Thermal safety
A thermal discharge safety device (TAS) is an autonomous safety fitting for a solid fuel boiler . The thermal discharge safety device has the task of dissipating the heat by supplying cold water if the flow temperature of the boiler is too high. The TAS works without auxiliary energy and therefore especially when z. B. in the event of a power failure, the heating pump does not work.
There are the following variants:
- In a hot water heater that is directly heated with solid fuel , a drain valve in the drinking or hot water flow is opened so that the water is forcibly drained.
- As a protective device against residual heat in closed heating circuits or if the heating pump fails, many boilers use a heat exchanger , e.g. B. a coil built into the water space of the boiler. The flow of this heat exchanger ends unblockably in the wastewater. When the temperature sensor responds, fresh water is passed through the heat exchanger so that the heat is removed from the boiler.
- If the boiler does not have a heat exchanger, the fresh water must be fed into the heating circuit and drained off after flowing through the boiler. There are also two-way valves that are located directly in the flow on the boiler and have a connection to the return. This solution cools more effectively, but brings oxygen into the heating circuit with the fresh water. Corrosion protection and frost protection additives may be lost.
The TAS consists of a sensor on a capillary tube or directly on the valve, a shut-off valve and a drinking water connection (TW). The expansion of the capillary liquid of the sensor opens the shut-off valve at approx. 95 ° C against a spring force and thus releases the drinking water connection. The drinking water absorbs the excess heat and is discharged as heated water by means of an overflow and a discharge line.
As a rule, the further supply of fuel or its burn-off is first interrupted by a safety temperature limiter. The TAS then only has the task of absorbing the residual heat and avoiding an unacceptable rise in temperature. The energy stored in the boiler comes from the remaining unburned fuel and the latent heat of the brickwork. The boiler equipment corresponds to DIN 4751 T2.