Ventilacija sa rekuperacijom toplote

Ventilation with Heat Recovery

Apr 27, 2024

Ventilacija sa rekuperacijom toplote je način održavanja kvaliteta vazduha u zatvorenim zgradama koji minimizira gubitak dragocene toplote, ali postoji nekoliko problema kojima se treba posvetiti da bi se obezbedile optimalne performanse. Opšte je poznato da sve zgrade moraju biti ventilisane u cilju obezbeđenja zdravlja i udobnosti ljudi koji u njima borave. U zgradama sa malom specifičnom potrošnjom energije, i obično, većom zaptivenošću, raste verovatnoća da mogu biti neadekvatno ventilisane, što dovodi do lošeg kvaliteta vazduha u njima. U kontekstu ventilisanja i zdravlja, trebali bismo uzeti u obzir da će se svi novi domovi u budućnosti, sa zaptivenošću ispod 10 m³/hr/m² @ 50Pa, oslanjati na određenu vrstu ventilacije. Problem je što mnogi novi domovi imaju neadekvatnu ventilaciju, često ne zadovoljavajući minimalne zahteve građevinskih propisa.

Heat recovery ventilation is a method of maintaining air quality in enclosed buildings that minimizes the loss of valuable heat. However, there are several issues that need to be addressed to ensure optimal performance. It is well known that all buildings must be ventilated to ensure the health and comfort of their occupants. In buildings with low specific energy consumption and typically higher airtightness, the likelihood of inadequate ventilation increases, leading to poor indoor air quality. In the context of ventilation and health, we should consider that all new homes in the future, with airtightness below 10 m³/hr/m² @ 50Pa, will rely on some form of ventilation. The problem is that many new homes have inadequate ventilation, often failing to meet the minimum requirements of building regulations. To ensure that heat recovery ventilation systems are fit for purpose, it is crucial to address these challenges and implement proper design, installation, and commissioning practices.

Kako energetski ciljevi dodatno povećavaju zahteve zaptivenosti - do ispod 5 m3 / hr / m2 @ 50Pa - rizik za zdravlje stanara i samu strukturu objekta raste ako zgrada ne poseduje adekvatnu ventilaciju. Standardni pristup prirodnoj ventilaciji (npr. ventilacioni otvori u ramu prozora ili rupe u zidu) možda neće adekvatno odgovarati tokom cele godine zahtevima za ventilacijom: potrebni bi bili veći ulazi i odvodi, a geometrija i volumen zgrade trebali bi pažljivo biti dizajnirati kako bi obezbedili prirodnan protok vazduha. Jednostavno povećanje količine ventilacionih otvora može biti u sukobu sa ciljem energetske efikasnosti zgrade i uticati na uslove komfora korisnika objekta.

Energy goals further increase the requirements for airtightness to below 5 m3/hr/m2 @ 50Pa - the risk to the health of the occupants and the structure of the building itself increases if the building does not have adequate ventilation. The standard approach to natural ventilation (e.g., ventilation openings in window frames or holes in the wall) may not adequately meet ventilation requirements throughout the year: larger inlets and outlets would be needed, and the geometry and volume of the building would need to be carefully designed to ensure natural airflow. Simply increasing the number of ventilation openings may conflict with the goal of building energy efficiency and affect the comfort conditions for the building's occupants.

Alternativa i sve popularnija strategija za prevazilaženje ovog problema je ventilacija sa rekuperacijom toplote, ili skraćeno MVRT (mehanička ventilacija sa rekuperacijom toplote). Sa MVRT-om, ventilatori mehanički dovode vazduh u zgradu i neprestano izvlače ustajali vazduh. Ventilatori za dovod i odvod ventiliraju jednakom brzinom što znači da je količina vazduha koji ulazi u i iz zgrade uravnotežena. Dok se dovodni sveži vazduh spolja prenosi preko izmenjivača toplote, najveći deo toplotne energije iz otpadnog vazduha se predaje dovodnom vazdušnom toku. Pritom se temperatura dovodnog vazduha značajno povećava iznad spoljne temperature, čime se smanjuje rizik od nelagode i minimizira ventilacioni gubitak toplote. Tržište MVRT-a nije ograničeno na tržište pasivnih kuća: mnoge novoizgrađene ne-pasivne kuće i kuće koje se rekonstruišu takođe koriste MVRT. Ispravno dizajnirani, instalirani i pušteni u rad MVRT sistemi trebalo bi da pružaju i održavaju dobar kvalitet vazduha u zatvorenom prostoru duži niz godina.

An alternative and increasingly popular strategy to overcome this problem is heat recovery ventilation, or HRV (Heat Recovery Ventilation). With HRV, fans mechanically supply air into the building and continuously extract stale air. The supply and exhaust fans ventilate at the same rate, meaning the amount of air entering and leaving the building is balanced. As the fresh supply air from outside passes through the heat exchanger, most of the thermal energy from the exhaust air is transferred to the supply air stream. This significantly increases the temperature of the supply air above the outdoor temperature, reducing the risk of discomfort and minimizing ventilation heat loss. The HRV market is not limited to the passive house market: many newly built non-passive houses and renovated houses also use HRV. Properly designed, installed, and commissioned HRV systems should provide and maintain good indoor air quality for many years.

