4 Advice to Choose a Balance Valve

In a recent project, we were tasked with balancing a heating water system with 100 coils. The coils were serving air handling units, fan and coil units, computer room air conditioning units, and terminal units. The building heating water system was equipped with two boilers, two pumps with variable frequency drives (VFD) controlling the system differential pressure, and a Tour & Andersson (TA) (Victaulic) balancing valve installed at each respective coil. The system was designed to solely use the TA valve differential pressure ports for balancing purposes. Major equipment was not equipped with coil entering and leaving test ports, only the terminal unit reheat coils had test ports but were not used because of low design pressure drop and flow.

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Heating Water System Test and Balance

We approached the balance by first presetting the TA balancing valve to 1.0 on the dial to all terminal unit reheat coils with a design pressure drop below 0.75’ WC. The idea was not to set the TA valve below the 1.0 setting to prevent future debris buildup that could create a blockage to flow. These ¾” valves accounted for 65 coils and the remaining 35 valves ranging from ¾” to 2-½” were set to the full open position.

The pump shutoff head was confirmed and verified to match the manufacturer pump curve. The pump total flow was set and initial coils readout was obtained and confirmed to match the pump flow. The next step was to set the design flow at each full open valve using the TA balancing wheel to determine the relationship between flow, pressure drop, and associated valve sizes. Starting with valves on branches that were closest to the pumping system and have higher flow than design. We throttled down a group of valves with higher flow in hopes of gaining flow to the lower ones. Surprisingly, the lower flow ones hardly gained anything! We immediately turned to the product submittal data information and discovered a group of 13 valves were undersized. The number of outstanding valves seemed to be negligible for the heating water system, but the environment they served was considered a critical space.

Balancing Valve Selection

The project team was informed of the situation, but the mechanical contractor refused to accept the fact that those valves were incorrectly selected and installed. The contractor said all balancing valves were installed in relation to the coil pipe size and were selected within the minimum and maximum flow rates. Unfortunately, the product manufacturer has fine print showing the opposite of the contractor’s statement, as follows:

Balancing valves should be sized in accordance with the GPM flows and not in relation to pipeline size. Sizing valves based on the minimum and maximum flow rates is not recommended. Valves should be sized using the nominal flow rates only.

Figure 1 – Manufacturer Valve Selection Guide

It is essential that the contractor understands the difference between the nominal flow rate in relation to the internal design of the valve or to match them with the pipeline size. According to Figure 1, a 14 GPM rated coil would have been selected as a 1-¼” nominal valve size; however, the contractor installed a 3/4” valve to match the equipment coil pipeline fitting at 3/4”. With a 1-¼” nominal valve size selected for replacement, the pipeline fitting would have to be transitioned from ¾” to 1-1/4”. Any mishap in selecting valves can have significant impact on the deliverable timeline and costs for the project. Due to the critical spaces the HVAC equipment served, project schedule constraints, and the lead time of the available valve sizes only three out of thirteen undersized valves were upsized and replaced. The test and balance technicians were then instructed to rebalance the system. After all coil flows were set, the remaining ten undersized valves still did not meet the design flow, as expected.

There were a couple of things noted during that balance. First, we could not further throttle the 65 coils with ¾” valves installed that had a design flow range from 0.5 to 2.0 GPM. These valves were considered oversized based on the manufacturer recommendation and had more flow than expected, even though the valve was set at a 1.0 throttled position. Second, the recorded flow for these 65 coils may not have been that precise because of the low flow conditions. With no other options available, the Engineer of Record (EOR) was brought in to help develop a solution to the balance. After thoroughly reviewing the current balancing methodology and data, the directive was given to add diversity to the system by randomly commanding 30 terminal unit control valves to a full closed position. With the diversity applied, the 10 undersized valves finally achieved their design flow. Once the rebalance was completed, the final differential pressure was recorded and input into the BAS system as a control setpoint for the pumping system.

The balanced condition contributed to a higher cost to operate the system at a higher DP; inversely, operating at a lower DP with the correct valve size installed and no added diversity would have had a lower long-term operating cost.

