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What is the balancing valve function in Hydronic systems?

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478 views asked Dec 30, 2015 by Devan Talebi

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Balancing Valves. Balancing valves (Circuit Setters) are used to impose artificial head in all pipe routes besides the critical one to prevent short circuiting (excessive flow through lower pressure drop paths that results in insufficient flow through the highest pressure drop path). These valves are usually located on the return side (outlet) of the device as because this subjects their elastomers to lesser extremes of temperature and pressure, extending their lives. The most common type of balancing valve consists of a variable orifice and two pressure taps to measure the pressure differential across the valve. The flow rate is determined by measuring the pressure drop and noting the opening position of the variable orifice. Then a chart is used to find the flow rate.

Another type of balancing valve uses a flow sensor to measure the flow rate, plus some type of throttling valve, impeller trimming, or a variable speed drive to limit the maximum flow rate. This approach is generally more expensive, but has lower pressure drop and reduces pumping energy.

Automatic flow-limiting valves are preferred by some designers. They consist of a spring and variable orifice to limit the flow rate to the maximum intended for that flow path. They are commonly applied on heat pumps.

One apprehension with this type of control device is that there is often no way to measure flow other than to assume that the automatic flow limiting valve is operating properly. There is also no way to adjust the maximum flow rate without replacing the automatic balancing valve. The advantage is that no manual balancing is required if they operate properly and are not fouled by debris in the piping.


There is also a combined balancing valve which includes a shutoff valve.




There are 2 ports which are located on each side of the balancing valve for measuring the input and output flow rate for balancing.

answered Dec 30, 2015 by Devan Talebi

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