John,
I have a T4 on my chiller closed loop. I also tried it as a return pump for a bit, replacing my MAK4, flow was about 10% less with approx 5' of head. Also tried it on my ETSS800, dual down draft, but the flow was not even close to what it needed.
From what I have found on the web for numbers the T3 may be the pressure version and the T4 for flow. I'm thinking of getting a T3 to try and see what it can do.
The T4 pump was very close to my LG 4MDXQC. From all the pumps I have had, I made a excel file with my tested/estimated pump curves. I'm just not sure if a T3 or T4 will be enough. Please let me know.
Link
Lee