System Installation Guide
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69-2490 —03
Commercial dehumidification
DehumidificationEquipmentOptions:(ISU9000)
• A/CwithLowSpeedFan
• A/CwithHighSpeedFan
• HotGasBypass
• Dehumidifier
WhensetforA/C with Low Speed Fan, A/C with High Speed Fan or Hot Gas
Bypass, therearefivemethodsofdehumidificationcontrol:(ISU9080)See
descriptionsofeach,below.
1 MinimumOnTime
2 HighHumidityComfortReset
3 HighHumidityComfortResetwithMinimumOnTime
4 Reheat
5 ReheatwithMinimumOnTime
1 Minimum On Time(ISU9090):Thisoptionensuresthatthecompressor
runslongenoughtoeffectivelyreducehumiditywhenthecooling
equipmentiscycledon.Thecompressorwillrunfortheminimum "ontime"
you set until the desired humidity level is reached.
2 High Humidity Comfort Reset(ISU9100):Thisoptionusesthecooling
systemtolowerthetemperatureupto5°Fbelowthe currentcoolsetpoint
untilthedesiredhumidityisreached.Thehighhumiditycomfortrangeis
from1°to5°F.
3 High Humidity Comfort Reset with Minimum On Time(ISU9090and
9100):Thismethodusesbothoptionsabovetoreducehumiditywhile
maintainingacomfortabletemperature.
4 Reheat(ISU9080):Thisoptionallowsheatingtorunduring
dehumidificationtohelpmaintainacomfortabletemperature.Ifonlycooling
stage1isused,duringthe"off"cycle,bothcoolingand heatingrunatthe
sametimeasneededtodehumidifywithoutovercooling.Thisoptioncannot
beusedintheHeatmode.Thisoptioniseffectiveonly ifusingasystem
withtheA-Coillocatedbeforetheplenum.
5 Reheat with Minimum On Time(ISU9080and9090)
 ThismethodusesbothReheat and Minimum On Timeoptionsaboveto
reach the desired humidity level.
TheDehumidifieroptionrequiresadedicatedunitfordehumidification.Thether-
mostatcanbesettocontroldehumidificationinallmodes(Heat, Off,Cool[ISU
9120]).
Hot Gas Bypass - During a call for dehumidification, the cooling capacity will be used to remove more latent heat
than sensible heat. The operation of Hot Gas Bypass varies by equipment. For more details, contact the equipment
manufacturer.
To see all dehumidification options, press MENU > INSTALLER OPTIONS > VIEW/EDIT CURRENT SETUP >
DEHUMIDIFICATION.
69-2490_B.indd 22 7/13/2011 1:42:01 PM