The continuing saga.
The copper lines are now silver-soldered on.
Note: on a Sunday evening, it's dammit hard to find real silver solder. And the guys that they've got answering the phone at Lowe's and Home Depot will tell you that they have it, 4 oz for $13. Given that silver is currently sitting at $34.84/Troy ounce, that didn't make sense. "I mean elemental silver! Ag!" I growled into the phone. "Comes in sticks, not rolls of wire!" They insisted that it was silver (in color, I'll grant), and that I should make the 20 mile drive to get it.
I texted an AC man that I know, and offered him double price for 5 sticks of silver solder. 20 minutes later, I was handing him $40 for five little sticks.
We barely got it done before the rain hit. This is good, because silver solder doesn't like water, when you're asking it to stick to copper.
I got the plennum adaptor built out of that aluminized foam board stuff. It seems too cheap and flimsy to do any good, but it's easy to cut in the shape that you need (in this case, a weird prism with a turn in it, to go from the AC cabinet to an off-centered (in two axises) plenum sticking out of the ceiling), and it stiffens right up with the application of enough aluminum tape. And really, it only has to withstand the stress of air moving through it, and some temperature gradients. The board actually has some R value to it.
I'm not very good at this, but I will say one thing-- every bit of air that flows through this system is going through that filterbox first. I caulked every joint (filterbox to new false floor, false floor to walls, filterbox to furnace, furnace to AC coil box) before using rolls of alluminum tape.
I'm about $2600 in, but I think that all the costs are sunk.
Today we pump out the lines with a vacuum pump for an hour and a half, and if they hold a vacuum, we'll charge them with the 13.5 lbs of super-duper new freon that the outside Puron unit is precharged with . Then we'll hook up the power and thermostat wires, and see if this thing will run.