HVAC Efficiency Solutions

Are you an operator of HVAC systems? Or are you responsible, as an energy consultant or engineering planner, for optimisation measures or new system designs?
Luftmeister offers a non-binding and free initial assessment of your system – preferably on site, so that all local conditions can be fully taken into account.

On our website, we present a selected range of our solution approaches as illustrative examples.

Efficiency lever: air flow rate 

Air handling systems are operated to supply or extract the required air volumes to and from rooms, halls or technical installations. Depending on the application, it is necessary to:

• supply a room with a minimum air change rate
• prevent explosive atmospheres by providing a minimum purge air flow
• introduce a minimum amount of outdoor air
• safely remove pollutants, etc.

These minimum air flow rates must be maintained at all times. At the same time, they should not be unnecessarily exceeded, as this would result in wasteful operating costs related to:

• fan power consumption
• air treatment, such as heating or cooling

Considering the fact that around two thirds of air handling systems are oversized (by an average of about 15%), it becomes clear that the air flow rate must be controlled within a “green zone” between minimum requirement and waste.

While standard air flow controllers are available for simple round ducts with long, straight inlet sections, practical applications often involve one or more of the following challenges when measuring air flow rates. Luftmeister provides suitable air flow measurement solutions for these cases:

• short inlet sections (downstream of bends, T-joints or other disturbances)
• rectangular air ducts
• very low air velocities (below 2 m/s)
• very high air velocities (above 15 m/s), for example in extraction systems
• contaminated air (dust, oil mist, acidic or alkaline media, solvents, etc.)
• very large ducts with circumferences between 5 and 20 metres
• condensate formation
• high temperatures (up to 1,100 °C)
• requirements for hazardous (Ex) areas
• and more

Fast payback: In most cases, air flow measurement solutions from Luftmeister pay for themselves within 1–2 years by avoiding unnecessary energy waste. At the same time, continuous monitoring of minimum air flow rates creates added value by reliably and verifiably maintaining occupational safety and product quality.

Air balance

Production halls, laboratories and other spaces are supplied with supply air, while air volumes are simultaneously discharged via exhaust air systems or local extraction.
If the supplied and exhausted air volumes are not balanced at all times, either negative pressure or positive pressure will occur. Both situations result in unnecessary operating cost losses: during the heating season, either expensively heated indoor air escapes through doors and other openings (positive pressure), or cold outdoor air is drawn into the building (negative pressure).

The following Luftmeister efficiency solution typically pays for itself within 1–2 years: the air flow rates of supply air, exhaust air and extraction systems are continuously measured and transmitted as signals to the building management system (BMS) or to a compact Luftmeister control unit.
There, a simple control logic is implemented in which extraction and supply air are the leading variables, and the exhaust air flow rate is continuously adjusted to maintain a balanced air balance:

Exhaust air = supply air minus extraction air

In this way, energy waste is permanently eliminated.
It is essential that these air flow rates are measured with sufficient accuracy. For this reason, the approach cannot be based on so-called fan k-factors; see also the section “Unreliable k-factors”.

Air distribution

Industrial air handling systems are rarely adapted to changing requirements. Once planned, installed and commissioned, they usually continue to supply and extract air with the same spatial distribution as at the time of initial operation – even though the hall layout may have been modified several times and machines and workstations are now arranged very differently from the original design.

The result is a combination of areas with over-supply of air (often unnoticed unless strong draughts occur) and areas where production staff express dissatisfaction due to under-supply of air. The latter typically manifests itself in production areas where exhaust air conditions prevail instead of supply air quality.

In theory, the entire system could be redesigned and rebuilt. However, this would be prohibitively expensive – especially since Luftmeister offers a practical and efficient alternative.
As part of a measurement campaign, Luftmeister technicians record the decentralised distribution of supply and exhaust air flow rates throughout the entire production hall. This involves network measurements within the duct distribution system – often accessible only via lifting platforms – or direct air flow measurements at the air outlets.

Based on these measurements, operators are provided with a clear picture of the actual air distribution in relation to the hall layout. In a second step (often immediately afterwards), an air redistribution is achieved by adjusting damper positions. If it becomes apparent that additional air volumes are required at specific locations, the measurements also provide a reliable basis for designing usually minor system extensions.

