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Jun 4

The Challenges for HVAC Specialists in 2020

  • June 4, 2020

Interview for “Gradat” magazine of Ivan Armianov, MSc. І CSO & CMO  І

The Challenges for HVAC specialists in 2020


Mr. Armianov, what are the main challenges facing modern HVAC systems as a result of the requirement for compliance with the new reality? To what extent are they valid for the different types of buildings by functions – offices, commercial, industrial, hotels, residential?

Most HVAC specialists are well informed and know the necessary requirements and recommendations for the design, manufacturing and developing of HVAC systems. In the current situation and the spread of the coronavirus SARS-CoV-2 (Covid-19), many people have started speculations and free conversations on the topic of ventilation and air conditioning systems. This happened not only in Bulgaria, but throughout Europe. Non-specialists stated in the early days of the state of emergency that all ventilation systems should be shut down.

We are corresponding member of the HVAC association Eurovent and partner of the HVAC federation REHVA. As soon as the rules and guidelines for work and maintenance of these associations were published, we made translations in Bulgarian and published them in order to be available for everyone, both at our web and on their websites. We also have good communication with the German Associations for Ventilation and Air Conditioning, and they together with the German Health Institute: Robert Koch Institute, which the Bulgarian government team for healthcare during Covid 19 used as the most reliable source, prepared and published guidelines. All these highly respected bodies agreed on the following recommendations:

  • Particles of coronavirus Covid-19 can be found mainly in exhaust ventilation systems. Such particles have not been detected in fresh air systems so far. To ensure that the spread of viruses and bacteria is reduced, the amount of fresh air supplied by ventilation systems must be increased at maximum and the amount of recirculated air must be stopped or severely limited.
  •  Ventilation systems should not be switched off, and if there are no occupants, they should be used to minimum speed.
  • Energy and heat recovery systems should be inspected to ensure no mixing of the two air streams.
  • Regular maintenance and cleaning of the air filters is also recommended.
  • If the ventilation systems allow and the air exchange will not be disturbed, to change the filters to a higher filtration class. Filters above F7 (EN779) or ePM1 55% (ISO16890) are recommended
  • If equipment is currently being designed or manufactured, the fans should be positioned relative to the heat exchanger in such a way as to ensure no mixing of the two air streams.

Of course, these are general guidelines and it is appropriate for HVAC specialists to prepare recommendations for each building specifically, according to the location, purpose and occupants, as well as the specifics of the air handling and air exchange installations. This is a common practice in Western Europe and especially in clean rooms, production facilities and hospitals, where it is mandatory for an engineer with a VDI certificate to prepare program for regular maintenance of HVAC systems.

What is the place of new technologies to provide high comfort and at the same time adequate protection for the inhabitants from airborne viruses and bacteria?


There are different types of systems and equipment for purification and disinfection of indoor air. None of them have yet been tested and proven to protect from Sars-CoV-2 coronavirus (Covid-19). Devices with UV lamps, devices with hepa filters and devices with non-thermal plasma, which are available on the market by us or our colleagues, help to purify the air. The main problem, however, remains surface spread or human-to-human transmission. However, I strongly recommend the use of better technology to ensure a clean and healthy microclimate for the inhabitants and to clean the air we breathe from bacteria and viruses.

In recent months, we have often recommended the installation of non-thermal plasma devices, as their method of installation and operation is similar to devices with UV lamps, but plasma particles adhere to the core of the air, as do the dust particles, and clean surfaces reached by air. This leads to better results, as found by colleagues in laboratory tests of two identical operating rooms in Italy. One operating room had a Jonix non-thermal plasma purification system installed, and the other only had a standard operating room ventilation and filtration system. The two halls are with the same load capacity. Mtimes less viruse particles and bacteria were found in the first than in the second operating room during cleaning and evaluation test, even on surfaces inaccessible for human cleaning.

At what stage – consulting, design, construction, maintenance and service, should the appropriate measures for high safety of the occupants be provided?

