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Hartley and Sugden
5. Protection of chimneys agains internal condensations
The increase of boiler efficiency, the placing of an economy flap on the burn ers (stopping the admission of air when the
burner is stop ped and hence the draft into the chimney), the oversize capacity of the chimneys in relation to the red uc tion
of the installed bo iler yields, the influence of more powerful r egulation devices on the functioning time of the burners,
these are all parameters that n ecessitate the taking of certain pre cautions with a view to maximally reducing the r is k of
condensation inside the chimney with the connection of high performance boiler to chimneys, in p articular when this
involves existing chimneys.
Precaut ions to be taken :
1. Setting burner o utput accord ing to the nominal yield of the furnace.
2. Provide a draught stabi lizer of a size according to the section of the chimney, that will:
a) d uring the periods when the burner is working, stabilize the draught, reduce the dew point temperature of the water
vapour by mixing of the combustion gases with ambient air.
b)during the period when the burner is not working, ensure the ventilation o f the chimney by ambient air (by setti ng
the stabilizer t o b e not completely closed when the burner is stopped ), which enables the r emaining condensation
to be removed).
3. Avoid the applicatio n of heightening tubes on chimneys which cause exce ssive cool ing of the combustion gases.
4. In thecase of a markedlyoversized or particularly"cool" chimney(e.g. one situatednext to an exterior wall), youare advised
to provide an internal flue duct that must be placed according to the relev ant technical prescriptions.
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