Solution: Heating water analysis according to ÖNORM H 5195

When treating heating water or water in steam systems or water used in cooling systems, the three parts of ÖNORM H5195 must be complied with.

The quality of the heating water is determined by means of an analysis. Sampling and analysis should always be carried out by a specialist company that can demonstrate theoretical and practical knowledge.

ÖNORM H 5195-1

Among other things, the standard deals with damage caused by scale formation in hot water heating systems and provides recommendations for preventing it in accordance with ÖNORM EN 12828. Scale formation—deposits of calcium carbonate on surfaces within the heating system—can result in the following malfunctions and damage:

• Reduction in the heat output of heat transfer surfaces
• Risk of local overheating
• Reduction in cross-section and increase in flow resistance
• Blockage of circulation pumps
• Defects in heat exchangers
• Malfunctions in control or thermostatic valves, etc.

To avoid this, ÖNORM recommends keeping calcium carbonate deposits as low as possible, depending on the water content of the heating system.
The standard also describes the causes and effects of water-side corrosion in
hot water heating systems. In addition to scale formation, corrosion can lead to significant malfunctions in the heating circuit, especially if oxygen enters the heating water. This is supplied with the fresh water feed and can also enter the system through leaks, negative pressure, or non-diffusion-tight pipe materials.

Low pH values, high temperatures, and salt contents > 100 µS/cm also promote corrosion of metallic materials. For aluminum materials, this applies especially to pH values > 8.5. The ÖNORM standard requires additional corrosion protection measures (such as the addition of inhibitors) for chloride contents > 30 mg/l, for example.
Under these conditions, even low oxygen contents can lead to corrosion of metal boilers and pipe materials. Corrosion can result in malfunctions and damage. Corrosion products on heat exchanger surfaces in the boiler, for example, impair heat transfer and increase energy consumption. In addition, local overheating, malfunctions of control or thermostatic valves, increased wear on the circulation pump, or malfunctions of heat meters can result in damage to the boiler.

ÖNORM H 5195-2

This document applies to new installations from the date of publication (2025 06 01).

Heat transfer media for closed heating or cooling systems – Part 2: Heating systems and other systems with frost-protected heat transfer media.

The new ÖNORM

• regulates the properties of glycol-based antifreeze agents and their use in heating systems, air conditioning systems, ventilation systems, cooling systems, solar systems, and heat source systems of heat pumps.
• specifies the measures to be taken to achieve adequate frost protection
• specifies the measures required when using antifreeze agents to prevent corrosion
• provides information on the disposal of water-antifreeze mixtures.