CONTENT:
What is a heat or energy recovery and what is it for?
Why is it so important to renew the air and recover energy?
Relationship between recovery and efficiency
What parts of sompone a heat recovery unit?
New filter regulations. Equivalences between European and American regulations
Filters pressure loss
Filtration stages
Spanish RITE: ventilate and recover is mandatory
Download here the document about what is a heat recovery unit and the products offered by Casals Ventilación to satisfy every recovery need in a tertiary building.
Download the Casals catalogue of heat recovery units for tertiary buildings
WHAT IS A HEAT RECOVERY UNIT?
An energy recovery unit is the responsable of taking advantage of the properties of air temperature that is extracted from a building, room, or premises, to be exchanged with air driven from the outside. Inside the recuperator there is an exchange cell responsible for making, as the name suggests, the exchange of indoor and outdoor air without mixing or losing energy (cold or heat).
WHY RENEW AIR AND RECOVER ENERGY
The renewal of the air inside the buildings is essential to keep the environment comfortable and healthy. It is necessary supplying clean air from the exterior and extract or renew the stale air inside to achieve an adequate air quality in any space where there are people doing some activity. Each country has specific regulations that regulate how this renovation should be done depending on the volume of the air and the number of people who are there, as well as the type of activity performed in the building or hall. The problem of air renewal in an air-conditioned building is the loss of energy. In winter, hot air is lost with the heating, and in summer, with the air conditioning, the cold is lost from the interior, which is expelled directly to the outside. On the other hand, with a recuperator not only this residual energy is not lost, but it is used. A pre-treatment (preheat or pre-cool) of the outside air is made, and thus we reduce the energy consumption of the air conditioning system since the thermal load to be fought by ventilated air will be much lower thanks to the pre-treatment of the air.
The European Union establishes ecodesign requirements (Ecodesign) for energy-related products in the Energy Efficiency Directive 2012/27 / EU by modifying the previous ErP Directive. This directive is part of the 20-20-20 target, established in the Kyoto Protocol, according to which energy consumption must be reduced by 20% by the year 2020.
Casals Energy exchanger unit that comply with the ErP regulations are endowed with the maximum efficiency required by the RITE (IDA 1, ODA 2). This entails the installation of series of filters in the impulse ePM1 70%+ePM1<80% and ePM1 70% in return, this being the most restrictive level of the RITE (Regulation of thermal installations in buildings).
ELEMENTS OF AN ENERGY RECOVERY
All the energy recovery units are composed of 7 essential elements for compliance with the European ErP 2018 eco-design regulations:
1. Fans for the drive and extraction
2. Filters
3. Exchange cell
a. Backflow (yield up to 95%).
b. Cross flows (yield up to 75%).
c. Rotary (performance up to 90%, with sensible and latent heat recovery*).
d. Cellulose (yield up to 90%).
4. Partial or total bypass (in the supply of outside air).
5. Temperature probes to regulate the opening and closing of the bypass or other additional elements installed in option in the Energy exchanger unit.
6. Differential pressure switches for filter clogging. Control (see table of controls with the respective functions).
* Latent heat: recovery of heat and cold with humidity
1. THE EXCHANGER CELL
Exchange cell, exchanger or core is the name given to the part of the recuperator responsible for recovering the heat from the extraction of air. Inside there is a web of blades with opposite openings through which the air of the extraction and of the drive circulate and in passing through these sheets the heat transfer of the warmer air (in winter, inside the building) occurs with the cooler air (in winter, outside air), without mixing.
In the Casals Energy exchanger unit you will find the following exchangers:
1. CROSS FLOW EXCHANGER: the impulse and extraction air currents cross perpendicular to each other.
2. COUNTER FLOW HEAT EXCHANGER OR CONCURRENT FLOW: the impulsion and extraction air currents circulate in parallel and countercurrent. As the surface and time of passage through the interior of the exchanger is greater, the capacity for recovery is increased.
