2
Product description
Logano G615 - Subject to technical modifications
8
2.2
Operating conditions
Thermostream technology is a unique feature of Buderus
cast iron boilers. Return water is preheated and mixed
within the boiler before it comes in contact with the
heating surface of the combustion chamber. The
Thermostream technology ensures there is an even
temperature distribution in the boiler and avoids
condensate forming within the combustion chamber. This
unique feature reduces thermal stress, the main cause of
failure of traditional cast iron boilers. The advantage of this
technology is the maintenance of the minimum operating
temperature of the boiler (
Æ
Tab. 3); this makes the
installation of a shunt pump unnecessary. This way, the
costs for the pump itself and its power consumption, as
well as possible failure costs are saved. The minimum
boiler operating temperature as shown in the table below
must be reached within 10 minutes and then be
maintained while the burner is running.
This operating condition can be easily achieved by the
controls monitoring the boiler temperature and reducing
the flow rate through the boiler until the required
temperature is reached. This is then maintained by
continuing to control flow based on the boiler water
temperature. The controls can reduce the flow rate by
closing the valves on the mixed heating circuits,
modulating the boiler primary pumps, closing the
motorized butterfly valves or by having a motorized valve
in the boiler return on a single boiler installation. The
Buderus 4000 series controls can manage this process
or it can be completed by the BMS.
If it is not possible for the control panel to regulate the
flow sufficiently to meet this operating condition, then a
shunt pump circuit must be fitted to avoid the type of
thermal stress that all boilers would experience in these
conditions. This shunt pump circuit can be controlled
either with a Buderus 4000 control or with a third-party
controller. Failure to ensure that the operating condition is
maintained may lead to thermal stress in the boiler and
eventual failure of the sections which would be outside
the scope of the warranty.
Control of all heating
zones with Buderus 4000
External controls (BMS) or
with Buderus 4212 with
ZM 427 or Aquastat control
Minimum flow rate
none
Minimum return temperature
°F ( °C)
none
Minimum operating temperature oil boiler
1)
1) This temperature has to be reached within ten minutes of the burner starting and has to be maintained whilst the burner is firing.
°F ( °C)
122 (50)
Minimum operating temperature gas boiler
1)
°F ( °C)
122 (50)
2)
2) 65 with partial load < 60 % °C
140 (60)
2)
Maximum supply temperature
°F ( °C)
212
3)
/248
4)
(100
3)
/120
4)
)
3) The maximum supply temperature is 212 °F (100 °C), if the boiler is operated as hot water boiler.
4) The maximum supply temperature is 248 °F (120 °C), if the boiler is operated as a hot water generator.
Maximum operating pressure
PSI (bar)
87 (6)
For operation with two-stageoil and gas bumers
–
Set the partial load stage to 60 %
Time constant of the temperature controller
sec
40
Time constant of the monitor/limiter
sec
40
Tab. 3
A heating zone with a mixing valve improves
controllability and is specifically
recommended for systems with differing
water temperature zones.