Da odgovara svrsi

To be fit for purpose.

MVRT sistemi mogu pomoći u održavanju uslova komfora samo ako su usklađeni sa konceptom zaptivenosti zgrade. Potrebno je zbog toga obezbediti da što više vazduha, kroz i iz zgrade, prođe kroz izmenjivač toplote.

MVRT systems can help maintain comfort conditions only if they are aligned with the building's airtightness concept. It is necessary to ensure that as much air as possible, through and from the building, passes through the heat exchanger.

Izmenjivači toplote u MVRT sistemima

Heat Exchangers in MVRT Systems

Izmenjivači toplote u MVRT sistemima treba da povrate dovoljnu količinu toplote iz otpadnog vazduha kako bi njihove performanse zadovoljile kako zahteve komfora tako i ulaganja. Ova karakteristika izmenjivača se naziva koeficijent rekuperacije i obično se navodi za skoro sve sisteme na današnjem tržištu, a sve veći broj njih ima logotip sertifikata Instituta za pasivnu kuću. To znači da su prošli dodatne testove kako bi potvrdili da između ostalog ispunjavaju i zahtev za minimalnom efikasnošću povrata toplote od 75%. U stvari, mnogi sistemi danas navode koeficijent rekuperacije od preko 90%. Ali treba biti oprezan. Samo zato što je za jedinicu navedena ova impresivna efikasnost ne znači da će ona u stvarnosti biti postignuta. Efikasnost instaliranog sistema je funkcija efikasnosti izmenjivača toplote, zaptivenosti omotača zgrade i MVRT sistema (uključujući i kanale), te ispravnog podešavanja protoka vazduha i balansiranja prilikom puštanja u rad. Međutim, na efikasnost utiče i okruženje u kome je sistem instaliran, pa bi MVRT jedinica i svi distribucioni kanali povezani na nju (na toploj strani izmenjivača toplote) trebalo da budu ugrađeni unutar termičkog omotača zgrade.

Heat exchangers in MVRT systems should recover enough heat from exhaust air to meet both comfort and investment requirements. This characteristic of the exchanger is called the recovery coefficient and is usually stated for almost all systems on the market today, and an increasing number of them have the Passive House Institute certification logo. This means they have undergone additional tests to confirm, among other things, that they meet the requirement for a minimum heat recovery efficiency of 75%. In fact, many systems today claim a recovery coefficient of over 90%. But caution is necessary. Just because this impressive efficiency is stated for a unit does not mean it will be achieved in reality. The efficiency of the installed system is a function of the efficiency of the heat exchanger, the airtightness of the building envelope, and the MVRT system (including ducts), and proper airflow adjustment and balancing during commissioning. However, efficiency is also influenced by the environment in which the system is installed, so the MVRT unit and all distribution ducts connected to it (on the warm side of the heat exchanger) should be installed within the building's thermal envelope.

Rad tokom cele godine

Year-round Operation

Može se činiti očiglednim da je ventilacija u zgradama stalni zahtev tokom cele godine. Dakle, iako je efikasan rad ventilacionog sistema važan, još je od veće važnosti da on bude sposoban da radi tokom cele godine. Mnogi sistemi sadrže mogućnost za „by pass“ u letnjem periodu, tako da se toplota odbacuje, a ne dolazi do njene rekuperacije u toplijim periodima. Neki jeftiniji sistemi jednostavno isključuju ventilator za ubacivanje vazduha, menjajući sistem u sistem samo za ekstrakciju. To znači da će možda biti potrebno otvaranje prozora kako bi se omogućio ulaz vazduha u zgradu tokom leta. Zimi, kada će prozori najverovatnije biti zatvoreni, mora se osigurati nesmetan rad sistema. Ipak, mnogi MVRT sistemi na tržištu nisu u stanju da rade tokom cele godine, i automatski će se isključiti radi zaštite izmenjivača toplote kada se spoljna temperatura približi tački mržnjenja. To je zato što bi kondenzacija koja se formira na izmenjivaču toplote mogla biti prekomerna tokom ovih uslova, uz dalji rizik da će se hladna strana izmenjivača zamrznuti, što može oštetiti jedinicu. Ali ovo bi se isključivanje moglo dogoditi u trenutku kada su zdravlje i udobnost ljudi u objektu najviše zavisni od dobrog protoka vazduha kroz sistem. Projektanti moraju da uzmu u obzir ova funkcionalna ograničenja: izbor jedinice na osnovu kapaciteta zapreminskog protoka jednostavno nije dovoljan. Pomoćna oprema, poput predgrejača na dolaznom vazdušnom toku je obavezna kada to nije sastavni deo MVRT jedinice.

