Anti-condensation valve

CALEFFI
280 series 01223/14 GB
ACCREDITED

ISO 9001 FM 21654 ISO 9001 No. 0003

Replaces dp 01223/11 GB

Function

The anti-condensation valve, used in heating systems with a solid

fuel generator, automatically regulates at the set value the
temperature of the water returning to the generator. Keeping the
generator at a high temperature prevents condensation of the water
vapour contained in the flue gas. It can be used both on boilers and
residential generators such as fireplace heating systems,
thermostoves and thermocookers.
The anti-condensation valve gives the generator a longer life and
ensures greater efficiency.

Product range

280 series Anti-condensation valve sizes DN 20 (3/4”, 1”), DN 25 (1”), DN 32 (1 1/4”)

Technical specifications Dimensions

Materials
Body: - DN 20: brass EN 12165 CW617N
- DN 25, DN 32: brass EN 1982 CB753S
Plug: brass EN 12164 CW614N
Obturator: PSU
Spring: stainless steel
Seal: EPDM
Union seals: non-asbestos fibre
Wax thermostatic sensor

Performance
Medium: water, glycol solutions
Max. percentage of glycol: 50%
Max. working pressure: 10 bar
Working temperature range: 5–100°C
Setting temperatures (Tset): 45°C, 55°C, 60°C, 70°C
Setting accuracy: ±2°C
By-pass complete closing temperature: Tmix=Tset+10°C=Tr

Connections: 3/4” - 1” - 1 1/4” M (ISO 7/1) with union

Code Mass (kg)

● Code completion
Setting 45°C 55°C 60°C 70°C
●
4 5 6 7
Wooden biomass and condensation build-up Characteristic components
Wooden solid fuel contains a variable moisture percentage
depending on the type (logs, pellets, woodchips etc.) and Flow
seasoning. Water vapour is released during the solid fuel drying by-pass
phase inside the combustion chamber. The presence of cold zones
in the generator or flue gas chimney can lower the temperature of
the flue gas down to the dew point, causing condensation to occur.
Water vapour condenses on the generator surfaces, together with
soot and part of the unburnt hydrocarbons contained in the flue
gas, producing deposits and tar. These substances stick to the
walls of the generator, covering most of the inner surfaces. In
addition to being dangerous due to its flammability, tar is damaging
to the integrity of the generator and limits the efficiency of the flue
gas-system water exchanger.
By keeping the generator walls at the highest possible temperature,

to generator
the anti-condensation valve limits the formation of these

Return

System
return
substances, thereby increasing the combustion efficiency,
controlling the emissions into the environment and prolonging the
generator life.

Flue gas and

emission
control

SF 1) Thermostatic sensor 4) Plug

2) Obturator 5) Valve body
3) Spring 6) Temperature gauge holders

Operating principle

The thermostatic sensor (1), completely immersed in the medium,

controls the movement of an obturator (2) that regulates the flows
SR in by-pass (7) and toward the system. At the start-up of the heat
generator, the anti-condensation valve recirculates the flow water
Accumulation of ash ANTI-CONDENSATION so as to bring the generator up to temperature as quickly as
and residues VALVE possible (fig. 1). When the flow temperature Tf exceeds the setting
Primary and Zones of condensation of the anti-condensation valve Tset, the valve’s cold port (8) starts
secondary air: forming: opening to produce the water mixing Tmix: in this phase the system
Combustion loading begins (fig. 2).
Deposits and tar
efficiency When the return temperature to the generator Tmix is greater than
Corrosion
Reduction in heat the setting of the anti-condensation valve by approximately 10°C,
exchanger efficiency the by-pass (7) port closes and water returns to the generator at the
Flammability same temperature as the system return (fig. 3 and fig. 4).

