Immergas EOLO Eco Series Guide

1
STEEkW ed 12/03 EOLO Eco kW
Technical Documentation Technical Documentation
EOLO Eco 24-28 kW
Instantaneous wall-hung room-sealed fan-
assisted boiler with low emission of polluting
gases
EOLO Eco 24 kW
EOLO Eco 28 kW
EOLO Eco Kw is a room-sealed, fan-assisted wall-mounted
generator characterised by low polluting emissions that con-
form with the requirements of the most ecological class (class
5) established by European standards (UNI EN 297 and EN
483).
ese results are possible thanks to the special water cooled
vertical Venturi burner.
ere are two versions in the range, one with a power of 24
kW (20,640 kcal/h) and one with a power of 28 kW (24,080
kcal/h).
e regulation and the control functions are managed by an
electronic control board microprocessor drive.
anks to which the appliance can be connected to the Amico
Remote Control.
e boiler features a standard antifreeze safety device that
protects it against temperatures as low as -5°C (optional as
low as -15°C).
e hydraulic circuit features a copper water-gas
exchanger as well as a new hydraulic unit in a compound
material.
Besides the pump and 3-way electric diverter valve, that,
depending on needs, lets boiler water circulate in the central
heating system or in a stainless steel plate exchanger for the
instant production of domestic hot water, this unit also
houses the devices that control the hydraulic circuit (system
absolute pressure switch, system adjustable by-pass, etc.).
Combustion air ow into the sealed chamber and ue
extraction are ensured by a fan; the correct operation of
which is controlled by a dierential pressure switch.
General features.
e boiler functioning parameters are set by turning the control
panel knobs.
e functioning status and possible anomalies are easily signal-
led by leds on the panel.

2
STEEkW ed 12/03 EOLO Eco kW
3
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
EOLO Eco kW Main dimensions and connections.
Legend:
G - Gas supply
AC - D.h.w. outlet
AF - D.h.w. (cold) inlet
R - System return
M - System delivery
V - Electrical connection
EOLO Eco kW Control panel.
Legend:
1 - Stand by LED
2 - Burner on LED
3 - D.h.w. on LED
4 - Central heating on LED
5 - Temperature LED – Ignition stop malfunction
6 - Temperature LED – Flue pressure switch malfunction
7 - Temperature LED – System pressure insucient malfunction
8 - Temperature LED – Circulation insucient malfunction
9 - Temperature LED – Delivery probe faulty
10 - Temperature LED – Domestic hot water probe faulty
11 - Temperature LED – Overheating lock
12 - Stand-by-D.h.w./Remote Control (CAR)-D.h.w. and Heating-Reset-
selector switch
13 - D.h.w. temperature knob
14 - Central heating temperature knob
15 - Boiler manometer
Height (mm) Width (mm) Depth (mm)
830 440 350
CONNECTIONS
GAS DOMESTIC
HOT WATER SYSTEM
G AC AF R M
1/2” 1/2” 1/2” 3/4” 3/4”

2
STEEkW ed 12/03 EOLO Eco kW
3
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
EOLO Eco kW main components.
Legend:
1 - Gas valve
2 - D.h.w. NTC probe
3 - D.h.w. ow switch
4 - D.h.w. heat exchanger
5 - Burner
6 - Ignition electrodes
7 - Combustion chamber
8 - Sealed chamber
9 - Fan
10 - Intake traps (air A) - (ues F)
11 - Positive signal pressure point
12 - Negative signal pressure point
13 - Flue pressure switch
14 - Draught diverter
15 - Delivery probe
16 - Overheating safety thermostat
17 - Primary exchanger
18 - System expansion vessel
19 - Automatic air vent
20 - Circulator
21 - ree-way valve (motorized)
22 - System pressure switch
23 - Safety valve 3 bar
24 - System drainage cock
25 - System lling valve

4
STEEkW ed 12/03 EOLO Eco kW
5
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Hot water for central heating and domestic use is produced
by a primary and secondary (d.h.w.) circuit that are engaged
according to requirements.
EOLO Eco kW hydraulic diagram.
Legend:
1 - D.H.W. ow switch
2 - D.H.W. NTC probe
3 - D.H.W. heat exchanger
4 - Gas valve
5 - Burner
6 - Primary exchanger
7 - Draught diverter
8 - Fan
9 - Sealed chamber
10 - Flue pressure switch
11 - Delivery probe
12 - Overheating safety thermostat
13 - System expansion vessel
14 - Automatic air vent
15 - Circulator
16 - ree-way valve (motorized)
17 - System draining cock
18 - System lling valve
19 - Adjustable by-pass
20 - System pressure switch
21 - 3-bar safety valve
22 - Flow limiter
G - Gas supply
AC - D.h.w. outlet
AF - D.h.w. (cold) inlet
R - System return
M - System delivery

