Справочник Пользователя для Aprilaire 1770A

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 a minimum of 8 amps and

the 1770A requires a minimum of 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.
• 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 Convertible 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 12 .

• Remove the ODT leads from the dehumidifier

control board and check the resistance . Compare 

the reading with the table at right .

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 .

P.O. Box 1467 • Madison, WI 53701-1467 • Phone: 800/334-6011 • Fax: 608/257-4357 •

10009174   10 .10
B2205271A

Printed in U .S .A .

© 2010 Aprilaire – A division of Research Products Corporation