
Safety Safety devices in the fuel path
quite a bit higher than the light switch, and clearly
labelled. For boiler rooms that are only accessible from
outdoors, this emergency stop switch may also be
inside the boiler room, immediately next to the access
doors.
A single-pole, lockable switch or key switch is
integrated in the boiler's safety chain. When actuated,
this only stops the supply of fuel and combustion air.
The pumps continue running to cool the boiler.
Emergency stop switch for the fuel store
We recommend fitting an additional emergency stop
switch in the access area of the fuel store. Installation
in the jamb of the access door has proven effective.
The single-pole switch is integrated in the boiler's
safety chain.
6.4 Safety devices in the fuel path
European standard EN 303-5
With EN 303-5 "Heating boilers for solid fuels... up to
500 kW" safety requirements have now been
harmonised across Europe.
•Spread of fire in the fuel supply pipe.
The one-chamber rotary valve installed as
standard equipment (RSE according to
TRVB 118 H) and the negative-pressure operation
of the boiler prevent the propagation of fire (burn-
back) in the fuel supply.
•Heat conduction - surface temperature.
The surface temperature of the stoker may not
exceed 85°C in any operating mode. This is
ensured by the one-chamber rotary valve installed
as standard. Without air, burn-back into the stoker
is impossible.
•Backflow of flammable combustion products
into the store via the fuel supply pipe.
The single-chamber rotary valve installed as
standard equipment and the negative-pressure
operation of the boiler with a speed-controlled
draught fan (DÜF according to TRVB 118 H)
prevent a backflow into the fuel supply or the fuel
store.
•Shortage of combustion air or incomplete
combustion.
A shortage of combustion air is prevented by
standard residual oxygen measurement (FÜF
according to TRVB 118 H), speed-controlled
draught fan and position feedback for the air flaps.
If there is a fault in the fan or the air flaps, a safety
shutdown takes place.
Fire compartments in larger buildings
If a secure fire compartment is required between the
boiler room and the fuel store in a larger building, then
an automatic extinguishing system (sprinkler system)
must be installed in the wall opening in addition to the
requirements of EN 303-5.
Regulations for Austria - TRVB 118 H
During the official approval process, the authorised
inspector can require compliance with TRVB 118 H
"Technical directives for preventive fire safety"
(Austrian Association of Fire Brigades and Austrian
Fire Prevention Bodies).
A temperature monitoring system and manually
activated fire extinguishing system, in particular, are
also required:
•Temperature monitoring system
This is installed in the wall opening of the conveyor
screw from the fuel store to the boiler room; see
Fig. 6-5: "Temperature monitoring system".
In Austria, a capillary thermostat is supplied
with all ETA wood chip boilers for this
purpose.
•Manually activated fire extinguishing system
This fire extinguishing system is installed above
the wall opening of the conveyor screw from the
fuel store to the boiler room for fuel stores
measuring over 50 m³ and whenever fuel is stored
in a barn (to be installed by the contractor, if
required), see Fig. 6-6: "Manually activated fire
extinguishing system".
Regulations for Germany
In Germany, previous requirements only stipulated one
burn-back protection device in the fuel path and
pressure monitoring of the combustion chamber. Now,
with EN 303-5, a much more stringent safety standard
is required, which ETA also fulfils.
Regulations for Switzerland - VKF 105-03d
In Switzerland, previously a burn-back protection
device (flap, slider or rotary valve) and a sprinkler
system on the stoker were required. Now, with EN 303-
5, a much more stringent safety standard is required,
which ETA also fulfils.
Single-chamber rotary valve as standard
equipment
The standard configuration of ETA wood chip boilers
with patented ETA one-chamber rotary valve and
induced draught technique without fan, and with
combustion chamber negative-pressure in all states of
operation satisfies all requirements of EN 303-5
regarding fire propagation and recirculation of gases,