Low Temp entering manifold

zmann96

Just got my radiant floor system going . I only have two of the 5 loops complete. I have a heat exchanger from my 75 gal hot water heater. The temp cycles thru heat exchanger at 140 deg with a 8 deg loss going back to hot water tank. my manifold is 8' from my heat exchanger so I have a slight loss, just before my expansion tank about 3' from my circulator I have a temp of 135deg. 3" from the expansion tank heading to circulator I have a temp of 119deg. why do I have a loss at the expansion tank my system is running at 8psi.