It may seem obvious that ventilation in buildings is a constant requirement throughout the year. Therefore, while efficient operation of the ventilation system is important, it is even more crucial that it can operate year-round. Many systems include a bypass option in the summer period, so heat is discarded, and no heat recovery occurs during warmer periods. Some cheaper systems simply turn off the air supply fan, converting the system to an extraction-only system. This means windows may need to be opened to allow air into the building during the summer. In winter, when windows are likely to be closed, uninterrupted system operation must be ensured. However, many MVRT systems on the market cannot operate year-round and will automatically shut off to protect the heat exchanger when the outside temperature approaches freezing. This is because condensation forming on the heat exchanger could be excessive under these conditions, with a further risk of the cold side of the exchanger freezing, which could damage the unit. But this shutdown could occur just when the health and comfort of people in the building most depend on good airflow through the system. Designers must take these functional limitations into account: choosing a unit based on volume flow capacity alone is not enough. Auxiliary equipment, such as preheaters on the incoming airflow, is mandatory when not integrated into the MVRT unit.

Pitanja smeštaja i pristupa

Placement and Access Issues

MVRT jedinice, pomoćna oprema i sistemski kanali mogu zauzeti značajnu količinu prostora. Pored predgrejača, pasivni kućni dodaci mogu uključivati i naknadni grejač u distribuciji dovodnog vazduha za primarno grejanje objekta. Neophodno je da projektanti objekata planiraju smeštaj ove opreme na takav način koji će podstaći dugoročan, uspešan rad sistema, što uključuje jednostavnost pristupa za održavanje. Ako je od samog početka donesena odluka da se jedinica instalira u potkrovlje (posebno hladno), ovu odluku je potrebno ponovo razmotriti. Većina kvarova na MVRT sistemu odnosi se na loš pristup, jer nezgodne lokacije znače da ih je teško pravilno instalirati i puštati u rad. A ako je pristup mestima za redovnim izmenama filtera previše težak, oni se takođe verovatno neće menjati.

MVRT units, auxiliary equipment, and duct systems can occupy a significant amount of space. In addition to preheaters, passive house accessories may include a supplementary heater in the supply air distribution for primary heating of the building. It is essential for building designers to plan the placement of this equipment in a way that will promote long-term, successful system operation, which includes ease of access for maintenance. If the initial decision was to install the unit in the attic (especially a cold one), this decision needs to be reconsidered. Most failures in MVRT systems are related to poor access, as inconvenient locations make proper installation and commissioning difficult. And if access to areas for regular filter changes is too challenging, they are also likely not to be changed.

Filteri

Filters

Održavanje filtera je česta tema kod MVRT sistema. Primarna funkcija filtera je zaštita sistema i izmenjivača toplote od prašine i čestica koje ga začepljuju. Kao sekundarna funkcija, ova filtracija može biti od koristi za ljude u objektu, smanjujući broj čestica u unutrašnjem vazduhu koje ulaze spolja. Postoji sve više dokaza koji ukazuju na to da su stanari koji žive u domovima sa ventilacijom sa MVRT doživeli respiratorna poboljšanja. Iako će veliki deo ovih zdravstvenih poboljšanja verovatno biti posledica povećanja broja izmena vazduha, prisustvo filtera (i povećana zaptivenost zgrade) verovatno imaju ulogu, mada su potrebna dodatna istraživanja da bi se to potvrdilo. Dostupne su različite vrste filtera: opšti i fini. Fini filteri, npr. Tip F7 za sitne čestice, treba koristiti (kao što je potrebno za pasivne kuće) ako je poželjan veći stepen filtracije. Opšti filtri, npr. G4 za grube čestice, obično su dovoljne za zaštitu sistema. Treba imati na umu da, što je finiji filter, to je veći otpor na sistemu i potrebno je redovnije održavanje. Ako održavanje filtera nije rutinsko, performanse sistema će uskoro biti ugrožene. U zavisnosti od lokacije, izmena filtera se mora planirati najmanje dva puta godišnje, ili svaki kvartal. Ako se ovaj nivo održavanja ne može uzeti u obzir, tada MVRT možda nije odgovarajuća strategija za vaš projekat. Takođe je bitno istaći da troškovi zamene filtera godišnje mogu biti veći od troškova sistema za električnu energiju. Završna napomena o filterima: većina instalacija koriste ventilacione rešetke za odvod vazduha u vlažnim prostorijama u kući, uključujući kuhinju. Međutim, ako želimo zaštititi kanale i izmenjivač toplote filterima u rekuperatoru, zašto ne bismo taj princip proširili i na kuhinju? Masnoća od kuvanja može ući u kanal i olakšati prianjanje prašine i drugih nečistoća i ugroziti performanse sistema. Uvek je najbolje koristiti filtrirani terminal za ekstrakciju u kuhinji, koji obično koristi jednostavan (jeftini) filtar od filca kako bi sprečio masnoću iz kuhinje da uđe u sistem za ventilaciju.

