HDG M299, Operation Manual

Page: 68 / 176

4 Planning and installation – Thermal safety device
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4.9 Thermal safety device
In accordance with DIN EN 12828, heating systems must be
equipped with safety devices to prevent the maximum operating
temperature from being exceeded. The safety heat exchanger serves
to protect the boiler against overheating and may not be used for
other purposes (i.e. as a regular heat exchanger). If the heat transfer
capacity is suddenly lost (for example, if the circulation pump for
raising the return temperature fails), heat production cannot be
stopped as quickly as with an oil- or gas-fired boiler. When the
maximum operating temperature is exceeded, the thermal safety
device (TAS) is triggered and cold water flows through the safety
heat exchanger. The excess energy generated is thus dissipated by
this “emergency cooling”. (This is an alternative to fast regulation.)
However, the safety heat exchanger and thermal safety device can
only serve their purpose if the following requirements have been
met:
• A flow pressure of at least two bar and a flow rate of 1800 l/h must
be available at the cold water inlet of the safety heat exchanger.
• The distance between the supply and return lines of the thermal
safety device and the safety heat exchanger should not be less
than their nominal width. The supply line may not be equipped
with a shut-off valve.
• Water must be able to flow freely through the system.
• The flow pressure at the flue pipe connection on the boiler may
not significantly exceed the prescribed value.
The thermal safety device must be installed according to guidelines
from HDG Bavaria.
Mains-dependent, stand-alone supply systems are not safe enough
due to dependence upon the power supply!
The thermal safety device is to be inspected annually by an
authorised, qualified technician to verify that it is functional.
Important!
In order to prevent leaks, avoid turning the connections of the
safety heat exchanger anticlockwise when installing the thermal
safety device.
Important!
The HDG M299/300/350/400 heating system is equipped with two
safety heat exchangers. One is located in the combustion unit and
one in the regular heat exchanger.