Second ac unit

Depends. Most are not tied into the ducts. Some will be wired thru the thermostat, but again dont bet on it.

Mine is tied together and has adjustable vents. Fleetwood.

My guess is a 2018 will have common ducts. Do you have a zone button on your thermostat ?

If so I’ll bet it’s wired.

You could ask your dealer or call the factory.

You would need to have that custom done.
If you ask for it from the factory, the second would be a unit all by itself with the controls built into the overhead unit and the air just coming out of it.
We just ordered and got a 37 footer with the second one as I describe above.

Jack L

Ours is separate and vents directly into the RV.

Our bedroom AC does not connect to the ducts. I cut a hole above the bedroom door and added a fan to come on when the bedroom AC does to force some air into the living area. Works good here in South Florida.

We just got a new Grand Design and ordered it with a second AC. The second/bedroom AC is not ducted and has its own thermostat. We haven't had to use them yet (other than to make sure they work), but both ACs are 15K, so I'm sure they will do the job.

The second AC location in most trailers I've seen is not ducted. If your trailer is built like this then all isn't lost. Sometimes just having a second AC running is enough to cool the dead spots though natural air movements. Works well on days when it's not searing hot. A helper fan works well on those really hot days as it helps to speed up the mixing of air.

If your second AC location isn't ducted, don't waste the time trying to tie it into the ductwork. If there's not a duct for a second AC then the ducts are probably sized to take the airflow from only one unit. If you were to add another unit to this system then the efficiency of each unit would go down as the two units compete against each other to occupy the limited amount of space. In the end, you don't really get to take advantage of the additional cooling capacity.

I can a) dump my front unit from the bottom or b) use the existing ductwork and run a floor fan in back under the a/c blowing to the front (quieter). Either way, I stay pretty comfy into the triple digits.

Thanks for the input, I think we are going to add the second unit and block off the two vents that feed into our master bedroom and bath, and if my thinking is right it should redirect more airflow to the remaining vents in the TT.