Gas Balanced Flue Guide - Euroheat

Calculating Flue Aspect Ratios
The stove operates correctly only with air flow induced by the flue system being within the defined parameters.
To achieve these, the vertical elements of the flue, which induce flue draught and increase the air supply to the
stove, must be balanced against the horizontal elements of the flue, which offer resistance to flue draught and
reduce the air supply to the stove.
The ratio of vertical to horizontal lengths must be calculated to ensure the correct flue draught will be induced
by the proposed flue.
The difference in height between the top of the stove and the bottom of the terminal determines the vertical
height to be used in the calculation. The flue run may necessitate the vertical elements to be separated by
several horizontal runs, this is not important, only the total height gain is needed.
The horizontal length is often more tedious to determine, but again, it is the total length which needs to be
determined, regardless of their being continuous or in stages. Any 90 degree change of direction within the
flue will offer resistance to flue draught and each change of direction will offer the same resistance to the flue
draught as a horizontal run of 1000mm. For every 45 degree change in direction the resistance is that of a
horizontal run of 500mm.
BALANCED FLUE ASPECT RATIO DYNAMICS ILLUSTRATED
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
.5m vertical = 3.5m horizontal max.
Depending on
which direction your
flue configuration
will take and the
model of the stove,
a flue reduction
plate (FRP) may
or may not be
required.
See pages 24 & 25
for details.
1m vertical = 7m horizontal max.
For 1m vertical rise a flue may have a maximum horizontal run of 7m.
For each 90 degree bend introduced the horizontal run must be reduced by 1m.
For each 45 degree bend introduced the horizontal run must be reduced by 500mm.
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
© EUROHEAT DISTRIBUTORS (H.B.S) LTD. 6
Technical Guide IN1105 Ed 5 May 2009