Balancing Your Water System without Automatic Balancing Valves

By Marie of Flo-Pac, LLC

Automatic balancing valves offer an excellent way to balance a water system without resorting to setting the system manually. It’s important in any HVAC system to achieve and maintain hydronic balance in order to ensure proper air temperature control in the building.

However, if your system does not feature automatic balancing valves, you will need to configure the balance manually. This is not a difficult task with the right knowledge and tools.

Balancing Your System: The Basic Procedure
A hydronic system is in balance when the flow throughout the entire system corresponds to the flow rate specifications recommended for it. Most experts prefer to balance a water system using direct flow measurements, as it avoids the mistakes usually associated with using pressure drops or temperature changes.
1. Set controls so that the coils are receiving full flow.
2. Adjust the pressure reducing valve, or PRV, so that the system maintains a minimum of 5psi of additional    pressure at the highest terminal. Pressure throughout the rest of the system should be put on the normal setting.
3. Open all manual valves fully and balance the system proportionally.
4. Balance is adequate when water measures within 10% of the flow specifications for the design. If the system does not come to within 10%, you can adjust the impeller diameter.’

If your system utilizes three-way valves, you may need to take additional steps to ensure proper balance. Balancing valve and control valve suppliers recommend closing off water flow through the bypass while water flows through the coil, then doing the opposite (closing off water to the coil while water flows through the bypass). Full flow gpm should be the same through both the bypass and the coil.

Updated: November 23, 2011 — 9:20 am

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