Well from specs type M copper will be slightly bigger than 1" ID, something like 1.055, the pex ran thru the basement now has an ID of .865 according to my slide caliper.
Doesn't sound like a big difference but when using the circulator chart from Taco that .135 makes a big difference even though there is roughly only seventy feet of that smaller pex in the basement. Once I get the new wood boiler built I'm sure I'll be upgrading pumps and want enough flow to stay as close as possible to that magical 20 degree delta T even with a call for heat, hot water and melting snow at the same time.
I ran into the same thing in the shop, either buy expensive circulators and use 1" pex or goto 1 1/4"pex and smaller circulators, was more cost efficient given the relatively small difference in price of the pex to go with 1 1/4".
I'll have at most 12 long radius 90's in the basement. I'm sure Tacos chart is assuming 90's are the standard short radius like used in domestic plumbing. If the radius is long enough on them shouldn't be anymore restriction that a straight piece of pipe.
Kinda funny though, will be changing pex out for copper in the heating system and then later redoing all the domestic plumbing with pex. Have a real mishmash of stuff in the basement now. Have CPVC, galvanized and a few pieces of what I'm sure is leaded pipe yet. Just going to start all over from where the well enters on.