Today we live in a pandemic situation. This should lead investors to choose more efficient systems with better filtration and more purification systems. Of course, a large part of the buildings have already been built and the systems in them are already designed, installed and are working. Almost all of them can be retrofitted to meet best filtration and safety practices if there is a good will and willingness to invest.

A few years ago we completed the renovation of Hotel Rila in Borovets. Each air handling unit we designed had to meet the highest requirements for energy efficiency, noise and at the same time be able to be transported in parts and assembled in the machine premises. Thus we proved that if there is a synergy between investor, designer, builder, manufacturer and installer, HVAC systems can be improved at any stage of the site, regardless of whether it is now designed, built or already in operation for more than 40 years.

What is your experience with air handling systems and high occupant safety? What should investors, architects and builders strive for?

We have performed HVAC installations in many operating rooms in hospitals, laboratories and clean rooms with extremely high requirements. Of course, we have also built installations in public buildings, hotels and office buildings. All of these buildings can be inhabited in the current situation, and ventilation systems will help provide better and cleaner air and reduce virus particles.

We produced a hygienic air handling unit for the laboratory processing coronavirus samples in Pleven at the beginning of the epidemic in Bulgaria. Within 10 days we designed, manufactured and installed the unit and the installation and the lab started working. This is not a new product or new technology, but compliance with regulations and requirements for quality microclimate and production of this type of equipment are not common in our country.

Every investor, architect and builder must focus his/hers view on quality and trust the HVAC specialists. The search for the lowest price leads to errors at every level – from design, through execution and finally in operation and maintenance.

  • When money for design are not scarce, colleagues can use enough time and resources to check each part of the installations and solve problems on paper / computer. If this happens during construction – it will simply be more expensive.
  • International specialized organizations, which perform an annual audits of product manufacturers, issue a certificate and guarantee customers quality and achieved parameters. We are audited annually and our products are tested in laboratories by Eurovent, TÜV and Dedal.
  • At the end, a contractor who does not compromise on the quality must be selected for execution in order to guarantee the best results.

Only in this way, a building could provide a quality microclimate and be a safe place for its occupant

Last year TANGRA celebrated its anniversary, what new projects have you implemented and what new products are you presenting on the market?


Yes, on August 17, 2019 TANGRA turned 30 and for us it was a significant event. Throughout this period, we have not stopped presenting new products and services, as well as searching for and implementing new objects and challenges.


At the beginning of 2020 we performed the ventilation of the tunnel of Gabrovo with 10 jet fans. Together with our partners in the Czech Republic we are working on a project for renovation of schools and mandatory ventilation in classrooms. We also completed the HVAC systems in the operating rooms of the new building of the hospital “St. Ekaterina” in Sofia.


In the past two months we have renewed the range of high-efficiency energy recovery units TANGRA EVB HiE, and also we created a new range of ventilation systems with rotary regenerative heat exchangers TANGRA EVB ROT, including a built-in direct expansion module DX-M / DX-S. In our air handling units, two-stage heat and energy recovery is widespread and we have been producing such air handling units for many years. In recent years, we are increasingly producing compact ventilation units with built-in heat pump. For this reason, in the coming months we will present the two series of compact heat recovery units with built-in two-stage energy recovery and efficiency over 90%. All units produced by TANGRA are manufactured in accordance with the requirements of Eurovent, EN13053, Regulation 1253/2014 and the ErP Directive.


In all our facilities, the company’s team strives to provide a premium product with the highest efficiency, achieving and exceeding the requirements of applicable directives and regulations. An example of this are our plate heat exchangers TANGRA REC HiE. We started their production in 2013 and they covered the requirements of the Ecodesign Directive (125/2009 / EU) and Regulation 1253/2014 – minimum efficiency from 2016 67%, and from 2018 73%. When our heat exchangers were tested in a Eurovent laboratory, the efficiency measured was between 79 and 88% (EN308). European HVAC organizations are discussing a new step for minimum efficiency from 2023 – 75%. We are ready and all our products comply with ErP 2023.




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