Fujitsu NEORE B User Manual Installation Instruction page 27

HEAT PUMP CONNECTION TO HEATING SYSTEM
Designing
The heating system design quality is very improtant, as well as quality of heating water and used materials.
Insufficient flow of heat transfer medium causes increase in condensing temperature and thereby significant
reduction of COP (Coeficient Of Performance). Badly designed regulation system has the same effect. On the
other hand, too high flow causes erosion corrosion attack. Insufficient size of expansion tank is directly related
with possibility of corosion of heating system.
Installation and commissioning
Seemingly insignificant differences between project and realization may lead to malfunction of heating system.
Quality joints, soldering process, rinsing of heating system and first heating are good prerequisite for customer
satisfaction. Cost savings by installing heating system without people with appropriate qualification is intolerable
risk.
Used materials and devices
This problem is associated to project of heating system. Designer should avoid solutions where are used more
materials e.g. copper pipes, aluminium radiators and steel boiler. Such a system can not be protected against
various types of corrosion. Use of certified materials is always preferred. The same applies to seal, flux, solder
etc.. Total corrosion of heating system is very often caused by use of plastic pipes without oxygen barrier for floor
heating.
Heating water quality
Quality of heating water is decisive for long-term and trouble-free operation of heating system. Properties of used
water as heat transfer medium depends on location and type of water supply. It is important to note that water
with properties of drinking water mostly is not suitable to use as heating water without preparation. For heating
systems are important parameters like hardness, salinity, acidity and the content of dissolved gases.
Hardness of water means amount of Ca2+ and Mg2+ salt which during operation conditions changing solubility
and creates practically insoluble carbonates. Limescale forms mostly on bivalent source and negative effects
performs by the following mechanism. Initially creates thin thermal insulating layer. This layer decreases power
of source and also occur local overheating. From unequal dilation at the spot of overheating, compactness layer
is breached. Chipped limescale pieces get into the water and gradually clog refrigerant exchanger and regulation
valves. Carbon dioxide arises during the build up of limescale and causes occurence of air inside of system and
surface corrosion, if the conditions are good. Moreover it is necessery to fill water missing.That is not mostly
adapted and it brings the system into further adverse effects.
Salinity expresses amount of all dissolved salt in water. In practise it is the cations Na+, K+, Fe2+ and anions
Cl- and SO42-. Ions of Fe2+, Cl- a SO42- does not support corrosion of heating system. Water salinity is directly
proportional to its elecctrica conductivity. High values of water salinity helps to electrolytic corrosion especially
when are used more different types of material in heating system (copper, steel).
Acidity of water (pH) is significant criterion for corrosion behavior of system. Because of minimizing corrosion
efficiency, the value of pH of used water should match used materials. It is important to note that pH suitable
for steel is not suitable for example for aluminium etc..
Amount of dissolved gases in water depends on its temperature and pressure of gases. At heating water it is
mainly about dissolved air contains primarily N2, O2 and CO2. From chemical point of view nitrogen in heating
sstem is harmless. But from operation point of view affects adversely. Decreases thermal capacity of water,
increases the compression work and causes cavitation noise. Oxygen and carbon dioxide active corrosion and it
is needed to remove from the water. The most of dissolved gases could be removed from heating system by
bleeding. But it is not possible to remove gases from heating water completely.
If the system is bleeded correctly, a rest of gases in water have do not have got underlying influence to long-term
lifetime and reliability of heating system. Residual oxygen is consumed during corrosion and than corrosion is
stopped. The biggest danger is repeated intrusion of oxygen into system. In practise is this fact the most often
cause of corrosion of system. The reason could be bad tightness of system, wrong parametres of expansion tank,
quality of sealing elements and used plastic parts. Keep in mind that etc. floor heating made from plastic with an
oxygen barrier conforming to norm is not 100% resistent against the diffusion of oxygen. In this case occurs the
oxygen intusion repeatedly corrosion never stops spontaneously. Use of oxygen absorbing component is needed.
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