Filter maintenance is a common topic with MVRT systems. The primary function of filters is to protect the system and heat exchanger from dust and particles that clog it. As a secondary function, this filtration can benefit people in the building by reducing the number of particles in the indoor air that come from outside. There is increasing evidence that residents living in homes with MVRT ventilation have experienced respiratory improvements. Although much of these health improvements are likely due to the increased number of air changes, the presence of filters (and increased building airtightness) likely play a role, though further research is needed to confirm this. Various types of filters are available: general and fine. Fine filters, e.g., Type F7 for fine particles, should be used (as required for passive houses) if a higher degree of filtration is desired. General filters, e.g., G4 for coarse particles, are usually sufficient to protect the system. It should be noted that the finer the filter, the greater the resistance to the system and the more regular maintenance required. If filter maintenance is not routine, system performance will soon be compromised. Depending on the location, filter changes must be planned at least twice a year, or quarterly. If this level of maintenance cannot be considered, then MVRT may not be a suitable strategy for your project. It is also important to note that the cost of replacing filters annually can be higher than the cost of the system's electricity. A final note on filters: most installations use ventilation grilles for air extraction in wet rooms in the house, including the kitchen. However, if we want to protect the ducts and heat exchanger with filters in the recuperator, why not extend that principle to the kitchen? Cooking grease can enter the duct and facilitate the adhesion of dust and other contaminants, compromising system performance. It is always best to use a filtered terminal for extraction in the kitchen, which typically uses a simple (cheap) felt filter to prevent kitchen grease from entering the ventilation system.

Distribucija vazduha

Air Distribution

MVRT sistemi obično distribuiraju vazduh do i iz prostorija zgrade mrežom kanala koji završavaju u rešetkama ili ventilima montiranim na tavanicu ili zid. Ovaj sistem kanala, plus terminali i filteri, dodaće određenu količinu pritiska pri bilo kom datom protoku. Za to postoji nekoliko termina, uključujući: ukupni pritisak; sistemski pritisak; spoljni pritisak; statički pritisak kao i otpor sistema. Što je veći pritisak sistema, potrebna je veća snaga ventilatora za zadati protok vazduha. U bilo kojem ventilacionom sistemu, ali posebno za MVRT (koji ima najveću dužinu kanala u sistemu u poređenju s drugim tipovima), neophodno je da se izračunava pritisak u sistemu prilikom projektovanja kanala kako za pravac spoljašnji vazduh/dovodni vazduh tako i za pravac odvodni vazduh / otpadni vazduha. U suprotnom nećete moći da odaberete MVRT jedinicu odgovarajućeg kapaciteta za isporuku protoka vazduha koji vam je potreban. Ventilacioni kanali su obično najslabija karika u bilo kojem sistemu ventilacije i često su glavni uzrok loših performansi. Ima mnogo oblika, ali odabir pravog dizajna, veličine i tipa biće od presudnog značaja za pravilan rad sistema.

MVRT systems usually distribute air to and from the rooms of the building through a network of ducts that terminate in grilles or vents mounted on the ceiling or wall. This duct system, plus terminals and filters, will add a certain amount of pressure at any given flow rate. There are several terms for this, including: total pressure; system pressure; external pressure; static pressure, and system resistance. The higher the system pressure, the greater the fan power needed for a given airflow. In any ventilation system, but especially for MVRT (which has the longest duct length in the system compared to other types), it is necessary to calculate the system pressure when designing ducts for both the outdoor air/supply air direction and the exhaust air/waste air direction. Otherwise, you will not be able to select an MVRT unit of the appropriate capacity to deliver the airflow you need. Ventilation ducts are usually the weakest link in any ventilation system and are often the main cause of poor performance. There are many shapes, but choosing the right design, size, and type will be crucial for the system's proper operation.

Vrste ventilacionih kanala

Types of Ventilation Ducts

Kanali se isporučuju u više oblika i izrade: čelični, aluminijumski, plastični; kruti, polu-kruti i fleksibilni; okrugli, pravougaoni, ovalni itd. Širok spektar izbora može biti zbunjujući. Ako je moguće, izbegavajte pravougaone kanale, posebno za dovod vazduha gde je kanal pod pozitivnim pritiskom: karakteristike protoka vazduha pod ovim uslovima su mnogo bolje sa kružnim ili ovalnim kanalima. Izbor materijala se uglavnom svodi na budžet projekta. Čvrsti čelični kanali su najsnažniji, a samim tim i lakši za čišćenje. Trebalo bi da traju dugo (30+ godina), ali će ta dodatna korist povećati početno kapitalno ulaganje. Bez obzira da li su metalni ili plastični, uvek koristite zaštitne konektore, zavoje, T račve, itd. Proverite da li svi priključci imaju hermetičko zatvaranje i da li su mehanički povezani. I uvek koristite kanale gde su dostupni podaci o performansama protoka vazduha: izbegavajte "naručene" kanale. Postoje dva glavna tipa konfiguracije kanala za distribuciju vazduha do i od svake prostorije: granski i radijalni sistem. Sa sistemom grana, glavne grane se smanjuju kako se svaka prostorija napaja iz glavne grane. Radijalni sistemi su sve češći, gde se glavni dovodni i odvodni kanali iz MVRT jedinice završavaju u plenum kutijama iz kojih je svaka prostorija napojena. Postoje prednosti i mane kod svakog tipa, mada neki dobavljači MVRT-a počinju široko promovisati radijalni sistem. Međutim, treba razmotriti nekoliko stvari pre nego što se odlučite za najprikladnije rešenje - svaki pristup možda neće odgovarati svakoj instalaciji. Takođe, sa hibridnim pristupom nema ništa loše: sve je moguće pod uslovom da je pravilno dizajniran i da se može smestiti u objekat. Neke ključne tačke koje treba uzeti u obzir za svaku vrstu konfiguracije.

