How to equip a chimney for a gas condensing boiler: 6 rules

1. The chimney must be resistant to acid corrosion

The chim­ney must be made of mate­ri­als with increased resis­tance to acid cor­ro­sion. It is one thing when hot com­bus­tion prod­ucts pass through the pipe, and quite anoth­er when con­den­sate forms in it, a con­cen­trat­ed acid with a pH of 3 to 5.

2. The chimney must provide free discharge of condensate into a special reservoir

This tank (boil­er) must be equipped with a siphon water seal filled with water to pre­vent flue gas­es from enter­ing the drain pipe.

5. A constant supply of air is needed

For nor­mal oper­a­tion of the con­dens­ing boil­er, it is nec­es­sary to orga­nize a con­stant flow of air to it. This can be done in sev­er­al ways, for exam­ple, by tak­ing air from the room if there is a suf­fi­cient sup­ply of it. If there is not enough sup­ply air, the air flow is orga­nized through the same chim­ney, which is usu­al­ly made in the form of a con­cen­tric pipeline for this (coax­i­al chim­ney). Out­door air enters through the inner pipe, and flue gas­es are removed through the out­er pipe.

6. It is necessary to correctly determine the length of the chimney

The length of the chim­ney can­not be arbi­trar­i­ly large, it is deter­mined by the fan pow­er of a par­tic­u­lar boil­er mod­el. For each mod­el of the con­dens­ing boil­er, it has its own, and is indi­cat­ed in the tech­ni­cal char­ac­ter­is­tics of the prod­uct. For exam­ple, the De Diet­rich VIVADENS MCR‑P 24 mod­el is rec­om­mend­ed to be con­nect­ed to a coax­i­al chim­ney with a hor­i­zon­tal end­ing and with an air duct diam­e­ter of 60 mm and for flue gas­es of 100 m. And the length of this chim­ney should not exceed 6 m if it has a hor­i­zon­tal end­ing (out­let a pipe seg­ment exits hor­i­zon­tal­ly through the wall of the house) or 20 m if the coax­i­al chim­ney has a strict­ly ver­ti­cal design.

The edi­tors would like to thank De Diet­rich for their help in prepar­ing the mate­r­i­al.

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