To prevent icing in the primary circuit during winter time, the appliance is provided •
with antifreeze functions activating the water circulation pump of the primary cir-
cuit (if controlled by the appliance) and the burner of the appliance itself (when
necessary). It is therefore necessary to ensure a permanent supply of electricity
and gas to the appliance throughout the whole winter period. If it is not possible
to ensure a permanent supply of electricity and gas to the appliance, use glycol
antifreeze of the inhibited monoethylene type.
If glycol antifreeze is to be used, DO NOT USE galvanised pipes, as they are poten-•
tially subject to corrosion in the presence of glycol.
Glycols, normally used to lower the freezing point of water, are substances in an inter-
mediate state of oxidation which, in the presence of oxidising agents such as oxygen,
are transformed into corresponding acids. This transformation into acids increases the
corrosive nature of the fluid contained in the circuit. For this reason, mixtures that are
commercially available almost always contain inhibiting substances that are able to con-
trol the pH of the solution. A condition necessary for the oxidation and degradation of
glycol is the presence of an oxidising agent such as oxygen. In closed circuits in which no
replenishment of water (and therefore of oxygen) occurs over time, once the oxygen ini-
tially present has reacted, the degenerative phenomenon of glycol is hugely inhibited.
Most circuits, however, are of the non-sealed type, and therefore receive a more or less
continuous supply of oxygen.
Therefore it is essential, whatever type of glycol is in question, to verify that it is ade-
quately inhibited and that the necessary checks are regularly performed during its entire
period of use.
Antifreeze liquids for cars, which do not contain inhibiting components other than ethyl-
ene glycol, are not recommended for cooling and heating plants.
The manufacturer does not accept any contractual or extra-contractual liability for
damages caused by the use or disposal of glycol antifreeze.
It is equally important to recall that the use of monoethylene glycol modifies the ther-
mophysical characteristics of the water in the plant, and in particular its density, viscosity
and average specific heat. Always check the date of expiry and/or degradation of the
product with the supplier.
In the Table 4.2 Technical data for filling the hydraulic circuit → 27 the approximate freez-
ing temperature of the water-glycol mixture and the consequent increase in pressure
drops of the appliance are shown, according to the percentage of monoethylene glycol.
This Table 4.2 Technical data for filling the hydraulic circuit → 27 should be taken into
account for the sizing of the pipes and the circulation pump (for calculation of internal
pressure drops of the appliance, refer to the Table 2.1 GAHP-A LT technical data → 9 or
Table 2.2 GAHP-A HT technical data → 10).
Nevertheless, it is advisable to consult the technical specifications of the monoethylene
glycol used. If automatic loading systems are used, a seasonal check of the quantity of
glycol present in the plant is also necessary.
Table 4.2 – Technical data for filling the hydraulic circuit
% of MONOETHYLENE GLYCOL 10 15 20 25 30 35 40
WATER-GLYCOL MIXTURE FREEZING TEMPERATURE -3°C -5°C -8°C -12°C -15°C -20°C -25°C
PERCENTAGE OF INCREASE IN PRESSURE DROPS -- 6% 8% 10% 12% 14% 16%
LOSS OF EFFICIENCY OF UNIT -- 0,5% 1% 2% 2,5% 3% 4%
If the percentage of glycol is ≥ 30% (for ethylene glycol) or ≥ 20% (for propylene glycol):