With the heating water system successfully balanced, the project team at once turned to the chilled water system where similar valve selections and installed conditions were again identified. Seventeen of the thirty-two valves were undersized and eventually, all seventeen were replaced and the chilled water system balance was brief.

Selecting balancing valves may not be part of the TAB scope and/or their specialty; however, TAB agents can develop a test plan, troubleshoot and identify system deficiencies, and work with the Design Team to deliver the most efficient total system balance.

Static Balancing Valve VS Dynamic Differential Pressure Balancing Valve

What is Static Balancing Valve？

The static flow balancing valve is designed for achieving hydraulic balance between different loops in a circulation system, allowing for precise flow regulation in each branch or at each terminal.

The CM system balancing valve also functions as an on/off valve and features a reliable opening degree locking memory device. This ensures that after maintenance, the system returns to its original set state, guaranteeing the proper operation of the circulation system according to the initial design conditions. It provides the most reasonable hot and cold values while minimizing energy consumption.

System Application of Static Balancing Valve:

CM series balancing valves can be widely used in heating and cooling systems, domestic water systems, cold tower circulation systems, dehumidification and other hydraulic circulation systems. It calculates the resistance of the primary main pipeline and each graded pipeline, and then uses a differential pressure gauge to measure and adjust the Kvs value to balance the resistance and distribute the flow.

It is used in conjunction with a differential pressure control valve to stabilize the pressure difference between the supply water and the return water, automatically eliminate the interference of system pressure changes, and keep the pressure difference between the static balancing valve and the differential pressure control valve within a stable value. This ensures that the valve downstream of the return water will not produce overflow or water shortage to achieve the best working state.

Technical Parameters of Static Balancing Valve:

Design standard: GB/T -, BS;

Structural length: GB/T Series 1, EN558-1 Series 1;

Connection flange: GB/T.6, ISO;

Threaded connection standard complies with EN;

Pressure rating: PN10/PN16

Working temperature: -10~120℃;

Comply with PED and valve special equipment manufacturing license

Perform relevant tests in accordance with the requirements of the “Static Balancing Valve Pressure Test Specification”

Installation Instructions and Precautions of Static Balancing Valve：

① The balancing valve should be installed in a location where manual adjustment, pressure difference/flow measurement, and draining are convenient. It can be installed either horizontally or vertically. To ensure more accurate balancing flow, a straight pipe section must be installed at both the upstream and downstream ends of the valve. The required length of the straight pipe is shown in the diagram. The valve must be installed following the flow direction indicated by the arrow on the valve body.

② Before installation, remove the flange sealing cover and ensure there are no debris in the system.

③ Ensure that the flow direction of the medium aligns with the direction marked on the valve body.

④ The valve body installation direction is flexible, and the balancing valve can be installed either on the supply or return pipeline. Only one valve needs to be installed per loop. It is recommended to install the balancing valve on the return pipeline with lower water temperature.

⑤ The balancing valve on the main pipeline should be installed in the direction of the pump outlet. The degree indicator on the handle should face the direction visible to the commissioning personnel for easier adjustment. Ensure that no obstacles are in front of the measurement port on the valve body to avoid obstructing the connection of testing instruments during commissioning.

⑥ Ensure sealing between flanges. The measuring port should be installed before the valve is filled with water.

⑦ Once the valve opening degree is set, do not alter it at will. The balancing valve has a shut-off function, eliminating the need for additional shut-off valves.

⑧ To prevent damage to the pressure test port, it should only be installed after the valve is fully mounted. During installation, follow the principle that the red end is for the supply side, and the blue end is for the return side.

⑨ To ensure proper operation, when CM/25/28 valves are connected to elbows or pumps, a certain length of straight pipe must be kept. When connected to an elbow, follow the 5D rule before the valve and 2D rule after the valve. When connected to a pump, follow the 10D rule. See Diagram 1.

