Trane system high humidity

I just built a new 4000sqft home with spay foam insulation in Houston,TX. The indoor humidity was around 80%, very muggy. I found there is a fresh air damper that was set to run 85% of the time. I changed it to 30% and changed the dip switches on the furnace from 400cfm to 350cfm. The humidity is down to 67% and been holding steady there for a few days.

U1 is wired up on the EIM to control the fresh air damper. I would like to use U2 to run dehumidify with AC fan low. Can someone please advise the correct wiring to accomplish this. Its got me a bit confused looking at the schematic because the fresh air damper is already using the BK terminal.

Thanks

My equiptment
4 ton trane 4TTR6048J1000AA
Indoor coil 4TXCD063BC3HCCA
Furnace TUH2C100A9V5VBA

Honeywell EIM
Honeywell zone controller HZ311
Thermostat TH8321R1001

 

BK is connected to the zone controller so not sure how I would connect it to one of the United relays. I set the thermostat to dehum with ac fan low and told it U2 was the relay it was using. Even though it's not connected. Set it at 50% seems to be running at low speed and attempting to remove humidity.