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System Installation Guide
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69-2490 —03
Commercial dehumidificationDehumidificationEquipmentOptions:(ISU9000)
• A/CwithLowSpeedFan
• A/CwithHighSpeedFan
• HotGasBypass
• Dehumidifier
WhensetforA/C with Low Speed Fan, A/C with High Speed Fan or Hot Gas
Bypass, therearefivemethodsofdehumidificationcontrol:(ISU9080)See
descriptionsofeach,below.
1 MinimumOnTime
2 HighHumidityComfortReset
3 HighHumidityComfortResetwithMinimumOnTime
4 Reheat
5 ReheatwithMinimumOnTime
1 Minimum On Time(ISU9090):Thisoptionensuresthatthecompressor
runslongenoughtoeffectivelyreducehumiditywhenthecooling
equipmentiscycledon.Thecompressorwillrunfortheminimum "ontime"
you set until the desired humidity level is reached.
2 High Humidity Comfort Reset(ISU9100):Thisoptionusesthecooling
systemtolowerthetemperatureupto5°Fbelowthe currentcoolsetpoint
untilthedesiredhumidityisreached.Thehighhumiditycomfortrangeis
from1°to5°F.
3 High Humidity Comfort Reset with Minimum On Time(ISU9090and
9100):Thismethodusesbothoptionsabovetoreducehumiditywhile
maintainingacomfortabletemperature.
4 Reheat(ISU9080):Thisoptionallowsheatingtorunduring
dehumidificationtohelpmaintainacomfortabletemperature.Ifonlycooling
stage1isused,duringthe"off"cycle,bothcoolingand heatingrunatthe
sametimeasneededtodehumidifywithoutovercooling.Thisoptioncannot
beusedintheHeatmode.Thisoptioniseffectiveonly ifusingasystem
withtheA-Coillocatedbeforetheplenum.
5 Reheat with Minimum On Time(ISU9080and9090)
ThismethodusesbothReheat and Minimum On Timeoptionsaboveto
reach the desired humidity level.
TheDehumidifieroptionrequiresadedicatedunitfordehumidification.Thether-
mostatcanbesettocontroldehumidificationinallmodes(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