How To Regulate Everhot Pex Manifold

[gurumanjohn]

I just installed an Everhot Pex manifold that's supplying a 250 ft loop heating the floor of my greenhouse. We're having trouble getting a good flow through the manifold, although when we disconnect the supply line, the flow is pretty good.

The everhot site mentions that flow and balancing can be done by using both the adjustment valves on the return side AND the flow valves on the supply side of the manifold. But there are no instructions on how to do that. Can anyone help me to understand how? It's not clear whether screwing the return side control down tight or loosening it increases the flow. It's also not clear how, if at all, the flow gauge can control the flow rather than just measure it.

Also, the air valve mounted on the manifold doesn't seem to be effective in purging air. Is it just inadequate or may there be something wrong with it?

Thanks.