Ill start from the beginning. I went to the customers house there was a leak on the return manifold. I tried to get replacement parts but was unable to... so i replaced the supply and return manifolds. Since doing so the floors dont get warm enough and the kick board heaters(2nd stage) are over heating. I cant seem to get any heat to the floors.

There are 3 zones two of which have 2nd stage kickboard heaters. The system isnt piped primary secondary like i would of liked, the supply and return run out from the boiler first tying into the first kickboard heater then the infloor radiant heat manifolds then to the last kickboard heater to complete the loop.

I have the infloor looped balanced at .75 gallon a minute according to the gauges on the supply manifold, the radiant mixing valve set to 120 degrees. The tubing is 1/2 inch pex

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bad picture but gives you an idea of how its piped. What should the flow rate through the pex to get good heat transfer? Any info would be great thanks