Aprilaire 1750A Installation Instructions Manual page 24

TROUblESHOOTING
TAblE 9 – Troubleshooting Guide
Symptom Possible Reason
Dehumidifier does No power to unit .
not turn on/run .
Dehumidifier blower Pressure drop across dehumidifier
is running but little or is higher than 0 .8"w .c . (1750A) or
no airflow . 1 .5"w .c . (1770A) .
Dehumidifier blower Float switch open .
is running but
compressor is not .
Coil frosting .
The dehumidifier Incorrect damper wiring or bad
damper does not connection .
open in TEST Mode .
HVAC fan does not No power to HVAC equipment .
turn on when CYCLE
No power to dehumidifier .
TIME potentiometer
is turned to TEST .
Incorrect wiring .
HVAC fan operates HVAC call or constant fan .
continuously after
control knob is
Dehumidifier air cycling/ventilation
moved out of TEST .
set to constant ON .
The ventilation Cycle time met .
damper does not
ODT error or inlet air out of
open when the HVAC
temperature range .
fan is active .
Dehumidifier is not Drain line or drain trap blocked .
draining properly .
The HVAC fan turns Sampling or air cycling .
on unexpectedly .
Dehumidifier is Normal function .
producing hot air .
24
(CONTINUED)
Troubleshooting Procedure
• C heck that the dehumidifier is plugged in.
• C heck that the power switch on the dehumidifier is ON.
• C heck that control knob is set to a dryness level number.
• C heck that the circuit breaker has not tripped. The 1750A requires approximately 8 amps and
the 1770A requires approximately 14 amps .
• C heck dehumidifier air filter and wash or replace.
• C heck for blocked duct work and clear.
• V erify that the backflow damper is installed in the outlet duct collar and not the inlet duct collar.
• C heck if back flow damper is blocked or stuck and remove obstruction.
• I f float switch installed, check connections at control board and empty condensate pan.
• I f no float switch installed, check that the jumper is installed at the float switch terminals on
control board .
• L ack of, or reduced airflow. Check/clean filter and check for blocked duct work.
• I nlet air conditions below 60°F. Use the control knob to turn down the dryness setting.
• V erify wiring between dampers and 24 VAC transformer.
• I f wired for Two Zone operation, verify that 24 VAC transformer is 40 VA minimum.
• C heck all wiring connections between dampers and control board.
• V erify there is power to the HVAC equipment.
• C heck the voltage across the R & C terminals on the dehumidifier control board. Voltage
should be 18 VAC – 30 VAC .
• V erify wiring and connections between the thermostat, HVAC, and dehumidifier.
• H VAC equipment is making a call.
• T he HVAC fan is set to constant ON.
• I f the Cycle Time is equal to or greater than the Cycle Period, HVAC fan operation will be
continuous .
• R educe the Cycle Time if constant fan is not desired.
• T he damper will not open if the Cycle Time has already been met.
• C heck that the ODT is wired correctly to
dehumidifier control board and connections are
secure .
• C heck that ODT is installed in the outdoor air
intake according to set-up in Ventilation Section
starting on page 14 .
• R emove the ODT leads from the dehumidifier
control board and check the resistance . Compare
the reading with the table at right .
• C heck that the drain trap is installed correctly.
• C heck the drain trap and drain line for blockage by slowly pouring one pint of water into the
dehumidifier drip pan located below the coil .
• C heck drain line for continuous downward slope.
• D ehumidifier 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 .
• A ir is reheated across the condenser coil, resulting in a temperature rise between inlet and
outlet .
Outdoor
Resistance
Temperature
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