Balanced Circuit Lengths

Q: In a hydronic system, should I keep all of the circuit lengths the same?

A: Most of the time, yes.

There are differing opinions on the need to keep balanced circuit lengths when designing and installing a hydronic system. The primary goal in any hydronic zone is to keep the flows of all the individual circuits the same, thereby creating equal temperature drops and equal heat from each circuit.

In the olden days, prior to circulators, gravity fed hydronic systems were sized in such a way that the natural balance of the system dictated the flow. These systems were very complicated to design and install, but were (in theory) self-balancing and required little to no adjustment.

With the introduction of modern hydronic circulators and flow controls, the systems became much more forgiving to design flaws. Circuits of varying lengths can be mated to a single manifold with flow controls, then balanced out to provide equal flows throughout the system. However, there is a tradeoff: balancing the systems can add a significant labor cost to both installation and maintenance. This may not be a huge deal with a single zone or 2-3 circuits, but with larger zones and more circuits, this becomes quite the daunting task for the installer. Also, if you're using a single manifold with actuators to feed multiple zones, having equal circuit lengths may not apply.

Do circuits need to be the same length? Technically, no. However, when a system is designed and installed with equal length circuits, the payoff is a more stable, self-balancing system that will require less maintenance and adjustment over it's lifespan.

-MDR