Ducts come in various shapes and constructions: steel, aluminum, plastic; rigid, semi-rigid, and flexible; round, rectangular, oval, etc. The wide range of choices can be confusing. If possible, avoid rectangular ducts, especially for air supply where the duct is under positive pressure: airflow characteristics are much better with round or oval ducts under these conditions. The choice of material mainly depends on the project's budget. Solid steel ducts are the strongest, and therefore easier to clean. They should last a long time (30+ years), but that added benefit will increase the initial capital investment. Whether metal or plastic, always use protective connectors, bends, T-junctions, etc. Ensure all connections have airtight sealing and are mechanically connected. And always use ducts where airflow performance data is available: avoid "custom-made" ducts. There are two main types of duct configurations for distributing air to and from each room: branch and radial systems. With a branch system, the main branches taper as each room is fed from the main branch. Radial systems are becoming more common, where the main supply and exhaust ducts from the MVRT unit terminate in plenum boxes from which each room is fed. There are advantages and disadvantages to each type, although some MVRT suppliers are starting to widely promote the radial system. However, several things should be considered before deciding on the most suitable solution - each approach may not fit every installation. Also, there is nothing wrong with a hybrid approach: anything is possible as long as it is properly designed and can be accommodated in the building. Some key points to consider for each type of configuration.

Za granski:

For Branch:

Ovaj pristup ima niže turbulentne karakteristike, jer su grane napravljene da omoguće glatki protok vazduha, u poređenju sa plenum sistemima;
Ovi sistemi zahtevaju veće količine kanala većeg prečnika, minimalno 100 mm, sa glavnom granom do oko 160 mm, što može prouzrokovati probleme sa smeštajem, posebno kada se provlači kroz spušten plafon;
Balansiranje protoka vazduha u prostorijama prilagođavanjem rešetki ventila u sobi oslanja se na dobar dizajn kanala kako bi se osiguralo da lokalna brzina (dakle buka) nije previsoka za potrebnu količinu protoka vazduha;
Možda je potrebno dodatno prigušivanje zvuka, posebno za metalne kanale;
U ovom sistemu, verovatno će biti više priključaka, zavoja i cevnih kanala (u poređenju sa polu-čvrstim, radijalnim) i većeg rizika od curenja vazduha, zavisno od kvaliteta kanala.

This approach has lower turbulence characteristics, as the branches are made to allow smooth airflow, compared to plenum systems;
These systems require larger quantities of larger diameter ducts, at least 100 mm, with the main branch up to about 160 mm, which can cause space issues, especially when passing through a dropped ceiling;
Balancing the airflow in the rooms by adjusting the grille valves relies on good duct design to ensure that local speed (and thus noise) is not too high for the required airflow amount;
Additional sound attenuation may be required, especially for metal ducts;
In this system, there are likely to be more connections, bends, and duct pieces (compared to semi-rigid, radial) and a higher risk of air leaks, depending on duct quality.

Za radijalni:

For Radial:

Ovi sistemi se mogu jednostavnije ugraditi, jer radijalni kanali između plenuma i prostorije omogućavaju manji prečnik (obično 75 mm), i više dozvoljavaju korišćenje polukrutog kanala. Međutim, prostorije sa većim protokom (npr. kuhinje i velike prostorije) mogu zahtevati dva radijalna kanala do svake rešetke;
Potrebno je manje prigušivanje zvuka;
Potencijalni nedostatak je da trebate pronaći dodatni prostor za ulaze i izlaze iz plenum kutija. Oni bi trebali biti postavljeni centralno u objektu (ne potkrovlju, osim ako nije u pitanju prizemni objekat) da bi se smanjile radijalne dužine;
Koristite kvalitetne kutije za plenum, jer loše mogu prouzrokovati značajno curenje vazduha;
Puštanje radijalnih sistema u rad može biti komplikovano jer je za svaki radijalni kanal potrebno podešavanje preko isporučenih regulatora protoka ili amortizera i može potrajati neko vreme da bi se pravilno podesili.

