From my previous research, it is the Dometic HP A/C line. I couldn't find a manual either.
I recently worked quite a bit on the main ducted unit and increased it's performance. Few things I did,
- Put a new A/C seal on & fixed stripped front lag screw holes. This unit is extremely "rear heavy" which puts quite a bit of upwards pressure on the front lag screws on the A/C unit. My screw holes were stripped, and the A/C seal was deformed. I added a new A/C seal, along with epoxy/metal inserts in the screw holes, along with foam "supports" under the rear of the A/C to support the weight.
- Added a "V" deflector made out of aluminum flashing to the main plenum under the A/C unit. As you'll see, the plenum is a square box with 2 rectangular openings on each end for the air to flow through. The "V" deflector directs air towards these opening, eliminating most of the plenum, and in theory, smoothing out the air flow. I basically just took ~10" wide flashing, and folded it in half, then installed it so half the air goes to one side, and half to the other.
- Sealed up ducting just outside plenum. Stuck my head in there with a flashlight, and 2 of the ducts were dislodged and allowing air to simply flow into the ceiling.
- Sealed up ducting in all the vent holes inside. This helped quite a bit.
- Make sure to manually control fan speed on the thermostat. Many times when it is on Auto, it will run on low. Switching to high makes quite a difference.
I've got some 5" close-able vents on order as well to help direct the air flow.
All in all, it has helped, but I'm still considering adding a 3rd A/C to the garage to help take the load off the main unit.
