Connection Of The Heat Pump To The Heating System - NeoRe TG Series Installation Manual

8. Design documentation
8.￿ Connection of the heat pump to the heating system
Designing
The impact of the quality of the heating system design is as important as the in￿uence of the quality of water or ma-
terials used. Insuf￿cient heat transfer ￿uid ￿ow leads to an increase in condensation temperature and thus a signi￿cant
deterioration in COP. A poorly designed control system has the same effect. Conversely, high ￿ow rates lead to corrosion
and erosion. Insuf￿cient size of the expansion vessel is directly related to the possibility of corrosion of the heating system.
Installation and commissioning
Seemingly insigni￿cant changes during execution, compared to the project, can lead to the condition that the heating
system is defect-prone. Joint quality, welding and soldering procedures, ￿ushing and ￿rst ￿ring are the cornerstones of user
satisfaction. Installation of the heating system with non-quali￿ed people, in order to save costs, is an intolerable risk.
Used materials and equipment
This issue basically depends on the heating system design. The designer should refrain from solutions where the result is
a material-mixed system, e.g. copper pipes, aluminum radiators, steel boiler. In real life, such a system cannot be protected
against different types of corrosion. It is always worthwhile to use materials with appropriate certi￿cation. This also applies
to auxiliary materials such as seals, ￿uxes and solders. A common cause of overall corrosion of the heating system is the
use of plastic pipes without oxygen barrier for under￿oor heating.
The quality of circulation water
The circulation water quality is decisive for the long-term trouble-free operation of the heating system. The properties
of water used as the heat transfer ￿uid vary different depending on the location of the borehole and water sources. It
is necessary to realize that water, which in all parameters corresponds to drinking quality, usually does not suit heating
systems without treatment. For heating systems, it is important to know parameters such as hardness, salinity, acidity and
dissolved gas content in water.
The water hardness determines the amount of Ca￿+ a Mg￿+ salts contained, which, by varying the solubility under oper-
ating conditions, form virtually insoluble carbonates. Scale is excreted predominantly on the bivalent source and exerts its
negative effects by the following mechanism. At the beginning, it creates a compact thermal insulation layer. This reduces
the overall output of the source and also causes local overheating of the exchanger. Due to uneven dilatation at the over-
heating area, the compactness of the layer is impaired. Pieces of the limescale peel off and get into the circulating water and
gradually clog both the refrigerant exchanger and the control valves. During limescale formation, carbon dioxide is released,
causing aeration of the system and, under favourable conditions, surface corrosion. In addition, it is necessary to replenish
missing water which is largely untreated and re-injects unwanted in￿uences into the system.
The salinity is the sum of all dissolved salts in the water. In practice, these are Na+, K+, Fe￿+ cations and Cl- and SO￿￿-
anions. Fe￿, Cl- and SO￿￿- ions pose danger as they support the heating system corrosion processes. Water salinity is
directly proportional to its electrical conductivity. High water salinity promotes electrolytic corrosion, especially when using
various types of metals (copper, iron).
An important criterion for the corrosion behaviour of the system is its acidity - pH. In order to minimize the corrosive
effect of water, pH should correspond to the materials used. For example, it is important to note that a steel-compliant pH
does not suit aluminum and vice versa.
The content of dissolved gases in water depends on its temperature and gas pressure. For heating water, relevant air
contains mainly N , O a CO
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view has an adverse effect, decreases the temperature capacity of water, increases compression work and causes cavitation
noise. Oxygen and carbon dioxide are corrosive and need to be removed from water. Most of the dissolved gases can be
removed from the heating system by deaerating. However, it is not possible to remove gases from the circulating water
completely.
When properly vented, this is a relatively small amount of gas whose effects do not have a major impact on the long
service life and reliability of the heating system. Residual oxygen and carbon dioxide are consumed in corrosion reactions
and consequently corrosion ceases. The greatest danger is when oxygen enters into the system repeatedly. In practice,
. Nitrogen, from the chemical regime point of view, is harmless, but from the operational point of
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