These systems can be simpler to install, as radial ducts between the plenum and room allow for a smaller diameter (usually 75 mm), and more permit the use of semi-rigid duct. However, rooms with higher flow rates (e.g., kitchens and large rooms) may require two radial ducts to each grille;
Less sound attenuation is required;
A potential drawback is the need to find additional space for the inlets and outlets of the plenum boxes. They should be centrally located in the building (not in the attic, unless it's a single-story building) to minimize radial lengths;
Use quality plenum boxes, as poor ones can cause significant air leakage;
Commissioning radial systems can be complicated as each radial duct requires adjustment via supplied flow regulators or dampers and may take some time to properly set up.

Izolacija

Insulation

Izolacija kanala je važna gde je to neophodno – kako bi se minimizirali gubici toplote kroz sistem i smanjio rizik od kondenzacije. Pod pretpostavkom da je MVRT jedinica ugrađena unutar termičkog omotača, tada će biti potrebno izolovati dovodne i odvodne kanale na hladnoj strani izmenjivača toplote. Nastanak kondenzacije na tim kanalima biće na spoljnoj strani kanala, tako da izolacija mora biti otporna na paru. Kanali za distribuciju na toploj strani izmenjivača toplote ne zahtevaju izolaciju, osim ako: a) prolaze kroz negrejani prostor (npr. Hladno potkrovlje), u tom slučaju moraju se u potpunosti izolovati da spreče pojavu kondenzacije, koja će se dogoditi na unutrašnjoj strani kanala (izolacija ne mora biti otporna na paru, iako je to i dalje dobra praksa) ili: b) distribucija dovodnog vazduha uključuje naknadno dogrevanje (npr. neke pasivne kuće) gde bi bila potrebna izolacija otporna na paru.

Insulation of ducts is important where necessary – to minimize heat losses through the system and reduce the risk of condensation. Assuming the MVRT unit is installed within the thermal envelope, it will be necessary to insulate the supply and exhaust ducts on the cold side of the heat exchanger. Condensation forming on these ducts will be on the outside of the ducts, so the insulation must be vapor-resistant. Distribution ducts on the warm side of the heat exchanger do not require insulation, unless: a) they pass through unheated space (e.g., a cold attic), in which case they must be fully insulated to prevent condensation, which will occur on the inside of the duct (the insulation does not need to be vapor-resistant, though it is still good practice) or: b) the supply air distribution includes supplementary heating (e.g., some passive houses) where vapor-resistant insulation would be required.

Da biste osigurali dobru distribuciju vazduha u svakoj sobi, važno je i odabrati i pravilno locirati ventile/rešetke za raspodelu vazduha. Uvek je važno proveriti karakteristike distribucije vazduha prilikom specifikacije proizvoda za distribuciju vazduha. Ali kao opšti princip, ventili za difuziju vazduha koji se montiraju na plafon najbolje su postavljeni centralno u prostoriji, jer to omogućava najveću fleksibilnost kod distribucije vazduha. Ventile za izbacivanje vazduha u mokrim prostorijama idealno bi trebalo da budu postavljene na plafon, ali ako treba da budu montirani na zid, trebalo bi da ciljate postavljanje ventila na 400 mm od plafona kako biste maksimizirali efikasnost uklanjanja vlage. MVRT sistemi se najčešće oslanjaju na „efekat kaskade“. Ovde se vazduh kreće kroz objekat, od tačaka snabdevanja do tačaka izbacivanja, čime se izbegava potreba, obično, za dovodnim vazdušnim tačkama u hodnicima, kupatilima itd. Da bi se ovo izvelo, prenos vazduha između svih ventilisanih prostorija je od presudne važnosti, a to se obično postiže pravljenjem prostora od 10 mm ispod unutrašnjih vrata, mada se tačna dimenzija može izračunati prema dizajniranim količinama protoka vazduha.

To ensure good air distribution in each room, it is also important to choose and properly locate air distribution valves/grilles. It is always important to check the air distribution characteristics when specifying air distribution products. But as a general principle, air diffusion valves mounted on the ceiling are best placed centrally in the room, as this allows the greatest flexibility in air distribution. Extraction valves in wet rooms should ideally be mounted on the ceiling, but if they need to be wall-mounted, aim to place the valve 400 mm from the ceiling to maximize moisture removal efficiency. MVRT systems most often rely on the “cascade effect”. Here, air moves through the building, from supply points to extraction points, thus avoiding the need, typically, for supply air points in corridors, bathrooms, etc. To achieve this, air transfer between all ventilated rooms is crucial, and this is usually achieved by creating a 10 mm gap under the internal doors, although the exact dimension can be calculated according to the designed airflow quantities.

