Viessmann VIESMANN VITOLIGNO 300-H Technical Manual page 55

Design information
Prevention of combustion chamber overfilling
In accordance with TRVB 118, a fill level monitor must be installed to
prevent overfilling of the combustion chamber. The boiler has two light
barriers for firebed monitoring. A sensor directly on the insert pipe is
used to detect any indication of a burn-back risk and to counteract this
in good time by means of a short term increase in output (increase in
material feed).
Fuel supply burn-back protection (RSE)
Additional "material transport burn-back protection" depends on the
respective requirements (location, size of the fuel store, material, pres-
sure, regulations) and is a separate item from the standard delivery
ordered.
Shut-off gate valve
The shut-off gate valve is approved for use in all unpressurised fuel
stores and considered as suitable burn-back protection in accordance
with TRVB 118 (test certificate BV 2979/89).
Rotary lock valve
Due to the pressure load, at least one rotary lock valve is required to
reduce pressure between the fuel store and the boiler if wood rem-
nants are blown into fuel storage rooms by fans. The rotary lock valve
is approved for reducing pressure and is recognised by the TRVB 118
(test certificate BV 2979/89) as burn-back protection.
Low water indicator
prDIN EN 12828 specifies that boilers must be equipped with a low
water indicator.
Minimum pressure limiter
Recommended for flow temperatures in excess of 100 °C
Safety valve
Equip the boilers to EN 12828 with a type-tested safety valve. For all
other operating conditions, this must be identified in accordance with
TRD 721 with "D/G/H".
It must not be possible to shut off the connection line between the boiler
and the safety valve. No pumps, fittings or constrictions may be
present in this line.
Expansion vessel
The discharge pipe on the safety valve should be designed so as to
prevent the possibility of increases in pressure. Arrange the outlet point
of the drain line so that any water expelled by the safety valve can be
safely observed [tundish] and drained off.
7.7 Fire safety
The fire safety regulations for wood combustion systems vary from
country to country.
Fire safety in the fuel store
In principle, the measures required for this purpose are not included
in the standard delivery.
VITOLIGNO 300-H
(cont.)
As a result, the activation of any specified protection device is preven-
ted and standard mode is maintained to ensure extremely reliable heat
supply.
■ Max. permissible overpressure in the fuel store: + 500 Pa
■ Max. permissible underpressure in the fuel store: + 0 Pa
■ Up to a rated heating output of 300 kW, the low water indicator
should be provided by means of a water level limiter or a suitable
device (see prDIN EN 12828, point 4.6.2.3).
Note
The safety valve is not part of the Köb standard delivery.
Alternative in the place of the expansion vessel
An additional expansion vessel and the discharge pipe are not required
if a second high limit safety cut-out and a second maximum pressure
limiter are installed.
In principle, regulations applicable to the respective installation loca-
tion must be observed.
Note
In this regard, the conditions of the local planning office must be met
by the operator.
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