Hydronic Balancing Part 9: Why Can’t Circuit Setters Be Pre-Set for Proportional Balance?

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By Chad Edmondson

In our last blog we covered (in detail!) the step-by-step process of proportionately balancing a hydronic system.  But many of you may be wondering if all that legwork is truly necessary when theoretically the engineer has all of the information needed to tell the installing contractor exactly where to set those circuit setters to achieve proportional flow.  After all, it’s easy enough for the engineer to determine the pressure drop through each circuit by using the System Syzer and come up with the correct setting for the circuit setter so the flow is automatically balanced and the last circuit setter is wide open.  We discussed how to use the System Syzer in Part 3 of this hydronic balancing series.

So is the balancing process described in Part 8 really necessary in a system set up for manual balancing with circuit setters?  The unfortunate truth is yes, it is.

Here’s why:  Systems rarely get installed exactly as they were drawn on the plans, and any calculations the engineers perform in advance are based on specific equipment, specific lengths of pipe, specific numbers of elbows, etc. as show on the plans.  If any of these change (and they always do) the pressure drop and flow to the individual circuits changes also.  Therefore there truly is no way to guarantee a proportionately balanced system without the hands-on method described in the previous blog.

How can an owner or general contractor be certain the mechanical contractor has done his or her due diligence by systematically balancing each zone? Ask to see the critical circuit and then verify that the circuit setter at that location is wide open.  If it isn’t, then the system isn’t proportionately balanced for maximum energy efficiency – and it does not meet ASHRAE 90.1 which states:  Hydronic systems shall be proportionately balanced in a manner to first minimize throttling losses; then the pump impeller shall be trimmed or pump speed shall be adjusted to meet design flow conditions.