While researching options for a second AC unit for the bedroom of a CF305SK we are thinking of buying I found something that I can't explain.
I found the installation instructions for a Dometic 15k AC unit.
See
http://www.dometic.com/1f24ead8-6316...87ce6bad.fodoc
They show a flow rate of 325CFM. The minimum duct size is to be 1.5-2.5x7-10 inches. I don't know how that compares to Crossroads setup (my unit is at the dealer for a repair) but the next point is interesting, a minimum of 4 registers required and up to 8. My unit has 4 registers, 3 in the living area and 1 in the bedroom. That meets the minimum spec.
But what happens when you tie in a second ac unit to the same ductwork? It seem to me you would be spinning your wheels unless one or both had the trap door (fast cool) open slightly. Just too much airflow for the existing ducts.
This was brought to my attention by looking at another brand of rv with a 15k ac unit. It had 7 ducts in the living area and 1 in the bedroom. It was designed and wired for a second ac unit but the dealer told me the second one would not tie into the duct system???? It would be a stand alone unit only cooling the bedroom. It would tie into the same thermostat but not into the duct.
Maybe that's why I have a hard time cooling my rv when the temp goes over 100. Plenty of ac capacity just no airflow.
Thoughts???