Flow Design Michigan, Automatic Balance Valves, Manual Balance Valves, Pressure Compensating Valves, Flow Limiting Device,
5975 Dixie Hwy
Saginaw, Michigan   48601
Phone        1.989.746.0700
Fax             1.989.746.0777
Link onto the Flow Design Inc Logo above for more information.
The DA 516 is a differential pressure
controller that is adjustable. Its function is to
keep a constant differential pressure over
the load (a branch of several fan coils, for
example), regardless of pressure variations
in other parts of the distribution system. The
DA 516 will control the pressure between
the controller itself and another point in the
system, the pressure of which is transmitted
to the controller through a capillary tube. The
controlled pressure set point is adjustable
within a specified range. Because it
provides a self adjusting restriction, the DA
is well-suited to variable speed pumping
Designed specifically for terminal
applications including fan coils, VAV
boxes and heat pumps, the TBV-C is the
perfect combination of functionality, size
and value. The compact TBV-C combines
in one valve both balancing and control
functionality, saving both field connections
and field labor time. In addition, the TBV-C
has shut-off functionality, eliminating the
need for a separate shut-off valve such as
a ball valve, again saving field
components and connections. The TBV-C
ships with a factory installed on-off
actuator, plus pressure and temperature
ports to allow easy flow measurement for
system balancing and calibration.
2 Way Manual Coil Package Template
2 - Way Automatic Coil Package Template
3 - Way Manual Coil Package Template
3 - Way Automatic Coil Package Template
Click on the template below for PDF to edit specific to job
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Solving Balance Issues with A Differential Pressure Controller
February 10, 2016   

What are your options when unbalanced circuits in an existing hydronic system are creating comfort issues due to underflow or overflow through coils?  

The short answer is yes; however, they aren’t always affordable or even practical.  Try finding locations for automatic flow controllers or pressure independent
control valves at every terminal unit in a 20-story office building and you’ll see what we mean.  Fortunately, many of these problems can be addressed in stages, by
installing adjustable differential pressure (DP) controllers on problem circuit(s).

What Does a DP Controller Do?

Pressure fluctuations are an inherent part of every hydronic HVAC system.   If these pressure fluctuations are not addressed, they will most certainly create an
imbalance in flow. This commonly occurs in large systems where one circuit, riser or wing of a building is located far away from the pump.  As a result, distant coil
(s) may be starved of flow under full load conditions, with the majority of the flow occurring at the nearby coils. Or, if flow limiters are installed on distant circuits,
pumps may ramp back so much during low demand periods that the closest circuits get starved.  In either case, you’ve got a problem.

DP controllers stabilize these pressure fluctuations and can be installed where they are needed with very little disruption to the system.  They operate to maintain a
constant differential pressure over the load (a branch of several fan coils, for example).

The DP controls the pressure between the controller itself and another point in the system from which the pressure is transmitted to the controller though a capillary
tube. (Figure 1)

Figure 1

In a typical system, the DP controller would be installed on the return side of the circuit (most likely the one closest to the pump) and would be linked by a capillary
tube back to a Venturi upstream of the coil(s).  The DP controller absorbs excess differential pressure between the location where it is installed and the upstream
location where the capillary pipe/tube is connected.  This allows the differential pressure across the circuit load to remain constant so the control valves can
effectively operate over their respective control range.

The beauty of this solution is that it allows for simple and systematic problem solving.  One circuit can be fixed without disruption of other circuits because the
installation of the DP controller and Venturi effectively isolates it from the other circuits.
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