We installed a new furnace/indoor coil recently. We oversized the coil by 1/2 ton. We put in the piston that that matches the condenser (we think), and our pressures and TD is not working out.

We can only get a 10-12deg TD across the coil, and had to overcharge to get that.

I'm sure my boss will have it worked out by the time I get any answers to this, but what am I looking at?

Thanks