Need Expert feedback/opinion on 3 zone radiant heat setup

Hello,

I'm in the planning stages of my 3-zone radiant heating project and I'm looking for any input / critique of the set up I'm about to build. I have attached a schematic to this post detailing the layout.

This heat supply is supplementary to forced air heat in the house. (It is not the main source of heating the house)

In summary:

The main loop will be serviced by an IBC combi boiler which is already installed. The boiler has a separate pass-through circuit for instant hot water. This is already hooked up to service the house needs and is not included in the attached diagram. The second 'heat circuit' in the boiler allows for a closed loop radiant heat. There is a safety heat purge valve on the boiler built into this circuit along with an internal pump that is activated by the boiler whenever there is a call for heat on this circuit. This will be the main water circuit as per attached diagram and will be 1 inch in diameter. On this circuit, there will be a fill connection and an expansion tank. A microbubble air eliminator will also be installed.

Off the main circuit there will be 3 heating zones. Each zone supply and return will be connected by closely spaced tees, which will connect the 1 inch pipe into 3/4 inch pipes in each zone. (The manifolds will distribute into 1/2 inch pipe heating loops). As per IBC documentation, these will be "closely spaced tees are maximum
four primary circuit piping diameters apart, with a minimum of eight pipe diameters of
straight tubing upstream of first tee and a minimum four pipe diameters straight
tubing downstream of second tee.

Each zone will also have a thermostatic mixing valve and a 120 v pump with a built-in check valve. The pumps will be switched on/off by a 3 zone Taco switching relay. If an zone thermostat will call for heat, that zone pump will be activated along with the boiler main heating circuit as per diagram.

Zone 1: Garage radiant floor
-thermostat for this zone will be mounted on the wall in the garage, since room temperature will be the 'deciding factor'

Zone 2: Bathroom towel racks
-thermostat will be activated by a temperature probe directly behind the return manifold, since towel rack temperature will be the 'deciding factor'
Question 1: Any suggestions of a specific 'temperature probe' that can be used here to 'close the loop' on this zone's thermostat?
Question 2: Any suggestions of a specific thermostat (brand / model) to use with a temperature probe?

Zone 3: Basement radiant floor
-thermostat will likely be wall mounted in the basement, since the basement is colder than the upstairs of the house. The other option is to also use a 'temperature probe' here to 'close the thermostat loop'
Question 3: Looking on feedback on whether the thermostat should be activated by ambient air temperature in the basement or via temperature probe of the water in the basement loops (like in zone 2)?


Any feedback and suggestions are greatly appreciated. (Once the design is finalized and I embark on building this setup, I will update this post with photos.)

Thank you for your help in advance.