I have a small staple up under floor radiant heating system.
Right now 8 zone manifold that I am using 5 zones, will be adding 3 more zones in the near future.
I am running supply temp of 140deg F (it actually runs at 137 / 138deg F)
The return temp is between 126 and 128deg F, so it runs between 8 to 10deg F cooler.
Is this a good ratio?

Thanks for any info.