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What makes up the price of the air handling unit? Or how to select the best HRVU

The price of heat recovery ventilation unit (HRVU), like in case of every equipment, includes
– Development costs;
– Price of the components;
– Production costs;
– Manufacturer profit;
– Distributors profit.
As always, we pay the largest part of the price as manufacturer’ and distributor’ profit. The profit margin depends from a lot of factors, the biggest of these often is a trademark. In the most European countries clients believe, that units, manufactured by wester/northern EU countries, especially Germany (e.g. Wolf) or Sweden (e.g. Swegon, Systemair), are better quality, but is it so?
Real costs of the unit include development, component and production costs. The production costs generally are a matter of every manufacturer. Usually they do not consist a substantial part of the ventilation unit costs. In the East European counties, they can be lower due to lower wages, but the most Western companies have better production processes and automatization.

The biggest part of the costs (90-95%) consist of the following elements: fans, heat exchanger, automatics and casing. As a result, any manufacturer, by changing at least one internal component to cheaper one, can significantly reduce their cost. And either reduce the price or get more profit from the customer.

Fans. Many manufacturers are currently using EC-type fans due to EU efficiency requirements, so this has not been an advantage for several years already. Generally, all fans have several quality characteristics, of which their cost-effectiveness (energy consumption at the operating point) and quiet operation (i.e. the sound power level at that point) are important. Another moment: their reliability. A quality fan has a life expectancy of about 8-12 years, depending on its load.

 The best fans are manufactured by German ebmpapst or Ziehl-Abegg. The most reliable manufacturers use fans of these manufacturers in HRVU. By the way, among these companies are Lithuanian producers Komfovent and SALDA. If cheap fans from China, Eastern Europe or Poland are used, you run the risk of having to replace the fan much earlier. And can you purchase them easily… It’s another question.

Casing. Most of the component manufacturers buy externally, but the casing they must design and manufacture by themselves. The main technical characteristics of casings are:  

  • Strength (resistance to deformations);
  • Airtightness (internal and external);
  • The tightness of the filter installation;
  • Thermal resistance;
  • Sound insulation;
  • Corrosion resistance;
  • Thermal bridging factor.

Most of these features will not be found in the manufacturer’s specifications. Except for commercial aggregates that are certified by Eurovent. However, you can find some of the information in the Ecodesign data sheet (all manufacturers in EU must provide it) or on the manufacturer’s website:

  • External leakage level indicates how much air passes through the casing. It is normal that it is up to 1.5%, higher level indicates poor design or assembly quality, and potentially higher energy losses.
  • Indoor leakage level shows how much air is mixed between airflows. In other words, you can see how much air from the extracted air from your premises gets into the supplied air. Why it is important: units extract also smelling gases from the kitchen, WC and similar premises. In the case of plate heat exchanger, it is normal that internal leakage is 1.5% (in resident HRVU), in case of a rotor: 3-4% (residential HRVU). If some manufacturer declares that internal leakage from the rotor is 1-2%, be careful. Usually it is far away from real numbers. In order to protect the room from the odors, it is often a separate extraction system is installed in WC or Kitchen.
  • Sound insulation quality is indicated by Sound power level. Normally it ranges from 42 to 50 dB(A). For comparison, the refrigerator is about 40 dB(A), the dishwasher is 50 dB(A). In living premises recommended noise level is 30-35 dB (A). Please note that some manufacturers tend to display sound level at a distance of 1 or 3 m and therefore provide more attractive numbers 😊.

At the same time, I noticed that some of the producers in Central and Eastern Europe are more likely to provide more attractive numbers… They cannot be checked unless they have certified the equipment by the external organizations as e.g. Passivhaus institute or Eurovent.

Heat exchanger. The plate heat exchanger assembly consists of the heat exchanger itself with a bypass damper. For rotary heat exchanger: heat exchanger with a drive. Normally heat exchangers are made of aluminum. Part of the plate ones are made of plastic. The plastic heat exchanger has better thermal and corrosive characteristics, but it can break if it freezes. In order to return some of the moisture from the extract air in winter season, the heat exchangers can be specially coated. The enthalpy heat exchanger can return up to 60% moisture from the extract air, sorption – up to 80%. Accordingly, such a heat exchanger itself costs 2-3 times more, which affects the price of the product. Recently, cheap substitutes appeared on the market: so called “paper” heat exchangers used by cheaper manufacturers. Such a heat exchanger is not suitable for a large part of the European market and tends to deform due to moisture. The expected lifetime of such a heat exchanger is up to 2 years.

Quality heat exchangers are usually produced by companies that certify them in the Eurovent organization (https://www.eurovent-certification.com ). There are a number of manufactories that copy leading companies. However, they face the following problems: maintaining a quality level, tightness. But they’re cheaper …

It is worth mentioning the speed control device of the rotor. There are two variants of control: 0-10V and on/off. In the case of 0-10V, the rotation speed is adjusted, and there is no jerking that protects the belt and extends its life.

Automatics and electrical part. This is where most manufacturers try to save. However, these parts usually cause the most faults and there have been several cases when even market leaders have changed control components. There are usually two types of automatics: designed by the manufacturer or purchased externally (Siemens, Regin, etc.). The functionality of the control board affects not only on the control options, but also on the potential for energy savings. In the case of the simplest automatics, there are several outputs for external fan control, fire alarm and possibly to connect one CO2 or RH sensor. The cost of such an automatic is low and usually HRVU is cheaper too. To set up calendar events, you need to purchase an additional controller. The smart HRVU control system includes at least 3 temperature sensors, the ability to connect 2 external RH or CO2 sensors, connections for damper actuators and electrical heater (external or internal), filter contamination sensors, constant air flow and pressure sensors, and a series of programmed functions. This allows to optimize device performance, e.g. to save energy.

Why is it important to pay attention to internal components? Normally a 2-year warranty is provided by the manufacturer of the HRVU, in rare cases you will receive 5. The defective components can only be purchased from the manufacturer, in quite a lot of cases it is problematic, and the unit replacement is needed. A quality HRVU works for 10 years and more if it is properly maintained. One such element is the timely replacement of quality filters 😉

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