Kapacitet sistema

System Capacity

Tabela prikazuje primer karakteristika performansi ventilatora ili krivih ventilatora za tipičnu MVRT jedinicu. Neophodno je da se grafikon specifičan za jedinicu koja je predložena za projekat pomno ispita, kako bi se osiguralo da ona bude odgovarajuća u cilju ispunjavanja projektovanih protoka. Teoretski, jedinica u ovom primeru ima kapacitet oko 350 kubnih metara na sat (m³/h) pri pritisku sistema 0 Pa (tj. Nultog otpora - izolovan od sistema kanala), dok radi na 100% maksimalne brzine. Međutim, zavisno od dizajna kanala, pritisak u sistemu može biti od 50 do 150 Pa pri normalnom režimu rada. Pretpostavljajući da je pritisak 100 Pa i normalni radni protok od 200 m³/h, grafikon pokazuje da će sistem raditi sa oko 75% svog kapaciteta. Veće podešavanje na protok od 300 m³/h moglo bi povećati pritisak sistema na oko 200 Pa, ali sada ventilatori rade sa oko 95% kapaciteta. Ova jedinica zadovoljava potrebe za kapacitetima. Ali ovaj kapacitet zasnovan je na ispunjavanju minimalnih zahteva za projektovanje (tj. u skladu sa građevinskim propisima). U stvarnosti, ovaj kapacitet može potceniti stvarne potrebe zgrade. Na primer, koliki će uticaj imati broj stanara, njihova gustina, aktivnost i stvaranje vlage na potrebe ventilacije? Poenta ovde nije nikad ciljanje dizajna samo da bi se zadovoljio minimalni protok vazduha, jer možda nećete imati dodatni kapacitet ukoliko za to bude potrebe.

The table shows an example of fan performance characteristics or fan curves for a typical MVRT unit. It is essential to closely examine the graph specific to the unit proposed for the project to ensure it is suitable for meeting the designed flow rates. Theoretically, the unit in this example has a capacity of about 350 cubic meters per hour (m³/h) at 0 Pa system pressure (i.e., zero resistance - isolated from the duct system), operating at 100% maximum speed. However, depending on duct design, system pressure can range from 50 to 150 Pa in normal operating mode. Assuming a pressure of 100 Pa and a normal operating flow of 200 m³/h, the graph shows the system will operate at about 75% of its capacity. Higher settings at a flow of 300 m³/h could increase the system pressure to around 200 Pa, but now the fans are operating at about 95% capacity. This unit meets capacity needs. But this capacity is based on meeting minimum design requirements (i.e., according to building regulations). In reality, this capacity may underestimate the actual needs of the building. For example, what impact will the number of occupants, their density, activity, and moisture generation have on ventilation needs? The point here is never to design just to meet the minimum airflow, as you may not have additional capacity if needed.

Performanse sistema

System Performance

Takođe je važno da shvatite da što je bliže maksimalnoj krivoj, više električne energije će sistemu trebati da zadovolji projektovane performanse. Dobra praksa bi bila da odaberete jedinicu koja ima veći kapacitet, gde se normalna projektovana brzina protoka može postići sa ne više od 60% raspoloživog kapaciteta, i visoka sa ne više od 80% kapaciteta. Prilikom određivanja veličine i izbora jedinice takođe je važno uzeti u obzir kontrolu ventilatora. Mnoge jedinice sa nižim i srednjim cenama jednostavno pokreću ventilatore promenljive brzine na podešavanju odabranom tokom puštanja u rad. Međutim, neće trebati dugo da se ležajevi motora istroše, a filteri da se sve više zaprljaju, što će postepeno smanjivati protok vazduha. Najbolje je specificirati sisteme koji imaju konstantnu regulaciju zapreminskog protoka vazduha, tako da ventilatori automatski regulišu svoju brzinu kako bi održali zadati protok vazduha i u slučaju kada se pritisak sistema poveća. Ako specificirate sistem bez ovog stepena kontrole, od početka ćete morati da osigurate veći kapacitet. Sistem bi morao da se pusti u rad sa protokom većim od projektovanih vrednosti zbog budućeg potencijalnog smanjenja performansi.

It is also important to understand that the closer it is to the maximum curve, the more electrical energy the system will need to meet the designed performance. Good practice would be to select a unit with a larger capacity, where the normal designed airflow rate can be achieved with no more than 60% of available capacity, and high with no more than 80% capacity. When sizing and selecting the unit, it is also important to consider fan control. Many lower and mid-priced units simply run variable speed fans at the setting chosen during commissioning. However, it will not take long for motor bearings to wear out and filters to become increasingly dirty, gradually reducing airflow. It is best to specify systems with constant air volume regulation, so that the fans automatically adjust their speed to maintain the set airflow even as system pressure increases. If you specify a system without this level of control, you will need to ensure greater capacity from the start. The system would need to be commissioned with flows higher than the designed values due to potential future performance reduction.