4
STEEkW ed 12/03 EOLO Eco kW
5
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Primary circuit (boiler circuit).
e primary circuit with relevant control and safety devices
is triggered each time there is a request for central heating
or domestic hot water.
Operation.
e heat contained in the ue produced by combustion is ab-
sorbed by the copper blades of the primary water-gas exchanger
(7) which, in turn, transfers it to the water circulating inside
it by means of the boiler pump (15).
e water is transferred directly into the system or else can
be diverted inside the stainless steel instantaneous plate ex-
changer (3).
is depends on the position of the motorised 3-way valve
(16) which, when idle, lets the water ow through the d.h.w.
exchanger (3); on the other hand, when responding to a heating
request, the ow is diverted to the system delivery (M) and
return (R) pipes.
Flow-head graph.
e trend of the curve that represents the system’s ow-head
ratio depends on how fast the pump is working and on how
the system by-pass is adjusted. Depending on the position,
it provides the system with a higher or a smaller head. e
characteristic curves are shown in the following graphs.
Head (kPa)
Flow rate Litres/h
A
A = Head available to the system on maximum speed with the by-pass o
(adjustment screw fully tightened)
B = Head available to the system on maximum speed (screw tightened
1.5 turns compared to the adjustment screw completely loose)
C = Head available to the system on maximum speed with the by-pass
open (adjustment screw completely loose)
Head (m H2O)
Boiler circulator (1).
It works on the primary circuit return, located immediately
after the 3-way diverter valve to which it is connected.
It is part of the integrated multi-function unit made in a
compound material.
A space on the body houses the automatic air vent (2).
Primary exchanger (1).
It is a water-gas lamellar exchanger with copper pipes and ns
(N° 75 ns 24 kW version) (N° 98 ns 28 kW version). e
central heating delivery NTC probe (2) and the overheating
safety thermostat (3) are located on the exchanger’s outlet
(delivery).
e four pipes it is made of are connected in series (4).
It is connected to the pump delivery and primary circuit deli-
very by means of pipes with threaded ttings.
Delivery
Return
1
34
2
EOLO Eco 24 kW
Head (kPa)
Flow rate Litres/h
Head (m H2O)
EOLO Eco 28 kW
B
C
A
B
C

6
STEEkW ed 12/03 EOLO Eco kW
7
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
25
1
34
Circulator
delivery
System
return
CIRCULATOR
RETURN
SYSTEM
RETURN
D.H.W.
EXCHANGER
RETURN
Motorised 3-way diverter valve.
Whenever a request is made (for domestic hot water or central
heating) thanks to this 3-way electric diverter valve, working on
the primary circuit return, boiler water is transferred either to
the heating system or to the d.h.w. exchanger (plate type).
is depends on the position of the shutter (5) which shuts
o passage to the system and simultaneously opens the way
to the d.h.w. exchanger (domestic hot water position) or, vice
versa (central heating position).
is shutter (5) is moved in either position by powering the
motor (1).
e hydraulic part of the boiler consists of a unit made in a
composite material (2) that also includes the circulator and it is
operated by a motor (1) which causes it to move as required.
Operation.
When the central heating or domestic hot water position has
to be reached the motor (1) is switched on by the integrated
board.
Each time the motor turns of 180° it causes the shutter (5) to
move and it compresses (central heating position) or releases the
shutter’s contrast spring (4) (domestic hot water position).
Both the spring (4) and shutter (5) are inside the 3-way car-
tridge (3).
When the position requested is reached hydraulically, one of
two limit switches (6) located inside the motor box (1) opens
and closes alternately.
When idle, the shutter (5) is positioned in d.h.w. functio-
ning.
Each time an heating request is satised the motor (1) turns
and releases the shutter's contrast spring (4).
On the contrary, at the end of each d.h.w. request, the shutter
(5) remains in the position reached.

