Combi boilers in Madrid: installation, maintenance, and repair
The combi boiler provides heating and domestic hot water in a single unit, without an independent storage tank. It is the most installed model in Spanish homes. We work with Junkers, Vaillant, Saunier Duval, Baxi Roca, and Ariston in Madrid and the Corredor del Henares.
How does a combi boiler work?
The mixed boiler has two internal circuits: the primary heating circuit (water that circulates through the radiators or underfloor heating) and the secondary domestic hot water circuit (consumption water that is heated on demand, without being stored). When you open a tap, a sensor or flow meter detects the minimum flow of domestic hot water —usually between 2 and 3 l/min— and activates the burner as a priority. During those seconds of startup, the heating is paused: hence, the first liters of water may arrive colder than with a storage tank, which keeps hot water ready at any time.
The usual power for a dwelling of 80–120 m² ranges between 24 and 28 kW. For larger flats or those with high simultaneous DHW demand (several showers at once), it is recommended to increase to 35 kW or consider combining with an external storage tank of 50–80 litres. Electronic ignition (without a permanent pilot) and burner modulation —which adjusts the flame according to actual demand— are standard features across the current range and help reduce gas consumption.
We install mixed condensing boilers from Junkers (Bosch), Vaillant, Saunier Duval, Baxi Roca, and Ariston. All brands include a WiFi module compatible with a smart thermostat and comply with NOx class 5 required in the Madrid LEZ. The annual RITE maintenance includes combustion analysis, cleaning of the DHW heat exchanger, verification of the differential by-pass, and pressure adjustment of the circuit.
What does our service include?
- → Installation of a new combi boiler with processing of the gas certificate and registration with the distributor
- → Replacement of old boiler: disassembly, removal, and adaptation of gas, water, and flue connections
- → Annual maintenance: combustion analysis with a calibrated analyser, cleaning of the burner and the DHW plate heat exchanger, bleeding and filling of the circuit.
- → Repair of common faults: lack of pressure, defective ignition, scaled DHW heat exchanger, NTC sensor, three-way valve
- → Brands: Junkers / Bosch, Vaillant, Saunier Duval, Baxi Roca, Ariston — original spare parts in stock
- 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.
Are you looking for another type of boiler? View all types of complete boilers
Frequently Asked Questions
What is the difference between a combi boiler and a heating-only boiler?
A heating-only boiler (or "heat-only") only heats the water in the radiator or underfloor heating circuit; for domestic hot water (DHW), you need a separate storage tank or electric water heater. The combi boiler integrates both functions into a single unit, saving space and simplifying maintenance. The drawback is that it cannot supply very high simultaneous DHW flow rates, a limitation that an external storage tank can resolve.
Why does hot water take longer with a combi boiler than with a storage tank?
With an accumulator, the water is already stored hot at 60 °C; you only need to empty the cold pipe between the water heater and the tap. With a combi boiler, the water is heated on demand: when you open the tap, the flow meter activates the burner, which takes 5–15 seconds to reach the set temperature. If the distribution pipe is long, those seconds add up. Installing a DHW recirculation valve or a heating cable in the return pipe almost completely eliminates that wait.
Can I replace my old wall-mounted boiler with a condensing combi boiler?
In most cases, yes, but there are three points to verify: first, the flue must be suitable for condensation (low outlet temperature, it can generate condensate in the pipe, so if there is a shared brick chimney, a stainless steel liner must be installed); second, the installation must have a drain for the boiler's condensate; third, if your gas installation has a manual shut-off valve on the wall, the technician will check the diameter and pressure of the supply line. With those points checked, the replacement is a one-day job.