12
1.15
Cast iron sections with high performance
system with three flue passes
The three flue passes structure forces the combustion gases to
circulate in the boiler body three times before exiting the dis-
charge pipe, transmitting all the energy to the water inside the
elements. Optimised combustion chamber with complete heat
insulation gets the highest yield from the fuel.
3rd pass
2nd pass
1st pass
The combustion chamber of the boiler has a positive pressure.
The boiler operates according to the principle of three vertical
passes of the flue gases.
1.16
Boiler purging
The constant ventilation of the boiler room is important for three
reasons:
1
Air is used for the combustion process inside the boiler.
2 Air is used to prevent the formation of dirt and dust, to allow
the flue gases and the fuel to come out
3 Air is used to prevent the boiler room overheating.
Ventilation for the first two reasons is constantly required. In the
third case, ventilation is needed above all for boilers that also
operate in summer.
The maximum temperature in the boiler room should not ex-
ceed 32°C.
The boiler room should be protected against frost.
BOILER
RTT 29
BOILER
RTT 39
BOILER
RTT 49
BOILER
RTT 59
BOILER
RTT 69
BOILER
RTT 79
Combustion
gas pipe
dimensions
(mm)
130
130
150
150
150
150
Height of
combustion
gas pipe
(natural gas)
(m)
3.41
4.91
6.00
8.63
5.25
7.56
7.53
10.85
10.22
14.72
12.91
18.59
Height of
combustion
gas pipe
(liquid fuel)
(m)
7.67
18.85
13.49
33.17
11.82
29.06
16.95
41.67
23.00
56.55
29.05
71.43
If the fuel is natural gas:
Type of
boiler
(*) Cross-section of the
opening for natural ven-
tilation (cm²)
(**) Volume of air
required for forced
ventilation
(***)
Lower part
Upper
part
Lower
part
Upper
part
BOILER
RTT 29
398
199
92
62
RTT 39
BOILER
440
220
122
82
RTT 49
BOILER
482
241
153
102
RTT 59
BOILER
524
262
183
122
RTT 69
BOILER
566
283
213
142
RTT 79
BOILER
608
304
243
162
(*)
If a natural ventilation system is used.
(**)
If a purging ventilation system is used
(***)
The value on the bottom shows the cleaned air coming
in, the value at the top shows the output air.
1.17
Water circulation
For the boiler to work efficiently, the difference between the
supply temperature of the water and the water return tempera-
ture should not exceed 20°C.
Moreover, the boiler should not be on or running when the wa-
ter flow rate is lower than the values indicated in the following
table.
Type of
boiler
Output
∆
t = 10 K (*)
∆
t = 20 K (*)
kCal/h
kW
Water
flow
rate
Water
resistance
Water
flow
rate
Water
resist-
ance
m
3
/h
mbar
m
3
/h
mbar
BOILER
RTT 29
25,000
29.1
2.5
14
1.3
4
RTT 39
BOILER
33,500
39.0
3.4
21
1.7
5
RTT 49
BOILER
42,000
48.8
4.2
29
2.1
8
RTT 59
BOILER 50,500 58.7
5.1
41
2.5
12
RTT 69
BOILER 59,000 68.6
5.9
78
3.0
23
RTT 79
BOILER 67,500 78.5
6.8
114
3.4
31
(*)
∆
t = temperature difference
9
The RTT boiler has been designed only for heating systems
with forced water circulation.
