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temperature above 95 °C), the thermostat valve installed on the boiler opens, and
supplied water from the water system cools the boiler, leaves the system through
an overflow pipe (RP) of an open expansion vessel (item 10) flowing to a cooling
well (item 11), and then to a sewage system.
Direct discharge of hot water from boiler cooling is forbidden and
unacceptable, as this may damage the sewage system.
When the temperature in the sensor environment drops below 95 °C, the relief
valve is closed automatically and water flow from the overflow vessel. The pressure
reducer (item 7) on the thermostat valve inlet automatically controls and maintains
constant, stable flow conditions for cold cooling water, regardless of pressure
fluctuations upstream from the valve. A pressure of water from the water supply
system should be reduced to ca. 1.5 bar. A thermal protection device installed
on the cold water inlet prolongs its life, because the valve is protected against
contamination with calcifications caused by hot water leaks. A sump strainer (item
6) must be installed on the cooling water inlet to stop mechanical contaminations,
thus protecting the opening against sediments and other foreign material (e.g.,
small grains of corrosion and metals) which could be deposited in the valve seat
resulting in its failure. A check valve (item 5) protecting against possible water
outflow from the system into the water supply system is installed on the water
supply duct.
In the event of power outage, circulatory pump failure or no heat consumption
by the system, the valve protecting against overheating (item 8) can effectively
cool the boiler to a safe temperature, preventing damage to the boiler and the
system in just few minutes. Reliable function of the temperature sensor is ensured
by two independent thermostat components. Each of them is equipped with its
own sensor and casing. When one of this unit is damaged, the other is still able
to open the valve.
The thermal protection against overheating can only be installed by a
qualified person.
A precondition for an efficient function of the boiler protection against
overheating is a correctly constructed system conforming to current regula-
tions (in accordance with the standard PN-91/B-02413 Heating and heating
systems. Protection systems for water based open vented heating systems.
Requirements), and in particular, meeting the requirements concerning ca-
pacity, equipment, location of an expansion vessel in an open vented system,
minimum diameters, routing and connection systems for protection pipes,
securing protective devices against freezing, and venting of water based
heating system.
