34
accelerating combustion by an uncontrolled air supply. Your stove’s output
also depends on the chimney draught. The draught may be affected by
factors like the cross-section of the chimney or weather conditions (strong
winds, etc.).
4.5 ROOM HEATING CAPACITY / ROOM
TEMPERATURE
The room heating capacity was previously quoted according to DIN standard
18893 (last issued August 1987) and is thus no longer relevant to modern
post-1990 homes. However, the old room heating capacity value may still be
of interest as a comparative value or for use in the case of older structures
pre-dating the 1977 thermal insulation standard.
A nominal heat output of 5.0 kW for the a1/a2/a3/a4, 8.0 kW for the a4 H
2
O,
7.0 kW for the a5 and 5.9 kW for the a7/a8 corresponds to the following
room heating capacity when operated as intermittent heating (i.e. with
breaks in operation of less than 8 hours):
Room heating capacity* of ambiente stoves when used intermittently
Heating
conditions
a1/a2/a3/a4
a4 H
2
O**
a5
a7/a8
Favourable
144 m
3
56 m
3
165 m
3
88 m
3
Less favourable
84 m
3
35 m
3
95 m
3
53 m
3
Unfavourable
56 m
3
22 m
3
65 m
3
34 m
3
*
**
Considerably bigger rooms can be heated with modern thermal insulation.
Direct room heating not including water heating
A detailed explanation of ‘favourable’, ‘less favourable’ and ‘unfavourable’
can be found in DIN standard 18893. Simply put, ‘favourable’ describes a
situation where the room has only one external wall and otherwise mainly
adjoins heated internal rooms, whereas ‘unfavourable’ refers to a room with
two external walls and adjoining unheated rooms.
The values indicated above refer to structures pre-dating the 1977 ther-
mal insulation standard. They represent a simplification which is valid for
room sizes up to 200 m³. DIN 18893 standard recommended a calcula-
tion according to DIN 4701 for rooms larger than 200 m³. Nowadays, an
estimate according to TR-OL is preferable or, in particular, the calculation
should be based on DIN 12831.
4.6 HEATING IN THE TRANSITIONAL PERIOD /
UNFAVOURABLE WEATHER CONDITIONS
In the transitional period, when the outside temperature is above approx.
15°C, or during unfavourable weather conditions (down winds, etc.), disrup-
tion to the chimney draught may occur due to sudden rises in temperature,
with the result that the flue gases are not completely extracted. In these
circumstances a smaller amount of fuel should be placed in the stove and
the air adjustment lever should be moved to the maximum position (refer
to section „4.2 Controlling the Combustion Air Supply“ on page 30,
Fig.
16
). The fuel in the stove will then burn away faster (with more flames). This
will help to stabilise the chimney draught. To avoid resistance in the firebed,
it should be carefully raked at frequent intervals to remove the ash. The air
supply can be reduced slightly (middle position) when the chimney draught
has stabilised.
