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For cast-aluminum radiators, is a condensing boiler recommended?

The purchase of a condensing boiler is valid if the boiler... condenses. In order for it to condense effectively, the return temperature of the water from the circuit to the boiler must not exceed 40/45° C. This is the case for modern underfloor heating systems, or for new homes that require low energy requirements.
Cast iron radiators are often linked to older installations, which operate at higher temperatures. Most of the time, the large cast iron radiators of old installations are supplied with water at high temperatures (over 60° C). In this configuration, the boiler does not condense...
For simplicity, let's say that the efficiency of a condensing boiler will rarely be optimized with an old installation.

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