Troubleshooting Defrost Switch; Verifying Capacity - Aprilaire 1730A Troubleshooting Manual

6. Turn ON/OFF switch ON and wait for the amber COMPR LED to light (after 3 minutes of
dehumidifier fan run time).
7. Measure the voltage between the COMPR BRN and NTRL ORG terminals on the control
board.
a. The voltage should be between 103.5 – 126.5VAC. If the voltage is correct, move
to the next step.
b. If the voltage is not within this range, replace the control board assembly (4923
or 5329, see parts list on pg. 15).
8. Turn the dehumidifier OFF and unplug.
9. Disconnect the compressor overload switch by removing the orange wire from the
overload switch (A) and brown jumper wire from switch to compressor terminal (D).
10. Measure the resistance across the switch.
a. The resistance should be close to zero. If the resistance is correct, move to the
next step.
b. If it is not, replace the overload switch (5324).
11. Disconnect all three wires from the run capacitor. Measure the capacitance across the
poles.
a. The capacitance should be between 52.25 – 55.75µF. If the capacitance is
correct a compressor winding is open, dehumidifier will need to be replaced.
b. If the capacitance is not within this range, replace the 55µF capacitor (4922).

Troubleshooting Defrost Switch

1. Remove the frost switch leads from the control board.
2. Verify continuity (resistance near zero) between the two defrost switch leads. If there
is no continuity, the switch (4925) will need to be replaced.

Verifying Capacity

If the unit is functioning properly, and there are no fault codes present, this procedure can be
used if there is concern that the dehumidifier is not removing sufficient moisture. After the
dehumidifier reaches stable operating conditions (approximately 20 minutes), measure the
inlet air temperature and RH and compare it to the outlet air temperature and RH. Use the
graphs provided to convert the inlet and outlet air conditions to air moisture content to
calculate if the moisture being removed is near the performance levels shown in the table on
page 13. If the inlet air conditions are not within those listed on the table, contact Aprilaire
Technical Support Monday through Friday from 7:00 a.m. to 5:00 p.m. CST at (800) 334-6011
for assistance in determining performance. The dehumidifier will not remove moisture if the
humidity of the inlet air is less than 40% or the dew point of the inlet air is 40°F or lower.
1. Verify that the damper in the outlet collar of the dehumidifier opens/closes freely.
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