Best Of

The 26-99 would easily support 3x what you have and is grossly oversized (though would modulate). Even the 15-58 will do nearly double what you have without issue. The Alpha 15-58 and two 3/4" Sentry zone valves would do a heck of a job here but if cost is of any concern, one UPS15-58 on each zone would be a great fit as well.

I typically run my loops 250ft in residential homes and use 32% glycol, and a single 15-58 starts to max out at about 14-15 loops. I do typically use the Alpha 26-99 with zone valves and/or actuators when it's 3 or more zones and 15+ loops, but something like yours would be two UPS 15-58 (if a budget build) or an Alpha 15-58 with two zone valves.

Just to let you know, I have corrected this mistake many times in my career. As I said in my first post, "It may even work in some rare cases." but I have had many situations where baseboard was added to replace a CI radiator that did not heat the space, a Kick Space heater was added to the existing supply and return, and even radiant floor tubing was connected without the proper mixing valve to lower the water temperature as required for radiant floor heating systems. Attempts to do it cheap can often result in undesirable results. If you are going to do this, then do it right the first time. Someone with Hydronics experience should be consulted.

With using the same water temperature on PEX tubing for floor heat, as the CI radiator system, you run the risk of making the floor too hot to stand on. a 165° high limit on a CI radiator might be nice to sit next to on a cold winter evening, but try walking barefoot on a 165° floor. Not so comfortable

@cjjeeper Dm me sir and i will do what i can to help you out