Tf ≤ Tset SYSTEM START UP TRANSIENT 1 Tf > Tset START OF SYSTEM LOADING 2

by-pass open by-pass open
system return closed system return open
Tf ≤ Tset, Tmix=Tf Tf > Tset, Tr < Tset, Tmix=Tset

SOLID Tf SOLID Tf
FUEL FUEL
GENERATOR GENERATOR

Tmix = Tset + 10°C BY-PASS CLOSING 3 Tmix > Tset + 10°C SYSTEM LOADED 4
by-pass closed by-pass closed
system return open system return open
Tf > Tmix = Tset +10°C, Tmix=Tr Tf > Tmix > Tset +10°C, Tmix=Tr

Tf SOLID Tf
SOLID
FUEL FUEL
GENERATOR GENERATOR

Tf = Flow temperature Tmix = Mixed water temperature of generator return

Tset = Anti-condensation setting temperature Tr = System return temperature
Construction details Sizing method / Setting selection

Brass body The valve selection should be made according to the Kv value
The brass body prevents the formation of ferrous residues in the (corresponding to a specific DN body size) and not only according
system, thereby helping to prolong the life of the heat generator. to the thereaded connections. According to the power output and
thermal load on the heat generator, the flow rate provided by the
Thermostatic sensor replacement for setting modification generator can be calculated. With this value, it’s possible to use the
The thermostatic sensor can be easily hydraulic characteristics diagram to obtain the head loss of the
removed for maintenance or setting valve. The sum of the head losses on the valve and head losses of
change. the rest of the system should be compatible with the available head
of the generator pump. The setting (°C) must be selected so as to
Temperature gauge holders guarantee a return temperature to the generator that is high enough
The body of the anti-condensation valve to prevent condensation, also using the information or instructions
in sizes DN 25 and DN 32 features supplied by manufacturers of solid fuel generators.
temperature gauge holders on the front
and rear sides. The holders allow the Installation
housing of code F29571 temperature The valve can be fitted on both sides of the generator in any
gauges for controlling the working position, vertical or horizontal. Installation is recommended on
temperatures of the valve: by-pass water the return to the generator in mixing mode; it is also allowed on
from the flow line, water returning from the flow from the generator in diverter mode.
the system and mixed water returning to
the generator.

Installation in mixing mode (anti-condensation)

Hydraulic characteristics

(m w.g.)

SOLID
FUEL
GENERATOR

Installation in diverter mode

SOLID
(l/min) (m3/h)

FUEL
Flow rate

GENERATOR

Size DN 20 DN 20 DN 25 DN 32
Connections 3/4” 1” 1” 1 1/4”
Kv (m3/h) 3,2 3,2 9 12

Application diagram

Solid fuel generator, direct supply to the system

Safety devices to be chosen Deaerator

according to current regulations
Dirt separator
Pump
Shut-off valve
Expansion vessel
Check valve
Motorised mixing valve
Pressure reducing valve
Filling unit
Backflow preventer
RESIDENTIAL
DEVICE Safety relief valve
Dirt separator for vertical pipes
Deaerator for vertical pipes
Hydraulic separator

Y-strainer
System with inertial storage

Safety devices to be chosen

according to current regulations

M M

SOLID
FUEL
GENERATOR

Solid fuel generator, connection to inertial water storage in parallel.

Safety devices to be chosen

according to current regulations

SOLID
FUEL
GENERATOR

SPECIFICATION SUMMARY
280 series
Anti-condensation valve. Size DN 20 (from DN 20 to DN 32). Connections 3/4” (from 3/4” to 1 1/4”) M (ISO 7/1) with union.
Brass body. Brass plug. PSU obturator. Stainless steel spring. EPDM seal. Wax thermostatic sensor. Medium water and
glycol solutions. Maximum percentage of glycol 50%. Maximum working pressure 10 bar. Working temperature range
5–100°C. Setting temperatures 45°C, 55°C, 60°C, 70°C. Setting accuracy ±2°C. By-pass complete closing temperature
Tset + 10°C.

We reserve the right to change our products and their relevant technical data, contained in this publication, at any time and without prior notice.

Caleffi S.p.A.
S.R. 229 n. 25 · 28010 Fontaneto d’Agogna (NO) · Italy
Tel. +39 0322 8491 · Fax +39 0322 863723
info@caleffi.com · www.caleffi.com
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