Aprilaire 1770A - Page 24

TABLE 9 – Troubleshooting Guide
Symptom Possible Reason Troubleshooting Procedure
Dehumidifier does
not turn on/run.
No power to unit. •Checkthatthedehumidifierispluggedin.
•CheckthatthepowerswitchonthedehumidifierisON.
•Checkthatcontrolknobissettoadrynesslevelnumber.
•Checkthatthecircuitbreakerhasnottripped.The1750Arequiresapproximately8ampsand
the 1770A requires approximately 14 amps.
Dehumidifier blower
is running but little or
no airflow.
Pressure drop across dehumidifier
is higher than 0.8”w.c. (1750A) or
1.5”w.c. (1770A).
•Checkdehumidifierairfilterandwashorreplace.
•Checkforblockedductworkandclear.
•Verifythatthebackflowdamperisinstalledintheoutletductcollarandnottheinletductcollar.
•Checkifbackflowdamperisblockedorstuckandremoveobstruction.
Dehumidifier blower
is running but
compressor is not.
Float switch open. •Iffloatswitchinstalled,checkconnectionsatcontrolboardandemptycondensatepan.
•Ifnofloatswitchinstalled,checkthatthejumperisinstalledatthefloatswitchterminalson
control board.
Coil frosting. •Lackof,orreducedairflow.Check/cleanfilterandcheckforblockedductwork.
•Inletairconditionsbelow60°F.Usethecontrolknobtoturndownthedrynesssetting.
The dehumidifier
damper does not
open in TEST Mode.
Incorrect damper wiring or bad
connection.
•Verifywiringbetweendampersand24VACtransformer.
•IfwiredforTwoZoneoperation,verifythat24VACtransformeris40VAminimum.
•Checkallwiringconnectionsbetweendampersandcontrolboard.
HVAC fan does not
turn on when CYCLE
TIME potentiometer
is turned to TEST.
No power to HVAC equipment. •VerifythereispowertotheHVACequipment.
No power to dehumidifier. •CheckthevoltageacrosstheR&Cterminalsonthedehumidifiercontrolboard.Voltage
should be 18 VAC – 30 VAC.
Incorrect wiring. •Verifywiringandconnectionsbetweenthethermostat,HVAC,anddehumidifier.
HVAC fan operates
continuously after
control knob is
moved out of TEST.
HVAC call or constant fan. •HVACequipmentismakingacall.
•TheHVACfanissettoconstantON.
Dehumidifier air cycling/ventilation
set to constant ON.
•IftheCycleTimeisequaltoorgreaterthantheCyclePeriod,HVACfanoperationwillbe
continuous.
•ReducetheCycleTimeifconstantfanisnotdesired.
The ventilation
damper does not
open when the HVAC
fan is active.
Cycle time met. •ThedamperwillnotopeniftheCycleTimehasalreadybeenmet.
ODT error or inlet air out of
temperature range.
•CheckthattheODTiswiredcorrectlyto
dehumidifier control board and connections are
secure.
•CheckthatODTisinstalledintheoutdoorair
intake according to set-up in Ventilation Section
starting on page 14.
•RemovetheODTleadsfromthedehumidifier
control board and check the resistance. Compare
the reading with the table at right.
Outdoor
Temperature
Resistance
0°F 84,500 OHMS
20°F 46,000 OHMS
40°F 26,000 OHMS
60°F 15,500 OHMS
80°F 9,500 OHMS
100°F 6,000 OHMS
Dehumidifier is not
draining properly.
Drain line or drain trap blocked. •Checkthatthedraintrapisinstalledcorrectly.
•Checkthedraintrapanddrainlineforblockagebyslowlypouringonepintofwaterintothe
dehumidifier drip pan located below the coil.
•Checkdrainlineforcontinuousdownwardslope.
The HVAC fan turns
on unexpectedly.
Sampling or air cycling. •DehumidifierwillturnonHVACfanduringsamplingandasneededtomeetaircyclingor
ventilation requirements as determined by the Cycle Period and Cycle Time.
Dehumidifier is
producing hot air.
Normal function. •Airisreheatedacrossthecondensercoil,resultinginatemperaturerisebetweeninletand
outlet.
TROUBLESHOOTING (CONTINUED)
24