It looks like this documentation on the website describes the screw terminal signals.
The A3 and A4 pins looks like they turn on the dehumidifier, the idea being you can have it run whenever you’re running your AC. The one issue being that it expects a 24VDC signal applied to A3-4. You also need to access the motherboard and turn switch SW1 to the “On” position
| Pin | Name | Description |
|---|---|---|
| A1 | NO: | Normally Open |
| A2 | COM: | Common port |
| A3 | ON-D: | External input (24Vac/DC) |
| A4 | COM: | External input (24Vac/DC) |
| A5 | FLOAT: | External low voltage float switch or water sensor (use normally open switch) |
| A6 | FLOAT: | External low voltage float switch or water sensor (use normally open switch) |
| A7 | VCC: | Humidity transducer “+” |
| A8 | DATA: | Humidity transducer DATA |
| A9 | GND: | Humidity transducer “-” |
Here’s a quick summary of everything else in case that pdf ever goes away
A1 and A2: relay output that closes when dehumidifier is running. Intended to be used to run the furnace/AC fan at the same time. Could be used as an indicator into HA.
A5 and A6: connect a NO switch. Used for a condensate pump to indicate that the pump is broken, water level is too high, and inhibits the dehumidifier from turning on and making the water problem worse.
A7, A8, and A9: The humidity transducer looks to be a input to turn the humidifier into ventilation/air circulation mode when the outside humidity is low and you are bringing in outside air. I’m not sure what type of signal it’s expecting or what the conversion to humidity would be.