sy24inst2 - The Initiative Group

Rendamax
The following table lists all the flue gas data for all types.
Type
R301
R302
R303
R304
R305
R306
R307
Flue gas temperature
at full
capacity
(approx.)
Flue gas quantity at full capacity
Maximum permissible
chimney
resistance
°C m 3 /h kg/s mbar
≈ 135
≈ 135
≈ 135
≈ 135
≈ 135
≈ 135
≈ 135
130
161
214
261
345
430
513
0.033
0.040
0.053
0.065
0.086
0.106
0.127
1.8
1.8
1.0
1.0
1.0
1.0
1.0
Table 5
Flue gas data
Capacity 100%
Flow temperature 80°C
Return temperature
60°C.
5.3.5.2 Chimney
Chimney length
Because the appliance is fitted with a “premix burner” with a fan, an over-pressure is built up in
the unit. This overpressure is sufficient to overcome the resistance of the cooled burner, heat exchangers,
air intake and chimney up to a maximum of 1.8 mbar (types 1 and 2) or 1.0 mbar (types 3
to 7) external to the boiler.
The back-pressure outside the unit depends on:
a The resistance of the flue pipe
b The degree of cooling of the burner system
c The resistance of the discharge system.
The degree of cooling of the flue gasses depends on:
a the insulation value of the chimney
b the local ambient temperature
c the discharge system.
The flue connection diameters of the units have been chosen such that the speed of the flue gas
will always be approximately 5 m/s. For the appliance there will be a maximum overpressure of
approximately 1.8 mbar (types 1 and 2) or 1.0 mbar (types 3 to 7) for the flue system.
y
Owing to their high resistance, bends with an R/D ratio smaller than 1 should be avoided.
Calculation of the diameter and length
For calculating and checking the internal diameter of a flue system with mechanical discharge,
refer to the applicable national and local regulations and specifications.
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