6
STEEkW ed 12/03 EOLO Eco kW
7
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Safety devices and checks.
Adjustable system by-pass (2).
is device guarantees the circulation of water in the primary
circuit (between delivery and return) even when it would be
prevented by the high resistance of the system.
It is mounted on the delivery manifold (1) and adjusted by a
screw that can be accessed from the bottom of the valve sup-
porting plate.
System lling unit (3).
is is a ball cock located between the boiler circuit and the
domestic cold water inlet and it makes possible to pressurise
the central heating system.
e cock is connected to a lling up tting (4) which, in turn,
is connected to the motorised 3-way diverter valve unit.
System pressure switch (5).
is switch detects the pressure inside the primary circuit. It
is housed in the delivery manifold unit (1) and coupled to a
microswitch that prevents the burner working when the pres-
sure measured is below 0.3 bar.
It prevents the primary exchanger overheating.
Automatic air vent (6).
It automatically expels any gaseous substances from the boiler
circuit.
It is mounted on the circulator delivery, directly on the hy-
draulic unit.
Safety valve 3 bar (7).
It prevents the safety pressure being exceeded in the primary
circuit (3 bar).
It is located at the front of the delivery manifold unit (1) and
xed on the outside by a fork.
When this valve trips it causes water to come out through the
delivery pipe.
System expansion vessel (8).
It compensates the changes in volume following the heating
of water and permits to reduce pressure changes.
It has a useful capacity of 7.4 litres and a pre-load pressure
of 1.0 bar.
It is located at the back of the appliance.
System
delivery
2
1
4
6
3
7
5
1
8

8
STEEkW ed 12/03 EOLO Eco kW
9
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Secondary circuit (domestic hot water circuit).
Operation.
Running the domestic hot water causes cold water to ow
through the d.h.w. ow switch (1) and, as a result, the electrical
contact connected to it closes (see the electrical circuit).
After this, the integrated board starts the domestic hot water
priority function phase whereby the burner is ignited and, if
there is an on-going central heating request, the 3-way diverter
valve (2) switches and moves into the working position (see
operation of the 3-way hydraulic diverter valve).
is causes the return pipe (R) to close and the simultaneous
opening of the passage to the d.h.w. exchanger (3).
is prevents circulation in the central heating system while
it is allowed in the plate exchanger inside which the domestic
cold water absorbs the heat contained in the primary circuit
water (see d.h.w. exchanger).
is means that the central heating function is o in this phase,
the production of domestic hot water having priority.
e water-water heat exchange takes place inside the d.h.w.
exchanger (3) which is xed with screws to the d.h.w. outlet
body (1) and to the d.h.w. inlet body (2).
e part at the top of the left body allows the delivery water to
enter the primary circuit while the part at the bottom allows
the domestic hot water to exit.
Likewise, the top of the right body allows the domestic cold
water to enter while at the bottom, return of the primary
circuit.
e d.h.w. probe (4), by means of which the integrated board
is able to measure the temperature of the domestic hot water,
is mounted on the domestic hot water outlet body (1).
Primary circuit
delivery
Primary circuit
return
4
1
3
2
Primary circuit
delivery
Primary circuit
return
Domestic hot water
outlet
Domestic cold water
inlet

8
STEEkW ed 12/03 EOLO Eco kW
9
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
1
2
1
1
Primary
circuit
delivery
Primary
circuit
return
D.h.w. ow switch (1).
Running the domestic hot water at a ow rate of at least
2.0 l/min and a dynamic pressure of 0.3 bar, the d.h.w. ow
switch (1) enables the boiler to work in the domestic hot
water phase.
is takes place by means of a magnet that, upon lifting when
it is hit by the ow of domestic cold water, moves closer to
an electrical contact (reed relay) causing it to move due to the
magnetic eect.
When the contact closes, located outside the pipe through
which the water ows, it enables the integrated board to start
the domestic hot water priority functioning phase.
It is xed with a pin to the valve supporting plate.
A ow limiting device (2) is mounted on the outlet of the
d.h.w. ow switch, 7.55 l/min (24 kW version) and 9.0 l/min
(28 kW version).
D.h.w. exchanger.
is is a water-water exchanger consisting of stainless steel
plates placed on top of each other (16 in the 24 kW version
and 20 in the 28 kW version) on the surface of which ows,
in counter current, the water of the boiler circuit and the
domestic cold water and through which heat exchange occurs
between the two liquids.
For the hydraulic coupling four O rings (1) are used that al-
low direct coupling to the d.h.w. inlet body and to the d.h.w.
outlet body.
D.h.w.
outlet D.c.w.
inlet
Domestic cold water
inlet

