Condensing boilers in Madrid: installation, maintenance, and repair
The condensing boiler recovers the latent heat from the exhaust gases and achieves efficiencies of up to 109% over PCI. It is mandatory in new installations according to the RITE. We install and maintain the entire range in Madrid and the metropolitan area.
What makes a condensing boiler different?
In a conventional boiler, the combustion gases exit to the outside at 120–180 °C: that heat is lost. The condensing boiler adds a second heat exchanger—usually made of stainless steel or aluminum-silicon—that cools those gases below their dew point (~57 °C for natural gas). By doing so, the water vapor contained in the gases condenses and releases its latent heat (about 2,400 kJ per kg of condensed water), which is transferred to the return water of the heating circuit. This is why the efficiency expressed in LHV (Lower Heating Value) can exceed 100%: it is not magic, but rather energy that was previously discarded is being utilized.
Before replacing a boiler, compare the full cost of repair and new installation, equipment condition, material availability and your home's consumption. A percentage of savings or amortisation period cannot be promised without studying the case.
The installation requires a drain for the condensate (acidic water, pH 3–6). In most cases, it is connected directly to the sink trap or the nearest downpipe. If the municipality or the building requires condensate neutralization (large installations, office buildings), we install the limestone neutralizer in the drain line. The entire legalization process —gas installation certificate, energy certificate if applicable, communication to Industry— is handled by us.
What does our service include?
- → Installation of a new condensing boiler with a gas certificate and registration with the distributor (Naturgy / Nedgia)
- → Adaptation of the flue to a sealed twin-pipe system or installation of a stainless steel liner in a collective chimney
- → Condensate drain connection and installation of neutraliser if necessary
- → Annual RITE maintenance: combustion analysis, cleaning of the condensing heat exchanger, verification of the condensate pH, and inspection of the drainage.
- → Repair of specific condensation faults: ionisation sensor, flue extraction fan, blocked heat exchanger, clogged condensate trap
- 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.
Do you want to compare options? View all types of complete boilers
Frequently Asked Questions
Why do manufacturers say that the efficiency is 109%? Is it possible to exceed 100%?
The efficiency of 109% is expressed based on the LHV (Lower Heating Value), which is the energy of the gas measured without accounting for the latent heat of the water vapor generated during combustion. When the condensing boiler recovers that latent heat and transfers it to the water in the circuit, it extracts more useful energy than what the LHV recognizes. If, on the other hand, you measured based on the HHV (Higher Heating Value, which does include the latent heat), the efficiency would always be below 100%. The seemingly "impossible" is just a matter of reference: no thermodynamic law is being violated.
Can I install a condensing boiler with conventional radiators?
Yes. The condensing boiler works with any distribution system, including steel or aluminum radiators sized for 80/60 °C curves. What varies is the degree of utilization of the condensation: if the return water reaches more than 57 °C, the boiler does not condense and operates in conventional mode, with performance similar to that of a modern standard boiler. If you reduce the flow temperature —which can be done from the weather controller— and the radiators have sufficient surface area, the unit will condense for a longer time and efficiency will increase. It is advisable to perform a calculation of emitters before installation.
What is the condensate drain and why is it important?
The condensation process generates between 1 and 3 liters of water per hour in a domestic boiler. This water has an acidic pH (3–6) because it dissolves CO₂ and small amounts of SO₂ from the combustion gases. The boiler needs its own siphon to prevent gases from rising through the drain, and from that siphon, a pipe that leads the water to the sewage downpipe. If the drain becomes blocked or the siphon dries out (due to long shutdowns in summer), the boiler may show a fault due to internal pressure or even damage the heat exchanger. During the annual maintenance, we always check the siphon, clean the drain, and measure the pH of the condensate.