Product Overview

Operating principle
The thermostatic sensor, completely immersed in the medium,
controls the movement of a shutter that regulates the bypass flow
from the boiler and toward the system. At boiler startup, the boiler
protection thermostatic mixing valve recirculates the bypass flow
from the boiler to bring the boiler up to temperature as quickly as
possible (fig. 1). When the bypass flow from the boiler Tf exceeds the
setting of the boiler protection mixing valve Tset, the valve’s return
from the system port starts opening to produce the water mixing
Tmix: in this phase the system loading begins (fig. 2).
When the mixed flow to the boiler temperature Tmix is greater than
the set point of the boiler protection mixing valve by approximately
18°F (10°C), the bypass flow from the boiler port closes and water
returns to the boiler at the same temperature as the return flow from
the system.
Characteristic components
Bypass
from boiler
Return
from system
Mixed
to boiler
Valve body
Spring
Thermostatic
sensor
Plug
Shutter
System return
1
Tmix = Tset + 18°F BY-PASS CLOSING
by-pass closed
system return open
Tf > Tmix = Tset +18°F , Tmix=Tr
3
Tf ≤ Tset SYSTEM START UP
by-pass open
system return closed
Tf ≤ Tset, Tmix=Tf
Construction details
SOLID
FUEL
BOILER
SOLID
FUEL
BOILER
f
f
Tf=Bypass flow from boiler Tmix=Mixed flow to boiler temperature
Tset=Boiler protection valve set point temperature Tr=Return from system temperature
Tmix > Tset + 18°F SYSTEM LOADED
by-pass closed
system return open
Tf > Tmix > Tset +18°F , Tmix=Tr
Tf > Tset START OF SYSTEM LOAD ING
by-pass open
system return open
Tf > Tset, Tr < Tset, Tmix=Tset
2
4
f
f
SOLID
FUEL
BOILER
SOLID
FUEL
BOILER
Flow curve
lowrate
The brass body prevents the formation of ferrous residues in the
system, prolonging boiler operating life.
The thermostatic sensor can be easily replaced
for maintenance or set point change.
The boiler protection mixing valve body features
temperature gage pocket wells on front and rear
sides, allowing installation of a temperature
gage (code F29571) for monitoring the working
temperatures: bypass from boiler, return from
system, and mixed to boiler.
Temp gage pocket
wells (4)
1”
1-1/4”
F
.
.
.
.
.
.
.
4.5
7
4.3
3
1.5
0.7
p (psi)
21
(l/min)
(gpm)
2
4
10
20
200
88
44
22
9
Cv: size 1”... 10
size 1-1/4“ ... 14
51