Boiler Installation in Barcelona | Aerothermal and Condensing 2026

One of the most common mistakes in boiler installation in Barcelona is oversizing. Many installers recommend 30 or 35 kW units for 80 square meter flats 'just in case'. This is a serious technical error that penalizes the performance of condensing boilers and increases gas consumption due to continuous switching on and off (short cycles).

At Fontanero Express we carry out a rigorous thermal load calculation. We evaluate the surface area, the orientation of the flat (a sunny penthouse in Sant Martí is not the same as a damp ground floor in Gràcia), the type of insulation (windows, thermal bridge break) and the number of simultaneous bathrooms. Only then can we determine the exact power in kW your home needs, ensuring the boiler modulates correctly and achieves yields above 105% on the Lower Calorific Value (LCV).

Since the ErP directive, condensing technology is the standard. Unlike old boilers that expelled flue gases at over 150ºC wasting energy, condensing ones recover the latent heat of the water vapor present in the combustion gases. By cooling these gases below the dew point (around 55ºC), the boiler extracts additional heat.

This technology requires three fundamental adaptations during installation:

• Condensate drain pipe: The boiler generates acidic water that must be channeled to a drain or PVC pipe. Never to copper or lead pipes, as it would corrode them. In complex installations, we incorporate a condensate pump with neutralizer filter.
• Special flue outlet: Requires polypropylene pipes (not metallic) with a slight slope towards the boiler so condensate returns to the unit.
• Weather compensation: To maximize savings, we install outdoor sensors and modulating thermostats that adjust the water flow temperature according to how cold it is outside.

For clients undertaking full renovations or living in single-family homes (e.g., Sarrià-Sant Gervasi), aerothermal represents the future of climate control. It consists of an air-to-water heat pump that extracts up to 75% of its energy from the outside air, capable of generating heating in winter, cooling in summer and Domestic Hot Water (DHW) all year round.

Aerothermal installation is more complex than a gas boiler. It requires locating an outdoor unit (fan) and an indoor module (hydrokit with DHW accumulator). Technically, we assess the viability of installing it with your current radiators (high-temperature aerothermal) or, preferably, combining it with underfloor heating or fan coils at low temperature to achieve a COP (Coefficient of Performance) above 4.0. In addition, these installations are the main beneficiaries of Next Generation grants and subsidies.

As authorized installers in Catalonia, compliance with the Regulation of Thermal Installations in Buildings (RITE) is non-negotiable. The regulation requires strict safety parameters in natural gas or propane installations.

We verify that the installation area (kitchen, gallery, utility room) has adequate ventilation (upper and lower grilles according to UNE 60670). If the boiler is installed indoors, a sealed flue outlet (coaxial or dual-flow) is mandatory to ensure combustion air is taken from outside and not from inside the property. An installation outside regulations not only exposes you to sanctions and problems with supply companies, but also poses a serious risk of carbon monoxide poisoning.

Our installation service is truly comprehensive. We don't leave the old boiler on the landing or on the street. According to current environmental regulations, climate control equipment is considered WEEE (Waste Electrical and Electronic Equipment). We take care of safely disconnecting the old equipment (purging gas and water), lowering it and transporting it to an authorized Clean Point for proper recycling and decontamination. This service is included in the price of all our installations.