1.The exhaust gas temperature of condensing wall mounted gas boiler with a secondary heat exchanger is around 60°C.That of an ordinary wall mounted gas boiler is generally above 160°C.

2.At the bottom of a condensing gas boiler with a secondary heat exchanger, there is a condensing water drain. The condensing  water drains from it during operation; while there is no condensing water drain in an ordinary wall mounted gas boiler.

3.To distinguish a condensing gas boiler from others by the internal structure.
    There is one condensing heat exchanger in the flue outlet;
    There is a condensing water pipe drain and a condensing water 
    neutralization box.