When installing the valve, leave sufficient space for adjustments as shown in Diagram 2 and Diagram 3:

DN15-DN50: H1 > 200mm, H2 > 170mm

DN50-DN150: H1 > 200mm, H2 > 230mm

DN50-DN150: H1 > 200mm, H2 > 400mm

Product Applications of Static Balancing Valve:

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Building HVAC or Heating Networks

In building HVAC and heating systems, in order to meet energy-saving requirements, it is necessary to ensure that all main and branch pipelines meet the designed flow rates. Therefore, balancing valves should be installed on the main, dry, vertical, and branch pipes.

District Heating Networks

District heating networks, typically from a boiler room or heat station supplying heat to multiple buildings, may face uneven flow distribution due to differing distances from the heat source. Without effective equipment to eliminate excess pressure in the shorter loops, the flow distribution will not meet design specifications, causing overheating at the near side and underheating at the far side. Balancing valves should be installed on each dry pipe and branch pipe to ensure balanced flow between each main pipe and building.

Heat Exchange Units or Chillers

When heat exchange units or chillers are installed in parallel, if the flow rates of the units do not match their rated flow, the units cannot operate efficiently. In such cases, balancing valves should be installed on each heat exchange or chiller unit to ensure that each unit operates at the designed flow rate, ensuring safe and normal operation.

Thermal Stations

In systems where thermal power stations or boiler rooms supply hot water or steam to multiple heating stations, balancing valves should be installed on the primary loop side of each heating station to ensure the required flow. Additionally, to guarantee the flow in each secondary loop is maintained at the designed value, balancing valves should also be installed on each secondary loop of the thermal station.

Product Description of Dynamic Differential Pressure Balancing Valve:

The DPCV series dynamic differential pressure balancing valve contains a balancing valve core, high-performance diaphragm, and spring composed of adynamic differential pressure balancing valve component. It is a dynamic differential pressure control valve that ensures constant differential pressure on the load or circuit, helping to provide stable conditions for heating and cooling systems, thereby improving the stability and accuracy of the control valve, extending its service life, reducing noise, and facilitating balance regulation.

Characteristics of Dynamic Differential Pressure Balancing Valve:

Easy to Operate

Set the target differential pressure value through the scale, with simple and intuitive operation.

Stable Accessories

High-performance springs and diaphragms.

Beautiful and Reliable Design

Compact design, easy to install exhaust hole design allows for easy removal of internal air.

Differential Pressure Range Can Be Set

Segmented design of differential pressure control range (high/low-pressure difference models), with higher precision in pressure difference control.

Technical Specifications of Dynamic Differential Pressure Balancing Valve:

Size: DN65-DN250

Pressure rating: PN10/PN16/PN25

Maximum differential pressure: ≤400KPa

Setting control range: 20*-80kPa or 40*-160kPa(*initial setting)

Working Temperature: -10℃ to 120℃

Working medium: Water or neutral liquid, ethylene glycol solution (0-50%)

Surface treatment: Body with epoxy resin coating/spray paint

Length: According to ISO Series 1, BS ,EN558-1

Flange: ISO -2/EN -2

Material:

①Body:Ductile iron EN-GJS-450

②Disc:SS304

③Stem:SS304

④Spring:SS304

⑤O-ring:EPDM

⑥Diaphragm:EPDM+reinforced fiber

Design of Dynamic Differential Pressure Balancing Valve:

The dynamic differential pressure control valve can be used alone or in combination with the static balancing valve. The water few direction must be consistent with the arrow direction of the valve body. The line should be flushed prior to installation and it is recommended to install a filter at the front end. The capillary tube should be connected in the horizontal position of the water supply line, but not under the pipe, to prevent the dust particles blocked, the capillary signal tube must be installed and connected before the water system pressure test, and the blocking valve must be rotated. Otherwise, too much pressure will cause damage to the differential pressure regulator.

The dynamic differential pressure control valve installed valve is installed on the return water pipe, and used with the static balance valve, the static balance valve is installed with the water supply pipe as shown in the following figure.

①inlet pipe

②return pipe

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