In short: in most cases, costly supply air is distributed inefficiently. Luftmeister helps to make optimal use of the existing air supply – typically without any modifications to the air handling units or ductwork.
Targeted use of resources – this, too, is HVAC efficiency.

Recirculation air systems 

A large number of installed ventilation systems operate as recirculation air systems. In these systems, a portion of the exhaust air is reused. Instead of being completely discharged as exhaust air to the outside, part of the exhaust air is routed back into the supply air treatment process as so-called recirculated air.

This takes place in the mixing chamber, where recirculated air is mixed with outdoor air before air treatment (heating, cooling, etc.) adjusts the air to the required supply air conditions. The mixing ratio therefore determines the proportion of outdoor air contained in the supply air. This is of significant economic importance, as an excessively high outdoor air fraction results in substantial additional heating costs over the entire heating season.

Experience shows that in more than 90% of cases, recirculation air systems operate with a noticeably excessive outdoor air fraction – leading to additional annual costs in the four- to five-digit range.

The Luftmeister efficiency solution equips both the outdoor air and supply air with precise air flow measurement devices. The measurement signals are continuously transmitted to the building management system (BMS) or to a compact Luftmeister control unit.
There, a simple control logic is implemented: the dampers in the mixing chamber are continuously adjusted until the desired outdoor air fraction matches the actually measured outdoor air fraction. In this way, energy waste is permanently eliminated.

Unreliable k-factors 

A particularly simple and low-cost method for determining the air flow rate of supply or exhaust air systems is to use the differential pressure across the fan inlet nozzle (inlet cone). HVAC equipment manufacturers often provide a printed formula stating that the air flow rate is proportional to the square root of the differential pressure, multiplied by a factor k, which is usually specified numerically.

A similar approach is used with pitot tubes, which are so-called differential pressure devices that convert air flow into a pressure difference. Here, too, corresponding k-factors are specified. The problem is that while the k-factor may be correct on the manufacturer’s test bench, the relationship between pressure drop and air flow rate changes once the HVAC system is connected to the actual ductwork on site.

The same applies to pitot tubes: their k-factors are valid (at best) for long, straight and round ducts. If the measuring location has a shortened inlet section or a rectangular cross-section, significant measurement errors occur.

The Luftmeister solution is as follows: fan inlet nozzles and pitot tubes can generally continue to be used as differential pressure devices. What is crucial, however, is the precise measurement of the differential pressure. If air density varies, these variations must also be measured and compensated. And finally, only precise on-site calibration of the measuring device – usually by means of a duct traverse with a high number of measurement points in accordance with DIN EN ISO 12599 – results in air flow rate accuracies that are significantly better than the commonly encountered double-digit percentage deviations.

HVAC controlling and HVAC key figures

Medium-sized and large HVAC systems generate significant operating costs every year. A key lever for cost reduction is the continuous measurement and control of both central and decentralised air flow rates, adjusting them to what is actually required (see above: Efficiency lever: air flow rate).

In addition, substantial costs arise from air treatment, particularly when no heat recovery system is installed, or when cooling and, in some cases, humidification are used in addition to heating.

This is where Luftmeister provides an effective solution. As part of an HVAC controlling approach, a measurement system is installed that records each individual air treatment stage separately and in detail. In addition to air flow rates, temperatures and humidity, the thermal performance of heat recovery systems, heating, and, where applicable, cooling and humidification is made transparent at all times.

The special feature is that this data is recorded continuously over a meaningful observation period – in some cases for two weeks, in others over an entire year or on a permanent basis. Depending on the application, the measurement system either stores all data internally and is removed and analysed after the evaluation period, or it remains permanently installed and transmits all relevant data to the building management system (BMS).

Luftmeister uses this data basis to identify very specific optimisation measures, which are then communicated to the operator and, if applicable, to their control engineering partner in a clear and implementable form. Optionally, the measurement system can be installed permanently. In this case, it can also be used for continuous improvement controlling and for supplying the relevant air-side measurement data from which meaningful HVAC key figures can be derived – a crucial requirement for energy management in accordance with ISO 50001.

As a result, operating costs are reduced and CO₂ performance indicators are sustainably improved.