High temperature solar systems
In solar thermal systems with natural circulation in the primary circuit and a water storage with heating jacket, the temperature of the domestic
water in the storage can vary considerably depending on the degree of solar radiation and can reach very high temperatures over long periods.
In summer, and if there is little water usage, the hot water at the
storage outlet can actually reach temperatures around 98°C before
the temperature and pressure safety relief valves are actuated.
At these temperatures, the hot water cannot be used directly,
because of the danger of scalding for users.
Water temperatures over 50°C can cause burns very quickly.
For example, at 55°C, partial burn occurs in about 30 seconds,
whereas at 60°C partial burn occurs in about 5 seconds.
It is therefore necessary to use a thermostatic mixing valve able to:
• reduce the temperature of the water distributed throughout the
domestic water system to a value lower than that in the storage
and suitable for the end user. For reasons of safety, it is
recommended to set the temperature of the mixed water
distributed to the users to values no higher than 50°C;
• keep mixed water temperature constant despite variations in inlet
temperature and pressure.
• continue functioning over time without any loss in performance
and without problems due to the continuously high temperature
of the incoming water;
• enable the high temperature water in the tank to last longer, by
distributing it to the user circuit at a reduced temperature.
• have an anti-scald safety function in case of failure of the cold
water supply.
Operating principle
The thermostatic mixing valve mixes the hot and cold water at the
inlet so as to maintain the mixed water at a constant set temperature
at the outlet. A thermostatic element is fully immersed in the mixed
water outlet passage. It contracts or expands, moving an obturator
which controls the passage of hot or cold water at the inlet. If there
are changes in the inlet temperature or pressure, the internal
element automatically reacts to restore the set temperature at the
outlet.
Construction details
High resistance to temperature
Internal control components are
designed to maintain constant the mixing
valve performance with inlet hot water
temperatures up to 100°C, in continuous
operation.
Anti-scale materials
The materials used in constructing the
mixing valve were selected to eliminate
seizing due to limescale deposits.
All functional parts have been made
using a special anti-scale material with
low friction coefficient, which ensures
over time performance.
Anti-scald safety function
As a safety measure, in case of failure of
the cold water supply, the valve
immediately shuts off the flow of the hot
water. This prevents dangerous burns.
This performance is guaranteed if there
is a minimum temperature difference
between the inlet hot water and the
outlet mixed water of 10°C. Also in case
of failure of the hot water supply, the
valve shuts off the cold water port and
thus the outlet mixed water to prevent
dangerous thermal shocks.
COLD
HOT
MIXED
Code 2527
14
Code 2527
13
Exposure time to cause partial burns
Temperature
Adults
Children 0-5 years
70°C
1 s
--
65°C
2 s
0,5 s
60°C
5 s
1 s
55°C
30 s
10 s
50°C
5 min
2,5 min
