Robur GAHP Line AR Series, Installation, Use And Maintenance Manual

Page: 43 / 100

Plumbing installer section
Ed. 2014-08
39
3.5 FILLING OF HYDRAULIC CIRCUIT (to be carried out by installation
technician)
After having completed all the connections of the hydraulic, electrical and gas supply
plants, the hydraulic system installation technician can proceed with filling the hydraulic
circuit, observing the following stages:
You will need: the appliance connected hydraulically and electrically.
1. Activate the automatic air bleeding valves present in the plant;
2. Fill the hydraulic circuit, ensuring the minimum water content in the plant, and
adding, if necessary, to the plant water (free of impurities) a quantity of
monoethylene glycol in proportion with the minimum winter temperature in the
installation zone, as indicated in Table 13, page 40.
3. Bring the plant to the correct pressure, making sure that the pressure of the water in
the plant is not less than 14.5 PSIg and not over 29.0 PSIg.
To facilitate the operation of bleeding air from the hydraulic circuit, the appliance is
equipped with an additional air bleeding valve.
Possible use of glycol antifreeze
Glycols, normally used to lower the freezing point of water, are substances in an
intermediate state of oxidation which, in the presence of oxidizing 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 control
the pH of the solution. A necessary condition for the oxidation of the glycol, and therefore
its degradation, is the presence of an oxidizing agent such as oxygen. In closed circuits in
which no replenishment of water, and therefore of oxygen, occurs over the course of time,
once the oxygen initially 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
adequately 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
mono-ethylene glycol, are not recommended for cooling and heating plants.
The manufacturer does not accept any contractual or extra-contractual liability for
damage caused by the incorrect use or disposal of glycol antifreeze.
It is equally important to recall that the use of monoethylene glycol modifies the thermo
physical characteristics of the water in the plant, and in particular its density, viscosity and
specific average heat. Always check the date of expiry and/or degradation of the product
with the supplier.