eta HACK 20, Операция, Страница: 11 / 92

Safety Safety devices
11
overheating if the pump fails. The minimum pressure in
the cold water pipe must be 2 bar and the temperature
must not exceed 15 °C.
Fig. 3-2: Thermal emergency cooling valve
1 Cold water connection
2 Isolating valve; remove hand wheel
3 Strainer
4 Thermal emergency cooling valve
5 Visible outlet to sewer
The cold water supply must be connected to the upper
connector of the safety heat exchanger; the lower
connector serves as an outlet to the sewer. To prevent
the supply line from being shut off accidentally, remove
the levers from ball valves or the hand wheels from
valves and hang them there with a piece of wire.
The discharge must have an easily visible flow path so
malfunctions can be recognised. Direct the discharged
water to the sewer via a siphon funnel or at least with
a pipe into the ground so that nobody can be scalded
if the valve is activated.
Even for cold water coming from a domestic well with
its own pump, a thermal emergency cooling valve must
be installed on the boiler. With a generously
dimensioned air vessel, enough water for cooling will
come even if there is a power failure. If the electricity
supply is very uncertain, a dedicated air vessel for the
thermal emergency cooling valve is required.
Safety shutdown by safety temperature limiter
For additional safety against boiler overheating, a
safety temperature limiter is built into the boiler. When
a boiler temperature of 105°C (tolerance 100 to 106°C)
is reached, the power supply to the draught fan and the
fuel intake is interrupted. If the boiler temperature
decreases below 70°C again, the safety temperature
limiter can be manually released for a restart of the
boiler.
Install safety valve against overpressure
A safety valve with 3 bar opening pressure must be
installed on the boiler. Every heat producer in a heating
system must be protected by at least one safety valve
against pressure exceeding the maximum operating
pressure (see EN 12828). These valves must be
designed such as to ensure the maximum permitted
operating pressure that can arise in the heating system
or parts thereof. The safety valve must be situated in
the boiler room and be easily accessible.
Fig. 3-3: Safety valve
DANGER!
Do not install any shut-off valves, strainers or such like
between the boiler and the safety valve.
The connection size of the safety valve is determined
on the basis of the heating system's maximum heating
capacity, as shown in the table.
Install the safety valve at the highest point of the heat
producer or in the flow pipe close to the heat producer.
Only in this way can it discharge heat by blowing out
hot water and steam.
The safety valve may be installed in any position, but
the upper part of the valve must not face downward.
The flow pipe may be 1 m long maximum and must be
routed in a straight line in the nominal diameter of the
valve inlet.
Valve size
a
Nominal diameter (DN)
a. The valve size is determined by the size of the inlet
connection.
Maximum heating
capacity (kW)
15 (G ½) 50
20 (G ¾) 100
25 (G 1) 200
32 (G 1 ¼) 300
40 (G 1 ½) 600
50 (G 2) 900