Repipe hydronic mains

[Revprop]

I have 1600sqft 3 bedroom Cape in Hartford, CT with a converted gravity system. 100,000 BTU WM WSO-3 boiler with Taco 007 circ pump (return side), 3/4" system bypass and separate zone for indirect HW. The 1st floor has wall type CI radiators with 53,000 BTU total (8 rads), the 2nd floor has free standing tube style CI radiators 33,000 BTU total (4 rads). It's a 2-pipe direct return layout. Near boiler piping is 1" cu, old mains are 3" pipe stepping down to 3/4" pipe, feeds to all radiators are 3/4" pipe and are convienently accessible in the basement. Boiler is set to 195F. No TRVs installed on any rads. The system seems to work o.k.

I'm going to finish the basement and want to do the following:

1) Repipe the old gravity mains with 1" and 3/4" copper to get a clean ceiling.
2) Split the 1st/2nd floor into 2 zones. I plan on 1" copper for the 1st floor and 3/4" copper for the 2nd floor. Also, convert to 2-pipe reverse return.
3) Install a new 1/2" zone for 450sqft basement using baseboard - probably around 6000 BTU (10 ft).

I had planned to use a single circulator (existing TACO 007) with high Cv White Rogers 1311 zone valves and B&G Thermoflo balancers. Also, I was going to install a differential bypass valve in the system bypass line.

Two questions:
a) Does this system seem reasonable? I have done some homework and believe the BTU/pipe size etc should be O.K, but would appreciate another opinion. Are the Thermoflo balancers overkill?
b) Do I need any other bypass to protect the boiler? Should I have a separate bypass to ensure adquate boiler return temp and install this before the zone value manifold and differential bypass line?

Thanks for any comments/help.

[nhmaster]

Yea, the re-pipe will be fine. Essentially all that 3" pipe is doing is holding volume that you don't need anyway. As for the bypass, it's easier to do it now rather than later. I typically use a 3/4" copper line with a ball valve to adjust the flow and a temp gauge.

[Revprop]

Great - thanks for your input. I'll plumb in the additional bypass as suggested.

Thanks again.