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3
Information on installation and operation
3.13 Hydraulic connection to the heating system
▶ If the system temperatures are different, use both return connectors
RK1 (bottom) and RK2 (top).
▶ Connect heating circuits with high return temperatures to connector
RK1, and heating circuits with low return temperatures to connector
RK2.
For an optimum energy yield, we recommend supplying
a flow rate of 10 of the total nominal flow rate via
connector RK1, with a return temperature below the
dew point.
Only return connector RK1 needs to be connected if only
one return connection is used.
▶ Restrict the flow rate in the boiler to a maximum temperature
difference of at least 7 K between flow and return.
Restriction of the temperature spread is not necessary if
the system is equipped with a sludge separator.
▶ Size the pump correctly.
High flow rates and oversized pumps can result in the
accumulation of sludge or deposits on the heat
exchanger surfaces.
▶ Before connecting the boiler, flush sludge and dirt out of the heating
system.
▶ Ensure that no oxygen enters the heating water during operation.
▶ We recommend to operate the boiler in sealed unvented systems
wherever possible.
If the boiler is nonetheless used in an open vented heating system,
additional measures are required to protect against corrosion and
prevent sludge entering the boiler. Please note, the safety equipment
required for boilers installed on open vented systems vary significantly
from those on pressurised heating system.
▶ Consult the manufacturer's sales or service department for further
advise.
Information on cascade circuits:
▶ Use the actual output the boilers have been commissioned to when
sizing boiler primary pumps. The actual boiler output may vary from
the maximum output of the appliance.
▶ Ensure identical temperature differences between flow and return on
all boilers fitted in a cascade.
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3.14 Setting the minimum and maximum pressure limiters
Maximum pressure limiter
The maximum pressure limiter (accessory) must be set in such a way
that the safety valve is prevented from releasing excess pressure. To
achieve this, the setting on the maximum pressure stat must be set to
0.5 bar below the discharge pressure of the safety valve. The maximum
safety pressure of the boiler's safety valve depends on the size of the
boiler ( Tab. 5, page 8).
Example:
Safety valve pressure: P
= 5 bar
SV
Setting value, maximum pressure limiter:
5 bar 0.5 bar = 4.5 bar
The setting procedure for the maximum pressure limiter
can be found in the documentation provided with the
pressure limiter.
Minimum pressure limiter
The minimum pressure limiter (not part of the standard delivery)
(accessory) must be set in such a way that no steam bubbles form in the
boiler while still operating the boiler safely.
This setting depends on the system conditions and the siting of the
boiler system. The set point is based on the boiling pressure
corresponding the the maximum high limit stat setting (fixed at 0.5bar)
and the static head to the highest point within the heating system.
Example:
Boiler system with high limit safety cut-out setting = 110 °C
Highest consumer above the boiler = 12 m
(10 m equates to approx. 1 bar) g 1.2 bar
Safety margin = 0.2 bar (fixed value)
Response pressure P
= 0.5 bar + 1.2 bar + 0.2 bar = 1.9 bar
min
The setting procedure for the minimum pressure limiter
can be found in the documentation provided with the
pressure limiter.
3.15 Pressure maintenance
▶ Size the expansion vessels correctly.
▶ Set the pre-charge pressures correctly.
If using pump-controlled pressure maintaining systems, pressure
fluctuations will occur very frequently depending on the design of the
system and the appliance settings. Even if these pressure fluctuations
appear small, if they occur very frequently they may cause considerable
damage to the boiler, as it is designed for a predominantly static
pressure load.
To protection against damage:
▶ Ensure that every heat source is equipped with an individual
expansion vessel.
▶ Set the pre-charge pressure of the expansion vessel correctly.
Logano plus SB325 – 6 720 806 328 (2013/07)
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