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What size loops and how long are they. How many loops?

Typically around 1/2 gpm per 1/2" loop 250 -300' max length.

So the number of loops X 1/2 gpm = the total gpm the radiant needs.

Lets assume 10 loops, so a 5 gpm total gpm

With a 2.3 Cv valve flowing 5 gpm, the pressure drop is around 11' head. That is about the high side of flow through that mixer

Here is the Star 21 pump curve. Enter the bottom at 5 gpm, run up to see about 17' head. So you should have plenty of pump for 5 gpm or so. If there is more restriction in the piping, that drives head up, gpm down.

You want to measure the delta after an hour or two of continuous running. The delta will start out wide on a cold system, cold rooms, cold fluid. As the room warms the delta will close up, the load is dropping down. Somewhere in the 10- 15 delta is a common residential design delta. The system may never get to an exact ∆ number you calculate. It's the room load that drives the delta.

Here is the math if you have some accurate numbers looks like this 500 X flow X delta T

So if you are moving 5 gpm 500 X 5 X 30°= 75,000 btu/ hr being transfered to the zones.

As the room warms, delta decreases to say 10° 500 X 5 X 10= 25,000 btu/hr being delivered. Delta dropped due to the room warming, the load decreasing, see the bold printed sentence above.

But really the goal is to satisify that on/ off switch on the wall, the thermostat. If you set it to 70° and the room gets to 70° the job is done. The floors may or may not "feel" warm during this process.

If you have some stable actual data plug it into the formula.

Do you know the heat load of the system in BTU/hr?

Do you know how many gpm is needed to cover the load?

Do you know system head, based on piping loops and mix valve?

Do you have some actual ° readings after running to steady state condition.

Without a few actual pieces of data there is really know way to know if your system is operating properly, satisfactorly?