10
STEEkW ed 12/03 EOLO Eco kW
11
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
is circuit consists of an atmospheric burner and a modulating
gas valve that permit, respectively, the combustion of gas and
the regulation of its ow rate.
Operation.
When the main coils (3) are energised, both inner valve shutters
open, allowing the gas to ow towards the burner.
e ow rate/outlet pressure is regulated by means of the gas
valve stabiliser and the modulation coil (1).
e burner nozzles (7) inject the fuel into the vertical Venturi
pipes (ramps) inside which an optimum air-gas mix is obtained
which, during combustion, minimises secondary air require-
ments. e spark from the ignition electrodes (8-9) ignites
the burner that, working with a “low” ame on the whole
surface, ensures combustion at temperatures that are lower
than those with traditional burners. is all helps to reduce the
emissions of oxides of nitrogen (NOx) and carbon monoxide
(CO) considerably.
Modulating gas valve.
e gas valve (SIT 845) features two main coils (3) and a
modulation coil (1) controlled by the integrated board.
e maximum and minimum outlet pressure settings can be
made on this valve (see gas regulations).
Main electrical coils (3).
ey are two ON-OFF type coils energised (230 Vac) by the
integrated board when the burner has to be ignited.
ey are electrically connected in parallel and energised by
mains power through a special connector (2).
Modulation coil (1).
is low-voltage coil is controlled by the integrated board.
It controls the gas valve stabiliser and is used to change the
outlet pressure in a way proportionate to the dc current that
runs through it.
Gas circuit.
Burner (4).
e burner consists of two rows of 12 (24 kW version) and 14
(28 kW version) vertical Venturi pipes (5) inside which gas is
injected by an equal number of nozzles (7) mounted on the
special, aluminium manifold (6). e diameter of the nozzles
(7) varies according to the type of gas utilised (see technical
data). At the top, the return pipe of the primary circuit water
travels across the top of it lengthways, cooling it down when
it is working. is is necessary because the combustion with a
low ame and the reduced quantity of air tend to increase the
burner surface temperature.
A diaphragm plate (11) is xed to the burner (4) that improves
ignition, optimising the ow of gas and air.
Ignition occurs thanks to an integrated electronic board
that controls both the ignition (8-9) and detection (10)
electrodes.
Ignition electrode (8).
It is controlled by the integrated board that produces an
electric discharge between its end and the earthed electrode
(dummy) (9).
ey are located on the left side of the burner.
Detection electrode (10).
It is controlled by the integrated board and detects burner
ignition.
It is located on the burner side opposite to the ignition elec-
trode.
11
8
10
4
7
6
9
5
3
± 0,5
5
± 1

10
STEEkW ed 12/03 EOLO Eco kW
11
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Gas adjustments.
e maximum and the minimum gas pressure adjustments
can be made on the gas valve respecting the values shown in
the heat outputs table, in function of the model and the gas
type (see technical data).
Measurements are made using a dierential manometer con-
necting it'swhose positive pressure point to the gas valve outlet
(4) and it's negative pressure point to the positive pressure
point in the ange with traps located at the top of the sealed
chamber (see gure).
Legend:
1 - Modulation coil
2 - Minimum output adjustment
3 - Maximum output adjustment nut
4 - Gas valve outlet pressure point
5 - Gas valve inlet pressure point
6 - Protection cap
Valve SIT 845
SIT 845 gas valve
Adjustment maximum pressure.
Run o some domestic hot water after having set its tempera-
ture selector on maximum.
Turn the brass nut (3) clockwise to increase pressure to the
burner and counter clockwise to reduce it.
Adjustment minimum pressure
(to be done after the adjustment maximum pressure).
After having cut electrical power to the modulation coil, turn
the screw (2) clockwise to increase pressure to the burner and
anticlockwise to reduce it.
Gas conversion.
ere are special kits to adapt the boiler to a gas type dierent
to the one for which the boiler is set as standard (natural gas
or LPG).
Conversion consists in changing the burner nozzles and moving
the gas type selector “NATURAL GAS – LPG” (S8) on the
integrated board.
Maximum and minimum pressures are then regulated on the
gas valve as described above.
e maximum and minimum output setting in the central
heating phase can be set via the parameters (see integrated
board operation).
e burner ignition pressure is not regulated because the
type of board operation does not require such a setting (see
integrated board operation).

