[just_opinion]

I have one cond unit and 2 ID system in my house. But the OD is 2-speed 3 ton compressor and 5 ton double row coil. No check valves -- just LL solenoid valve and TXV

Upstairs is 3 tone evaporator coil with total 560 CFM
Downstairs 2.5 ton coil with total 440 CFM

If one calls -- low speed
If both call -- high speed

works wonderfully.

If you're gonna go overboard for the funzzz, get an inverter board out of the mitsubishi to change the load capacity of your compresor. Hey if it dies you can always have a perfect reason to say "Honey ! Time to upgrade our A/C"

 

[just_opinion]

Just_Opinion-is there any reason you used a 5 ton 2 row condensor unit with a 3 ton compressor? Efficiency-SEER? Someone had brought up that what would happen when the 1.5 ton coil was cooling and the 3 ton wasn't what would happen to the extra refrigerant? Is this why possibly?

Just just want the SEER. I put duck and chicken together to make a soup bowl -- funzz

Heil coil, Lennox compressor, Trane variable speed motor, Lennox blade etc..

I don't know your case will work with 1.5 ton in garage calling with 3 ton pumping capacity. Even though you try to compensate for the larger unit to run half load (I call it half A@#)

You well know that the house is better insulate. Thus garage calls more often and loner runtime and the house may over cool.

I am not worry about not having enough freon coming back to cool the compressor. I worry more about the large coil may freeze if you have running long enough. Or even your duct sweat. My house run about 23-25 delta T.

Hey ! try it out. Worse comes to worse, you put a 1.5 ton condenser out next to the 3 ton. It ain't kill no body. We try to squeeze the dollar

 

[just_opinion]

So just_opnion, probably a couple of 3 ton coils would be easier. Run one or the other. If they both run, run with both in bypass so they split the tonnage.

It is not the coil size to prevent you from freezing