Buffer tank

tc9095

I have a 2 zone radiant system in home I decided to hook up. I started with a Toyo 180 water heater set to 120 and ran a tee out to two Taco007 and return to unit. It short cycled to much. But it worked.

Now I added in a 20 gallon BUFFER tank. I set the thermostat on tank to 150 and it has a Taco007 on heater relay switch from Toyo water heater (in and out on side of buffer tank) then out the top is hot to mixing valve, cold TEE so it has the return from zones cold to tank and cold side of mixing valve. Then the 3/4 line runs to a Taco007 for Zone 1 and a Taco009 Zone 2 (I think prior installer has a 600ft run) so after the water runs through pumps into slab then through check valves and into a 3/4 return line.

My problem, now the fluid never comes back warm. Something stopping cycle...

From picture attached I've added check valves and swapped a 007 for 009