12
STEEkW ed 12/03 EOLO Eco kW
13
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Flue circuit.
Operation.
e products of combustion, after having hit the water-gas
exchanger (2), are slowed down and distributed by the plate
(12) thus increasing combustion eciency. ey are then
conveyed to a draught diverter (4) on top of which the ue
extractor (fan) (5) is mounted.
Fan operation ensures forced expulsion of the ue and, at the
same time creates a vacuum in the sealed chamber (3) so the
combustion air can be extracted from outside.
Correct fume extraction is controlled by a dierential ue pres-
sure switch (6) that enables or prevents burner ignition.
Air-ue intake traps (7-8).
e top outer part of the sealed chamber features two intake
traps with screw closing, accessible from the front and from
where combustion air (7) and ue (8) can be sampled.
Flue pressure switch signal pressure points (9-10).
e top outer part of the sealed chamber features two pressure
points with screw closing by means of which it is possible to
measure the signal on the ends of the ue pressure switch
(6).
e negative pressure point (9) is connected to a “Y” shaped
pipe (11) which, in turn, is connected to the negative pressure
point of the ue pressure switch (6) and to the pressure point
positioned at the outlet of the Venturi pipe inserted in the
fan’s exhaust terminal.
e positive pressure point (10) is connected directly to the
inside of the sealed chamber.
Flue pressure switch (6).
It is located at the top inside the sealed chamber and detects, by
means of the relative points, the dierence in pressure between
the outlet of the Venturi pipe inserted in the fan exhaust
(negative signal) and the inside of the sealed chamber
(positive signal).
e signal measured by the pressure switch is variable accord-
ing to the length of the air inlet/exhaust terminals and can be
11
2
12
6
4
10
9
8
7
5

12
STEEkW ed 12/03 EOLO Eco kW
13
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
measured by the relative pressure points located at the top of
the sealed chamber (9-10).
When it triggers it causes a switch to close (S6) that acts on the
integrated board enabling or preventing burner ignition.
Flue pressure switch
triggering pressures
ON
Pa (mm H2O)
ON
Pa (mm H2O)
EOLO Eco kW 150 (15.3) 130 (13.26)
Fan (5).
e extractor operates downstream from the combustion
chamber and is xed vertically to the top of the draught diverter
(4) from where it extracts the ue and conveys them to the ex-
haust pipes to which the boiler is connected. It simultaneously
guarantees the ow of air inside the sealed chamber.
A venturi pipe is inserted inside the fan outlet terminal pipe
(1); the negative signal of the pressure switch (6) is detected
on the Venturi pipe outlet.
It is controlled by the integrated board and its operation co-
incides essentially with that of the burner.
Air inlet and exhaust systems.
(see air inlet and exhaust terminal instructions).
EOLO Eco kW is connected to the push-tting air inlet/
exhaust pipes and can be installed either with a fan-assisted
sealed chamber (type C) conguration or, by means of the
relative kit, the fan-assisted open chamber conguration
(type B22).
Fan-assisted, open chamber conguration
(type B22) for installing outdoors in a partially
protected place.
Using a specic kit, the EOLO Eco kW boiler can be installed
outdoors in a partly sheltered place.
In this way, the appliance works in the fan-assisted open
chamber conguration (type B22) so the combustion air can
be taken directly from the environment.
Inlet.
Air inlet is possible through holes present on the external
surface of the ange (2).
e ange must be mounted on the central hole in the upper
side of the sealed chamber after inserting the respective gasket
(1) and xing it through the 4 screws.
On the ange (2) it is necessary to install the cover cap Ø180
(3) through the two self-tapping screws, combining the two
holes present on the cover cap and on the ange.

