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Wall-hang condensing boilers may be classified in 2 macrocategories: boilers equipped with a single heat exchanger and boilers with two heat exchangers.
Condensing boilers equipped with a single heat exchanger usually implement a "pre-mixing" technology (the natural gas is mixed with air before entering the burner), but they experience thermal inertia related issues. The temperature reached by the burner group, and in some cases even by the heat exchanger is so high that a cool down extra time for the burner chamber by means of some fresh air ventilation system is required, in order to avoid water boiling. Obviously, such an extra function requires extra energy and lowers the so called "cyclic yield" of the boiler (the overall yield which is calculated by taking into account not only the active burning times but also the ignition and cutting off times as well).
Wall-hang condensing boilers with two heat exchangers may be equipped with the premixing system of gas with air as well or not, but they aren't affected by the above described problems, because the high temperature and the low temperature heat exchanging stages take place in two different sequential exchangers.
Obviously, natural gas condensing boilers have lower production costs, whereas natural gas wall-hang condensing boilers with two heat exchangers have higher costs.
AR.CA. Caldaie has decided to produce wall-hang type boilers implementing condensation technology only, respecting the best state-of-the-art manufacturing practices, which - among the other things - recommend the use of copper heat exchangers (copper is one of the best thermal conducting metals) for the high temperature heat exchanging stage, and a high thickness aluminum exchanger for the condensation, low temperature stage, to have a higher resistance to the condensation liquid products. Using such an arrangement, the boiler efficiency is maximized with regards to both the operating and the cyclic thermal yields. |
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