Buka ventilacionog sistema

Ventilation System Noise

Faktor buke može biti vrlo značajan i često se zanemaruje tokom faza projektovanja i ugradnje. Buka je razlog broj jedan zbog kojeg nezadovoljni stanari isključuju mnoge loše ventilacione sisteme! Dobra projektantska praksa bila bi locirati MVRT jedinice dalje od područja spavanja: još jedan razlog da se jedinice ne postave u potkrovlje. Šum se može umanjiti dimenzioniranjem većeg sistema koji radi na nižim brzinama, smanjujući na taj način buku motora. Ali buka koja se odnosi na MVRT sisteme nije samo zbog mehaničke buke ventilatora. “Zviždanje” zbog lokalne brzine vazduha značajan je razlog za pritužbe na buku, a to se može povezati ili sa: lošim dizajnom kanala (manjih dimenzija od potrebnih); loša instalacija (npr. oštre ivice i zavoji); ili loše puštanje u rad (npr. pogrešno podešavanje ventila/rešetki u sobama). Dobar dizajn kanala obično uključuje slabljenje zvuka radi smanjenja buke u sistemu, a ako sistem ogranaka prolazi kroz kanale između prostorija - posebno za metalne kanalizacije - možda će vam trebati prigušivači za poboljšanje privatnosti. Vibracija iz MVRT jedinica može predstavljati dodatnu smetnju i može se javiti ako je jedinica slabo montirana ili ako je kanal slabo instaliran. Kad god je to moguće, instalirajte jedinicu na čvrsti zid ili pod i koristite nosače protiv vibracija (koji se često isporučuju kao dodatna oprema).

Noise factor can be very significant and often overlooked during design and installation phases. Noise is the number one reason dissatisfied occupants turn off many poor ventilation systems! Good design practice would be to locate MVRT units away from sleeping areas: another reason not to place units in the attic. Noise can be reduced by sizing a larger system that operates at lower speeds, thus reducing motor noise. But noise related to MVRT systems is not only due to mechanical fan noise. "Whistling" due to local airspeed is a significant reason for noise complaints, and this can be associated with either: poor duct design (smaller dimensions than necessary); poor installation (e.g., sharp edges and bends); or poor commissioning (e.g., incorrect valve/grille adjustment in rooms). Good duct design usually includes sound attenuation to reduce system noise, and if the branch system runs through ducts between rooms - especially for metal ducts - you may need mufflers to improve privacy. Vibration from MVRT units can be an additional nuisance and can occur if the unit is poorly mounted or if the duct is poorly installed. Whenever possible, install the unit on a solid wall or floor and use anti-vibration mounts (often supplied as accessories).

Puštanje u rad i korišćenje sistema

System Commissioning and Use

Cilj puštanja u rad je osigurati da je sistem pravilno podešen kako bi se osigurao projektovani protok vazduha što efikasnije i da bi se tokovi vazduha za spoljašnji/dovodni vazduh izbalansirali sa strujama odvodnog/otpadnog vazduha. Postizanje savršenog balansa u stvarnosti nije lako postići, i sve dok je disbalans manji od 10% (obavezno za pasivne kuće) onda će to biti prihvatljivo. Puštanje u rad bilo kog sistema zahteva dobro poznavanje dizajna i ugradnje tako da budu poznata ograničenja koja mogu uticati na postupak puštanja u rad. To skoro uvek znači podešavanje brzina ventilatora za dovod i odvod vazduha kako bi se uzeli u obzir različiti pritisci u sistemu sa svake strane. Često će ventilator za ubacivanje morati da radi jače od onog za izbacivanje, jer ima više kanala i otvora na dovodnoj strani (veći pritisak) u poređenju sa izbacivanjem koji ima samo vlažne prostorije. Protok vazduha - kroz sistem i u svakoj prostoriji - treba meriti pomoću kalibriranog merača zapreminskog protoka vazduha, pa je puštanje u rad obično posao stručnjaka. MVRT sistemi dolaze sa nekim oblikom ručne, automatske ili regulacije po zahtevu. U mnogim slučajevima, korisnici objekta obično nisu često u interakciji sa svojim sistemom, a potražiće regulator samo ako imaju problema - obično buke, nelagode zbog brzine vazduha ili ako primete visoke troškove rada. Automatska kontrola ventilatora, npr. na bazi vlage ne bi trebalo da dovede do naglog povećanja nivoa buke. Najbolji MVRT sistem je onaj koji ne znate da postoji: tiho i efikasno ventilira dom postižući komfor ljudi.

The goal of commissioning is to ensure that the system is properly set up to provide the designed airflow as efficiently as possible and to balance the airflows for outdoor/supply air with the exhaust/waste air streams. Achieving perfect balance in reality is not easy to achieve, and as long as the imbalance is less than 10% (mandatory for passive houses), it will be acceptable. Commissioning any system requires good knowledge of design and installation to understand the limitations that may affect the commissioning process. This almost always means adjusting the supply and exhaust fan speeds to account for the different pressures in the system on each side. Often the supply fan will need to work harder than the exhaust fan because there are more ducts and openings on the supply side (higher pressure) compared to the exhaust which only has wet rooms. Airflow - through the system and in each room - should be measured using a calibrated air volume flow meter, so commissioning is usually a job for professionals. MVRT systems come with some form of manual, automatic, or demand control. In many cases, building occupants typically do not interact with their system frequently and will seek the controller only if they have issues - usually noise, discomfort due to airspeed, or if they notice high operating costs. Automatic fan control, e.g., based on humidity, should not lead to a sudden increase in noise levels. The best MVRT system is the one you don't know exists: quietly and efficiently ventilating the home, achieving occupant comfort.