Tom, what size coil do you have? Is it just one loop or two. I am not seeing the heat that you are. Mine is the Hilkoil 24s. Just a single loop, good for 30-60 gal tank. Seems to be keeping the oil fired hot water tank from kicking on but I'm not seeing enough heat out of the kick-space heater. I'm perplexed
Slowed the water down a bit and it seems to be coming out of the coil hotter, have a few more things to try. Last resort I'm gonna reverse the circulator.
Stay warm, Jimmy