Low NOx boilers in Madrid: regulations, installation, and maintenance
In Madrid city and its Low Emission Zone, only boilers with NOx class 5 or higher (≤ 70 mg/kWh) can be installed. We install certified low NOx boilers, handle the registration documentation, and offer annual RITE maintenance.
NOx in boilers: what they are and why they matter in Madrid
Nitrogen oxides (NOx) are byproducts of natural gas combustion at high temperatures. In dense urban environments like Madrid, they contribute to the formation of tropospheric ozone and secondary particles, which is why European and municipal regulations progressively limit them. The Ecodesign directives (ErP) and the EN 297 / EN 483 standards establish a classification from class 1 to 6: the higher the class, the lower the NOx emissions. Class 5 sets the threshold at ≤ 70 mg NOx/kWh (calculated on LHV), and class 6 at ≤ 56 mg/kWh.
In Madrid, the Air Quality Plan and the regulations of the Low Emission Zone (LEZ) Madrid Central and its extension prohibit the installation of boilers with a NOx class lower than 5. This affects any new installation or equipment replacement that requires a gas bulletin. A conventional boiler from the 90s to 2010 can emit between 100 and 200 mg NOx/kWh; replacing it with a class 5 condensing boiler reduces those emissions by between 60 and 75%. The "low NOx" label on current equipment indicates that the burner incorporates total premix technology or exhaust gas recirculation (EGR), which are the two most common techniques to reduce flame temperature and, consequently, the formation of thermal NOx.
The entire range of condensing boilers we install —Junkers Cerapur, Vaillant ecoTEC, Baxi Roca Platinum, Saunier Duval Isofast Condens, Ariston Alteas One— complies with NOx class 5 or class 6 from the factory. When installing the equipment, we process the gas installation certificate, the manufacturer's NOx class certificate, and, if required by the City Council or the distributor, the communication to the Directorate General of Industry of the Community of Madrid.
What does our service include?
- → Installation of a low NOx class 5 or class 6 boiler with complete processing of the gas certificate and registration with the distributor.
- → Provision of the technical data sheet and NOx class certificate from the manufacturer for the legalisation file
- → Communication to the Directorate General of Industry of the Community of Madrid when required
- → Annual RITE maintenance: combustion analysis with CO and NOx measurement in flue gases, adjustment of the gas-air ratio of the premix burner.
- → Repair and replacement of burner, heat exchanger, and control board in low NOx equipment of the brands we distribute
- Check applicable conditions for the equipment and contracted work: manufacturer, installation and repair do not necessarily have the same coverage. Keep the budget, invoice and documentation, without prejudice to the corresponding legal rights.
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Frequently Asked Questions
What boiler can I install in Madrid according to the emissions regulations?
In Madrid city and in the municipalities adhering to the metropolitan ZBE, it is only possible to legalize the installation of gas boilers of NOx class 5 or higher (≤ 70 mg NOx/kWh according to EN 297 / EN 483). In practice, the entire range of condensing boilers on the current market meets this requirement; recent conventional boilers (non-condensing) are also often class 5, but it is advisable to check the technical data sheet before purchasing. If you install equipment of a class lower than 5, the gas distributor may deny the supply activation.
How do I know what NOx class my current boiler is?
The NOx class is listed on the equipment's rating plate (usually inside the front cover) and in the manufacturer's technical data sheet. Look for the reference to EN 297, EN 483, or EN 15502 and the class number along with the emission value in mg/kWh. In boilers manufactured before 2010, it is common for the class not to be explicitly stated; in that case, the measured NOx value in mg/kWh is sufficient for classification: above 70 mg/kWh is class 4 or lower. If you cannot find the plate or the manual, call us and we will confirm it with the exact model.
Are low NOx and condensing boiler the same thing?
Not exactly, although in practice they almost always go hand in hand. "Low NOx" refers exclusively to the nitrogen oxide emissions level of the burner; "condensation" refers to the technology for recovering the latent heat from the gases. A boiler can be a condensation type without being low NOx (although it is rare in equipment manufactured since 2018), and theoretically, there could be a low NOx non-condensing boiler. What is common in the current market is that both characteristics coincide: the premix burners that reduce NOx are also the most compatible with the condensation process, so the modern condensation range is practically all low NOx class 5 or class 6.