Product Overview
1
Tmix = Tset + 18°FBY- PASS CLOSING
by-passclosed
system return open
Tf >Tmix≥Ts et +18°F, Tmix=Tr
3
Tf ≤ Tset SYSTEM STARTUP
by-passopen
system return closed
Tf ≤Tset, Tmix=Tf
f
Tmix > Tset + 18°FSYSTEMLOADED
by-passclosed
system return open
Tf >Tmix>Tset +18°F, Tmix=Tr
Tf > Tset STARTOFSYSTEMLOADING
by-passopen
systemreturn open
Tf >Tset, Tr <Tset, Tmix=Tset
2
4
f
f
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
Zone of condensation
forming
Tar deposits
Corrosion
Reduction in heat
exchanger efficiency
Flammability
Primary and
secondary air
Combustion
efficiency
BOILER PROTECTION
VALVE
Accumulation of ash
andresidues
Flue gasand
emission
control
By-pass
from boiler
Return
from system
Mixed
to boiler
Valve body
Spring
Thermostatic
sensor
Plug
Shutter
System return
Temp gauge pocket
wells (4)
1
Tmix = Tset + 18°FBY- PASS CLOSING
by-passclosed
system return open
Tf >Tmix≥Ts et +18°F, Tmix=Tr
3
Tf ≤ Tset SYSTEM STARTUP
by-passopen
system return closed
Tf ≤Tset, Tmix=Tf
f
Tmix > Tset + 18°FSYSTEMLOADED
by-passclosed
system return open
Tf >Tmix>Tset +18°F, Tmix=Tr
Tf > Tset STARTOFSYSTEMLOADING
by-passopen
systemreturn open
Tf >Tset, Tr <Tset, Tmix=Tset
2
4
f
f
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
1
Tmix = Tset + 18°FBY- PASS CLOSING
by-passclosed
system return open
Tf >Tmix≥Ts et +18°F, Tmix=Tr
3
Tf ≤ Tset SYSTEM STARTUP
by-passopen
system return closed
Tf ≤Tset, Tmix=Tf
f
Tmix > Tset + 18°FSYSTEMLOADED
by-passclosed
system return open
Tf >Tmix>Tset +18°F, Tmix=Tr
Tf > Tset STARTOFSYSTEMLOADING
by-passopen
systemreturn open
Tf >Tset, Tr <Tset, Tmix=Tset
2
4
f
f
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
NON-
CONDENSING
BOILER
Wood biomass and condensation build-up
Characteristic components
Wood contains a variable moisture content depending on the type (logs,
pellets, woodchips, etc.). Water vapor is released during the solid fuel
drying phase inside the combustion chamber. The presence of cold
surfaces in the boiler or flue gas chimney can lower the temperature of
the flue gas down to the dew point, causing condensation. Water vapor
condenses on the boiler surfaces, together with soot and part of the
unburnt hydrocarbons contained in the flue gas, producing tar deposits.
These substances stick to the walls of the boiler, covering most of the
inner surfaces. In addition to being dangerous due to its flammability, tar
is damaging to the integrity of the boiler and limits the efficiency of the
flue gas-system waterexchanger.
By keeping the boiler walls at the highest possible temperature,
the boiler protection valve limits the formation of these substances
thereby increasing combustion efficiency, controlling emissions into the
environment and prolonging boiler life.
Operating principle
The thermostatic sensor, completely immersed in the medium, controls
the movement of a shutter that regulates the by-pass flow from the
boiler and toward the system. At boiler startup, the boiler protection
thermostatic mixing valve recirculates the by-pass flow from the boiler
to bring the boiler up to temperature as quickly as possible (fig. 1).
When the by-pass 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 by-pass flow from
the boiler port closes and water returns to the boiler at the same
temperature as the return flow from the system (fig. 3).