Fullham Reach

Precise commissioning of hydronic balancing valves optimizes their performance. Paul Wightman, product development manager explains

Optimal performance of water-based low temperature hot water (LTHW) central heating and chilled water cooling (CHW) systems derive from two critical actions – correct design and accurate control. However, it is the commissioning engineer who is responsible for determining the right comfort levels and effective temperature control all year round in commercial buildings,

LTHW and CHW pipe networks in public spaces such as offices, apartment blocks, retail and hotels come under a great deal of stress, with many variants potentially compromising their smooth operation. For example, heating and cooling systems in commercial buildings must be designed to accommodate the high volume and varied movement of people, use of electronics and other external factors such as open windows and doors.

In everyday working environments, poor temperature regulation can have an undesirable impact on the performance of building occupants. In order to promote a comfortable environment, I suggest your focus, as a building service engineer, should be on effective balance and control.

In engineering terms ‘T set’ is the desired area or room temperature for the people or equipment at a location 24 hours a day, 365 days a year. In other words, optimum performance is determined by 100% temperature control throughout the day for the whole year. When control temperature swings become too great, this typically indicates overheating or under cooling and energy wastage.

However, a well-balanced variable volume system can only be realised by employing the right set of hydronic balancing valves (also known as commissioning valves). The correct circulation flow rate throughout the whole system needs to occur irrespective of any central or localised pressure changes. During partial system loads, differential pressure changes inevitably occur during a significant proportion of any UK building’s operational life because of our mild climate.

Lower operational building loads are a great opportunity for renewables, lower carbon energy or lower grade energy sources. This means enhanced energy savings are possible, but only when these alternative energy sources are integrated effectively with both good building design and commissioning.

Incorrect hydronic balancing of a LTHW or CHW water-based commissioned system causes unequal distribution of the flow. This will result in surpluses in some terminals and undersupply in others, reducing comfort control quality and the desired heating or cooling will not be forthcoming in every part of the installation.

I suggest a solution may be using the appropriate mix of hydronic balancing valves including differential pressure control valves (DPCVs), pressure independent control valves (PICVs) and thermal balance valves (TBVs). These have repeatedly proved extremely efficient in helping to stabilise comfort and temperature control while also contributing to flexibility and simplifying the commissioning procedure.

A DPCV is set to maintain a steady differential pressure under dynamic balancing conditions, ensuring flow cannot exceed a desired rate. It therefore helps reduce both energy consumption and the risk of noisy vibrating pipes, while also allowing commissioning to focus on one circuit at a time.

Self-regulating valves open and close directly in response to changes in the physical environment locally, while control valves require an external input to regulate. This creates a risk that external factors could delay or prevent the control signal happening.

A DPCV regulator typically applies the pressure of the controlled flow medium (water) against a diaphragm. This diaphragm then opposes a compressed spring to achieve force balance with the diaphragm at a given set pressure. Any change in the controlled pressure causes the diaphragm to move, which causes the flow area of the regulator to change, so adjusting the controlled opening of the valve.

For optimal energy efficiency and comfort control, differential pressure valves should be used as close to the output terminals as possible. However, pragmatism and cost-effectiveness dictates these may be installed within network branches and sub-branches then using balancing valves and control valves downstream to maintain delivery.

The DPCV is often called a ‘dynamic balancing valve’ because it is constantly adjusting to the system and maintaining its set-point position, so it is ‘moving’ in response to its own feedback.

PICVs are also self-regulating as they maintain control in exactly the same way as a DPCV, dynamically to the system. However, they also have a control actuator fitted that allows the building services control system to interact and adjust its output to any changing system requirements.

Having a control actuator input is not unique to the PICV; any control valve has this feature. However, a PICV improves the regulation performance of itself in relation to the circulatory system and this benefits delivery performance, energy efficiency and comfort. PICVs combine several valve functions excellently to enable very cost-effective optimised control, while also simplifying the commissioning process.

If you have any questions regarding hydronic balancing valves you can contact me at paul.wightman@brymec.com

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