Product Overview

COLD
HOT
MIX
32
60
80
100
120
140
160
Kills bacteria instantly
Kills 90% of bacteria in 2 minutes
Kills 90% of bacteria in 2 hours
Optimum temperature
for growth of bacteria
Surviving bacteria inactive
521 “A” model,
NPT male union
Inlet port check valve
detail for 521 “AC”
models NPT male union
Inlet port check valve
detail for 521 “AC”
models sweat union
Construction details
Anti-scale materials
The material used in the construction of the Caleffi MixCal
™
521 series
thermostatic mixing valve reduces jamming caused by lime deposits. All
the working parts such as shutter, seats and slide guides are made of a
special anti-scale material, with a low friction coefficient, assuring long
term performance.
Temperature setting and locking
The control knob permits temperature setting between minimum and
maximum in one turn (360°). It also has a tamper-proof system to lock
the temperature at the set value.
Operating principle
The controlling element of the three-way thermostatic mixing valve is
a thermostatic sensor fully immersed in the mixed water outlet tube
which, as it expands or contracts, continuously establishes the correct
proportion of hot and cold water entering the valve. The regulation of
these flows is by means of a piston sliding in a cylinder between the
hot and cold water passages. Even when there are pressure drops due
to the drawing off of hot or cold water for other uses, or variations in
the incoming temperature, the thermostatic mixing valve automatically
regulates the water flow to obtain the required temperature.
Thermal disinfection
The diagram shows the behavior of the bacteria Legionella Pneumophila
when the temperature conditions of the water in which it is containedvary.
In order to ensure proper thermal “disinfection”, the values must not be
below 140°F.
110
120
130
140
150
160
170
0.11 10 100 1.000 10.000
Seconds
Partial burning
Total burning
Safety condition.
Maximum exposure time
at a given temperature
Temperature — exposure time
Legionella-scalding risk
In systems producing domestic hot water with storage, in order to
avoid the dangerous infection known as Legionella, the hot water must
be stored at a temperature of at least 140°F. At this temperature it is
certain that the growth of the bacteria causing this infection will be
totally eliminated. At this temperature, however, the water cannot be
used directly.
As shown on the diagram opposite, temperatures of more than 120°F
can cause burning very quickly. For example, at 130°F partial burning
will occurr in approximately 30 seconds, while at 140°F partial burning
will occurr in approximately 5 seconds. The time may be reduced by 50
percent or more for children and elderly people.
In view of the above, it is necessary to install a thermostatic mixing valve
which can:
- reduce the temperature at the point of use to a value lower than that
of storage and suitable for sanitary users. For safety reasons, it is
advisable to limit the mixed water temperature to 120°F;
- maintain the temperature constant when the incoming pressure and
temperature conditions vary.