3. ROTARY EXCHANGER: the impulsion and extraction air currents exchange heat thanks to the rotary movement of the exchanger. The flow of hot air gives its heat to the metal cells of the exchanger as it passes through them. With the rotating motion, the cold air flow takes heat from the same cells. It consists of a rotor that accumulates heat, an electric motor and a housing.
2. FILTERS
2.1. Filters classifications
As established by UNE-EN 13779, the different types of air are classified according to their origin and the function performed by people in the installation. Outside air (ODA) is understood as the air coming from outside entering the system without having been treated. And we talk about indoor air (IDA) to refer to the air treated in the building or space to be ventilated.
Depending on the use of the building or premises, the category of indoor air quality (IDA) that must be reached will be, at least, the following:
IDA 1 (high quality air): Hospitals, clinics, laboratories and nurseries.
IDA 2 (good quality air): Offices, residences (common premises of hotels and similar, residences for the elderly and students), reading rooms, teaching and assimilable classrooms and swimming pools.
IDA 3 (medium quality air): Commercial buildings, cinemas, theatres, assembly halls, hotel rooms and simmilars, restaurants, coffee shops, bars, nightclubs, gyms, sports locals (except pool) and computer rooms.
IDA 4 (low quality air)
However, the classification of the filters is made according to the ODAS (outside air quality):
• ODA 1: pure air that is only temporarily dirty (eg pollen)
• ODA 2: air with high concentrations of particles and / or polluting gases.
• ODA 3: air with very high concentrations of polluting gases (ODA 3G) and / or particles (ODA 3P).
In the case of Casals, the energy recovery units are equipped with filters to comply with the IDA 1 / ODA 2 classification:
• ISO ePM1 70% (Filter F7) eff. 80-90%.
• ISO ePM1 80% (Filter F9) eff. <95%.
FILTER EQUIVALENCE CHART ACCORDING TO STANDARDS
|
EN779
(Outdated)
|
ASHRAE 52.2 |
ISO ePM 1 |
ISO ePM 2.5 |
ISO ePM 10 |
ISO Coarse |
|
G3 |
MERV 5 |
- |
- |
- |
>80% |
|
G4 |
MERV 6-7 |
- |
- |
- |
>90% |
|
M5 |
MERV 8-9 |
- |
- |
50-65% |
- |
|
M6 |
MERV 10-12 |
- |
50-65% |
65-80% |
- |
|
F7 |
MERV 13 |
50-65% |
65-80% |
>80% |
- |
|
F8 |
MERV 14 |
65-80% |
>80% |
>90% |
- |
|
F9 |
MERV 15 |
>80% |
>95% |
>95% |
- |
LOSS OF LOAD ON FILTERS
When the air passes through a filtration unit, it needs a minimum of pressure available to be able to pass the flow through the free section of the filter. In each case, the corresponding curve of the pressure drop of the filter will be indicated, a relevant factor to be taken into account in the selection of the available flow and pressure of the recuperator.
FILTRATION STAGES
The recuperators can hold up to two stages of filtration in impulsion and one in return with the aim of obtaining an optimum interior air quality. All Casals Energy exchanger unit comply with this characteristic.
OBLIGATION TO VENTILATE AND RECOVER IN THE PANISH RITE
The filters provided in the air treatment unit will be the most demanding in the Spanish RITE IDA 1. According to the Spanish regulations (RITE), the energy exchanger can be selected according to its flow and filtration according to the following table (1.4.2.5 IDA1):
|
Outside air quality |
Indoor air quality |
|
IDA 1 |
IDA 2 |
IDA 3 |
IDA 4 |
|
ODA 1 |
F9 |
F8 |
F7 |
F5 |
|
ODA 2 |
F7+F9 |
F8 |
F7 |
F5+F6 |
|
ODA 3 |
F7+GF(*)+F9 |
F7+GF(*)+F9 |
F5+F7 |
F5+F6 |
