Σ
²
n
= total rated output in kW
Combustion air apertures and ducts must not be closed or blocked if
installed safety equipment cannot adequately ensure that the com-
bustion equipment can only be operated when the aperture is open.
The required cross-section must not be blocked by any closure or
grille.
Emergency stop switch
The burner, the fuel supply equipment and the burner control units
must be able to be switched OFF at any time by an emergency stop
switch installed outside the installation room.
Provide a sign adjacent to the emergency stop switch with the inscrip-
tion "EMERGENCY STOP SWITCH - COMBUSTION".
Safety precautions
For gas combustion equipment, fuel lines must be equipped with the
following safety equipment immediately upstream of the gas combus-
tion equipment:
■ The fuel supply must automatically shut off in case of an external
thermal load in excess of 100 ºC.
■ Up to a temperature of 650 ºC and over a period of at least 30 min,
not more than 30 l/h (measured as air flow rate) must be able to flow
through or out of the fuel line.
Combustion equipment must be installed far enough away from com-
bustible materials and built-in furniture or be shielded from such mate-
rial/furniture, so that at the rated output of the combustion equipment,
no temperatures exceeding 85 ºC will occur. Alternatively, maintain a
distance of at least 40 cm.
Heating on board ships
Some special conditions must be observed if boilers are used to heat
accommodation on board ships:
■ On ships, the integrated products are subjected to substantial loads.
■ Observe the special requirements specified by insurance underwrit-
ers – ship classification companies
■ In some cases, our boilers cannot be used.
For that reason, please check the relevant details with our sales con-
sultants.
Load-bearing boiler cover
From 620 kW the Vitoplex is supplied with a fitted load-bearing boiler
cover.
10.2 System design
Flow temperatures
To minimise distribution losses, we recommend that you size the heat
distribution system and the DHW heating to a max. flow temperature
of 70 ºC.
For boilers supplied with a boiler control unit, limit the max. boiler water
temperature to 85 ºC. The flow temperature may be increased by
adjusting the control thermostat.
Safety temperatures
Viessmann boilers comply with EN 303 and DIN 4702, and all are CE-
designated. They are suitable for installation in sealed heating systems
to EN 12828.
■ Permissible flow temperatures (= safety temperatures):
up to 110 ºC
To EN 12953: up to 120 ºC (on request)
■ Maximum flow temperature:
approx. 15 K below the safety temperature
■ High limit safety cut-out of the boiler control unit:
Delivered condition 110 ºC
Adjustable to 100 ºC
Selection of rated output
Select boilers according to the required heat load.
The efficiency of low temperature and condensing boilers is constant
across the wide boiler load range.
Therefore, the rated output for low temperature boilers, condensing
boilers and multi-boiler systems may be higher than the calculated
heat load of the building in question.
Requirements through heat load
The requirements of EN 12831 relating to the heat load calculation are
met by the weather-compensated control units. To reduce the heat-up
load, the night setback is reduced in case of low outside temperatures.
The flow temperature will be raised for a limited time to reduce the
heat-up time after a setback period.
Design information
(cont.)
28
VIESMANN
OIL/GAS BOILERS
10
5822 426 GB
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