Airwell AW-WHPMA18-H93 Manual De Instalación página 34

9.4.4 Water circuit anti-freeze protection
Ice formation can cause damage to the hydraulic system.
As the outdoor unit may be exposed to sub-zero
temperatures, care must be taken to prevent freezing of
the system.
All internal hydronic parts are insulated to reduce heat
loss. Insulation must also be added to the field piping.
The software contains special functions using the heat
pump to protect the entire system against freezing. When
the temperature of the water flow in the system drops to
a certain value, the unit will heat the water, either using
the heat pump, the electric heating tap, or the backup
heater. The freeze protection function will turn off only
when the temperature increases to a certain value.
In event of a power failure, the above features would not
protect the unit from freezing.
Do one of the following to protect the water circuit
against freezing:
▪ Add glycol to the water. Glycol lowers the freezing
point of the water.
▪
Install freeze protection valves. Freeze protection
valves drain the water from the system before it can
freeze.
NOTE
If you add glycol to the water, do NOT install
freeze protection valves. Possible conse-
quence: Glycol leaking out of the freeze
protection valves.
1. Freeze protection by glycol
About freeze protection by glycol
Adding glycol to the water lowers the freezing point of water.
WARNING
Ethylene glycol is toxic.
Ethylene Glycol
Quality of
Cooling capacity
glycol
modification
0% 1.000
10% 0.984
20% 0.973
30% 0.965
Propylene Glycol
Quality of
Cooling capacity
glycol
modification
0% 1.000
10% 0.976
20% 0.961
30% 0.948
Due to the presence of glycol, corrosion of the system is
possible. Uninhibited glycol will turn acidic under the
influence of oxygen. This process is accelerated by the
presence of copper and high temperatures. The acidic
uninhibited glycol attacks metal surfaces and forms
galvanic corrosion cells that cause severe damage to the
system. Therefore it is important that:
▪ the water treatment is correctly executed by a qualified
water specialist,
▪ a glycol with corrosion inhibitors is selected to counteract
acids formed by the oxidation of glycols,
▪ no automotive glycol is used because their corrosion
inhibitors have a limited lifetime and contain silicates which
can foul or plug the system,
▪ galvanized pipes are NOT used in glycol systems since
the presence may lead to the precipitation of certain
components in the glycol's corrosion inhibitor.
Glycol absorbs water from its environment. Therefore do
NOT add glycol that has been exposed to air. Leaving the
cap off the glycol container causes the concentration of
water to increase. The glycol concentration is then lower
than assumed. As a result, the hydraulic components
might freeze up after all. Take preventive actions to ensure
a minimal exposure of the glycol to air.
Types of glycol
The types of glycol that can be used depend on whether the
system contains a domestic hot water tank:
If the system contains a domestic hot water tank, then only
use propylene glycol*;
If the system does NOT contain a domestic hot water tank,
then you can use either propylene glycol* or ethylene glycol;
*Propylene glycol, including the necessary inhibitors, classified as
Category III according to EN1717.
Required concentration of glycol
The required concentration of glycol depends on the lowest
expected outdoor temperature, and on whether you want to
protect the system from bursting or from freezing. To prevent
the system from freezing, more glycol is required.
Add glycol according to the table below:
Modification coefficient
Power Water
modification resistance
1.000 1.000
0.998 1.118
0.995 1.268
0.992 1.482
Modification coefficient
Power Water
modification resistance
1.000 1.000
1.071
0.996
0.992 1.189
0.988 1.380
30
WARNING
NOTE
Minimum
outdoor
Water flow
temperature
modification
1.000 0℃
1.019 -5℃
1.051 -15℃
1.092 -25℃
Minimum
outdoor
Water flow
temperature
modification
1.000 0℃
1.000 -4℃
1.016 -12℃
1.034 -20℃