why a brige?

bill millard

I am not sure why to use a bridge with primary , secondary plunbing of a boiler.  Why not just take the loop that needs the hottest water off the primary loop first and then loops needing less heat?  What does the bridge do?

World Plumber

bridge

Dan's book primary/secondary pumping covers it. The bridge and balancing valve allows you to control the flow and temperature through the whole system. Your idea is good. But you may end up with cold water or no pressure differential. when you get to the last zone. I just started to read the design section. It appears there is a science to it. If you want them to work right. But I'm too tired to continue.

DanHolohan

What you're describing is for a one-pipe, primary-secondary system

You'd use the bridge only on a two-pipe, primary-secondary system. The advantage it that every secondary circuit receives the same temperature water. With one-pipe, the water cools from circuit to circuit.