Thermostat choices with Taco SR502

[Baldrick]

This is a last piece in my puzzle.

2 zones:
- high temp underfloor
- low temp slab

1 primary pump, 2 secondary pumps (one with I-series setpoint mixing valve), Trinity Ti100 w/ Sentry 2100 control, Taco SR502 switching relay).

There already is one thermostat in a slab zone (it does central air heating and cooling). I am not sure if there is a thermostat that would do all in one (3 sources: central air HAC + radiant H) or I should just add on another dedicated heating only thermostat?

Second zone thermostat would do radiant only.

Any suggestions? Tekmar? Honeywell?

[jadnashua]

Radiant heating can use either the air temperature or the floor, but you would not want to use the floor temperature to control the a/c. Other than that, I'm out of my element!

[Baldrick]

Radiant heating can use either the air temperature or the floor, but you would not want to use the floor temperature to control the a/c. Other than that, I'm out of my element!

It's too late in the game to add slab sensors so it will be air sensing.

I've read mixed opinions on dual-stage heating thermostats (is that the right name?). And I am not sure if they would work here.

I want radiant to have priority for heating and have furnace kick on only at ~50F (in case boiler fails) or when humidifier calls for fan.
That's the first floor. Second floor would be radiant heat call only.

So far I found Tekmar Nt 545 as candidate for 2-stage and Tekmar Nt 541 (or 542, but I am not sure if I need another progammable or 545 would program both zones) for single stage in second zone.

Still have to check out the Honeywell.

Would I need any additional controls with 545 and 541 or they would wire up directly to Taco SR502? Or is there a better way?