Brochure
COLD
HOT
MIX
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.
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.
Construction details
Anti-scale materials
The material used in the construction of the thermostatic
mixing valve eliminates the problem of 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, guaranteeing that the
performance will be maintained over the long term.
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.
Thermal disinfection
The diagram shows the behaviour 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.
Temperature - Exposure time
110
120
130
140
150
160
170
0,1 1 10 100 1.000 10.000 Seconds
Partial burning
Total burning
Safety condition.
Maximum exposure time
at a given temperature
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
Inlet port check valve
detail for 521 "AC"
models NPT male union
Inlet port check valve
detail for 521 "AC"
models Sweat union
521 "A" model,
NPT male union
1/2 inch 3/4 inch 1 inch
Item Description
NPT Sweat NPT Sweat NPT Sweat
521400A, AC 521409A, AC 521500A, AC 521509A, AC 521600A, AC 521609A, AC
521519A, AC 521619A, AC
Union Washer 3 R50055
Union Nut 1" 3 R61008
Male Tailpieces 3 R31981 NA10002 31901A NA10003 59817A* 59834A*
(2 only-'519') (2 only-'619')
Inlet Male Tailpiece
with Check Valve- 2 59893A 59904A 59840A 59905A 59894A 59906A
"AC" Models only
Outlet Tailpiece-
1 R31981 NA10002 31901A NA10003 59817A* 59834A*
"AC" Models only
Outlet Adapter with
1 ---- ---- ---- NA10056 ---- NA10058
temperature gage
* Tailpiece fitting with integral union nut. 1" NPT and Sweat models require only 2 separate 1" union nuts (R61008)
Item Qty
per Valve