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Save air – adjust your ventilation to the demand

Nowadays it is standard practice that the central heating is adjustable and every heater is fitted with a thermostatic valve for adjusting heating to the variable heat demand in a given room. In the case of ventilation it is no longer that obvious. And after all, adjusting ventilation to the demand may bring some major savings in respect to the building operation as well.

A standard mechanical ventilation system usually includes control dampers or CAV regulators, and supplies a constant amount of external air calculated on the basis of the maximum potential number of people who may stay in the room. Usually it is the value of 30 m3/h multiplied by the number of chairs designed by the architect (currently, while PN-83/B-03430/Az3 standard has been withdrawn, there is no set air stream value that should be supplied per every person present in the room. However, according to different sources, this number fluctuates around the value of 30 m3/h mentioned above or more). Such a system constantly supplies the same amount of air to the room, regardless of the number of people. During winter and the transitional season, the air is heated. And if there are any display monitors in the rooms – it has to be humidified. On the other hand, in summer the air is usually cooled down. This kind of processing consumes a lot of energy.

Save energy – reduce the amount of air supplied to empty rooms

If the number of people in the room changes significantly during the day, it is worth making it possible to reduce of the amount of supplied air. When it is not necessary, there is no need for ventilation at the maximum flowrate. Less air means lower resistance in the ducting network and in the air handling unit components. The use of inverter controlled fans (current Technical Specifications – §148.5 – require each fan to be adjusted to a capacity change) translates into significant energy savings. Energy is also saved due to reduced coolness generation in summer and humidifying steam generation in winter. The thermal energy demand also gets lower. Reduced average airflow during a given time period also means savings in the air filters wear and tear. The filters are one of the basic elements of air handling units and must be replaced periodically. 

In order to decrease the amount of supplied air, every duct (supply and exhaust) handling a single room should be fitted with a VAV (Variable Air Volume) regulator. Independently of the pressure distribution in the system, the regulator keeps the set airflow value constant. This value may be made dependent on the CO2 concentration in the room, which is directly proportional to the number of people present. The less people, the smaller the external air demand. However, it should be kept in mind that all bypasses must be fitted with regulators. If you want to keep the air volume value constant (in utility space, storerooms, toilets), VAV regulators should be replaced with CAV (Constant Air Volume) regulators. They mechanically (without electricity) keep the airflow constant, regardless of the varying conditions in the system.  

The diagram below shows the differences between the set value being kept with 3 straight segments before the device and without those segments.

Wide range regulators – greater possibilities

The best regulators for the ventilation system under discussion are the ones with a wide regulation range and operating at low airflow speeds. Lower air flow speed means smaller noise generated by the device, which translates into decreased size of silencers at the system ends, where there is often little space for such devices. In the case of smaller systems with symmetrical ducting network distribution and a properly selected regulator (maximum throttling not exceeding 50 Pa), one can completely remove the silencers. RVL-R is a new regulator by SMAY, which fully meets all the requirements mentioned above. It operates at speeds within the range of 0.45 – 5 m/s and it does not require straight segments before and after the regulator.

analiza-cfd_zwezka-venturiego

The device has a very wide operating range – the minimum rate makes only 10% of the maximum airflow.

Please notice that both the shape of the reducer (measuring element) and the position and form of the baffle are selected to make an accurate measurement possible, irrespectively of the presence of straight segments. It has been confirmed by CFD analyses and measurements taken on standardized stations approved by ITB – the only body in Poland entitled to issue the National Technical Assessments (NTAs) and to verify the correctness of submitted reports and the results they contain. 

The structure of the iFlow system.

Individual room arrangement is the future

In connection with the iFlow system (Individual Ventilation System made by SMAY) the RVL-R regulator is perfectly suitable for reducing the amount of supplied air depending on the number of people in the room. Apart from the regulators described above, the system is fitted with CO2 concentration sensors integrated with a temperature sensor, motion detectors and a central control unit. The CO2 detector, as mentioned above, reduces the amount of supplied air. When there is no activity in the room, the motion detectors decrease the airflow rate down to the minimum ventilation flow designed. It is also possible to use a calendar to set the system operating hours (for example CO2-dependent), standby time (which means smaller expenses), aeration and many other functions available through the web server. The system is user friendly, both for administrators and regular users who are able to change the air parameters within the given room. Apart from the reduction of supply air in all rooms, the system aims for full (or maximum possible) opening of the regulator dampers, which translates into maximum possible decrease of the fan rotational speed. This operation results in optimal energy consumption by fan motors. A smaller air flow also means longer lifetime of air filters, and therefore – real savings.

Adjust your construction business to the European market

Directive (EU) 2018/844 introduced changes in the existing EPBD and EED directives. In general, the changes are directed towards the technical infrastructure automation with the aim to improve the environmental conditions inside rooms and to optimize the energy consumption – to lessen the impact on the environment. The iFlow system perfectly fits the new trends. It saves electrical and thermal energy while maintaining the users’ comfort. And getting with the times, it is possible to control the system by a mobile application, so users can literally operate it without moving a muscle. For more information about the possibilities associated with the system see the Installer Manual and Designer Guide Book (both available on our website, in the Designer Zone and Learn tabs).

Author
Michał Cisowski

VAV Systems Manager – SMAY

systemów bezpieczeństwa
Szymon Płonczyński

Design Department Deputy Manager – SMAY

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