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
