Aresetspanof5psimeans
thatitwilltakea5psipressurechangemeasured
fromtheresetstartpointtoresettheowrateofthe
VAVbox.
3 psig
8 psig
13 psig
Thermostat Pressure
Max. Airflow
Min. Airflow
Reset Start Point (8 psig)
Reset Span (5 psig)
NOTE: Resetspanisthepressurechangeat“T”
abovetheresetstartpointthatcausesthe
owsetpointtomovefromoneextremeto
theother.Inadirectresetapplication,the
owsetpointwillchangefromminimum
tomaximumowabovethestartpoint.In
areverseresetapplication,theresetwill
changefrommaximumtominimumow
abovethestartpoint.
TheCSC-3000seriesarefactorysetwitharesetspan
of5psi.Thisisstandardinmostapplicationsand
doesnottypicallyrequireadjustment.Leavingthis
adjustmentatthefactoryseingisrecommended.
Ifnecessary,theresetspancanbeadjusted(between
0and10psi).Iftheresetspanischanged,the
minimumandmaximumowsmayneedtobe
readjusted.
Toadjusttheresetspantoanothervalue,performthe
followingsteps:
1. Adjustthethermostattoahigherpressure,
beyondworkingrange(20psiisbest).
2. Aachapressuregaugetothe“G”port(requires
5/32"O.D.tubing).
3. Withasmallat-bladescrewdriver,adjust(coun-
terclockwisetoincrease;clockwisetodecrease)
theresetspancontrol(attheboomofthecon-
troller)untilpressureatthe“G”portequalsthe
desiredresetspanpressure.
3 psig
8 psig
13 psig
Thermostat Pressure
Max. Airflow
Min. Airflow
New Reset Start
Point (3 psig)
Old Reset Start
Point (8 psig)
(Reverse) Reset Start Point Adjusted from 8 to 3 psi
Reset Start Point
Theresetstartpointisthepressurefromthe
thermostatatwhichthecontrollerbeginstoreset
fromtheLOSTATtotheHISTATseing.
ModelsoftheCSC-3000seriescomewithreset
startpointsfactory-setat3,8,or10psi.(Seethe
chartonthenextpage.)Thesearestandardinmost
applicationsandtypicallydonotrequireadjustment.
Ifaresetstartpointisneededotherthanthedefault
seing,allmodelsareeldadjustablebetween0and
10psi.(Iftheresetstartpointischanged,thereset
spanmayneedtobeadjustedaswell.)Toadjustthe
resetstartpoint,carryoutthefollowingsteps:
1. Putthethermostatpressureatthedesiredstart
pointpressure(e.g.,3psi).
2. Removerubberplugatthe“G”portandread
pressureat“G”witha0–30psigauge(requires
5/32"O.D.tubing).
3. Withasmallat-bladescrewdriver,adjust
(counterclockwisetoincrease;clockwiseto
decrease)theresetstartpointcontrol(atthetop
ofthecontroller)untilthepressurereadat“G”
portisjustbeginningtomoveozero(0)psi.
NOTE: Ifthecontrollerdoesnotrespondcorrectly
aeralladjustmentshavebeenmade,it
maybenecessarytocorrecttheresetspan
adjustment.