Hi, I was wondering what the best way to set circuit flow is? Should I try for a delta temp of 15 degrees F between supply and return? Are the flow meters on the FN5 manifold accurate? Can I set the flow anytime or should I wait for a hevy load day?

the best way is with math. Heat load calculations, specifically.

Otherwise, do it by comfort.

Thanks Rob Is there a way to figure btu's if I don't know the length or layout of the tubing?

yes, heat load calculations are for the building and the rooms. you won't know your water temperature, perhaps, but it's enough for flow rate and delta-T requirements. of course, that would ideally have been done a long, long time ago.

It may have been done but I picked up the unfinished house from a bank. And the HVAC contractor listed on the building permit is playing dumb.