14
STEEkW ed 12/03 EOLO Eco kW
15
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
1
2
3
5
4
6
7
Exhaust.
e connection between the Ø 80 mm outlet pipes is realized
by push-tting with the respective ange (2), which seal is
provided by special lip gaskets.
With specic accessories it is possible to have an horizontal
(A) or a vertical (B) exhaust.
In order to prevent problems due to condensation, the outlet
pipes must not exceed 5 m lenght for standard pipes and 12
m lenght for insulated pipes.
Maximum straigth horizontal lenght is 12 m.
For the correct functioning of the boiler working in B22 con-
guration, it is necessary to set the ue shutter on position "5"
(see instruction manual of the boiler).
Fan-assisted, sealed chamber conguration
(type C).
Exhaust.
Connection to the exhaust pipes is by means of a ange (1) or
a anged bend to connect to tting (4) on top of the sealed
chamber, placing a special shaped seal in between (6).
e ange diers according to whether the split or concentric
system is used.
In the rst case, the passage for the air inlet of combustion air
(5) is closed while, in the second case, it is used.
e ue shutter (7) is mounted on the exhaust tting (4) which
has to be adjusted to ensure correct boiler operation.
e appropriate adjustment depends on the type of pipe used
and its length (see boiler instruction handbook).
To adjust, unscrew the front stop screw and move the gradu-
ated indicator to the correct position, aligning the value to the
horizontal reference.
Air inlet.
Using the split system, connection to the air inlet pipes is
exactly the same as for the exhaust pipes, connecting to the 80
mm diameter hole (2) at the top of the sealed chamber.
e unused hole is closed with one of the caps (3) supplied
with the boiler.
If coaxial pipes are used, air inlet occurs by using the concentric
hole outside the exhaust pipe (5).
Air inlet/ ue exhaust kits
(See EOLO Maior kW).
Couple-on horizontal concentric kit 60/100
(See EOLO Maior kW).
Couple-on horizontal concentric kit 80/125
(See EOLO Maior kW).
Couple-on vertical concentric terminal kit 60/100
(See EOLO Maior kW).
Couple-on vertical concentric terminal kit 80/125
(See EOLO Maior kW).
Couple-on separator kit 80/80 and 80/80 insulated
(See EOLO Maior kW).

14
STEEkW ed 12/03 EOLO Eco kW
15
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Electrical circuit.
The EOLO Eco kW electrical circuit is totally interlocked
to a microprocessor-controlled p.c.b. that controls generator
functions.
230 V AC circuit.
Safety devices and controls.
Some of the control and safety devices operate at mains
voltage (230 Vac) while the others at low voltage.
Legend:
A5 - CAR interface board
B1 - Delivery probe
B2 - D.h.w. probe
B4 - External probe (optional)
CAR- Remote control (optional)
CZ - Zone control unit (optional)
E1 - Ignition electrode
is detects ignition of the burner by whose ame it is covered.
It is connected to the integrated board.
Detection electrode
(E2)
ey interrupt power to the circuit when power input is over
3.15 A.
ey are tted on the integrated board.
Line fuse (F1)
Neutral fuse (F2)
Fuse
3,15 AF 250 V












E2 - Detection electrode
E4 - Overheating safety thermostat
F1 - Line fuse
F2 - Neutral fuse
M1 - Circulator
M20- Fan
M30- Moterized 3-way diverter valve
P1 - Central heating timer (optional)
R5 - D.h.w. temperature trimmer
R6 - Central heating temperature trimmer
R10 - Main selector switch
S4 - D.h.w. ow switch
S5 - System pressure switch
S6 - Flue pressure switch
S8 - Gas type selector switch
S20 - Room thermostat (optional)
T1 - Ignition transformer
X40 - Room thermostat jumper
Y1 - Gas valve
Y2 - Gas valve modulation coil

16
STEEkW ed 12/03 EOLO Eco kW
17
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Loads.
e board is always powered, regardless of the position of the main selector switch (R10)
(see integrated board operation).
Integrated board
It is powered by the integrated board following a d.h.w., central heating or antifreeze
request.
It permits water circulation in the primary circuit.
Boiler circulator
(M1)
It is powered at mains voltage by the integrated board when burner ignition is neces-
sary.
It allows passage of gas to the burner.
Gas valve (Y1)
(main coils)
It is controlled by the integrated board’s ignition circuit that produces an electric discharge
between its end and the earthed electrode (dummy).
Upon contact the air-gas mixture ignites.
Ignition electrode
(E1)
is ensures the ow of air inside the sealed chamber and the extraction of ue produced
by combustion.
It is powered by the integrated board.
Fan
(M20)
Low voltage circuit.
It permits operation of the boiler with 3 zone valves or external
pumps controlled by the relevant room thermostats.
Zone 1 is controlled (times and temperatures) by the CAR.
Zone control unit (CZ)
(external optional)
It permits the remote control of the generator (SUMMER/WINTER
switch, temperature setting and indication, alarms display, reset, etc.)
and acts as a weekly timer-thermostat.
Remote Control
(CAR) (optional)
See Remote Con-
trol operation
(CAR)
See zone control
unit operation
After running domestic hot water, it acts on the integrated board
that starts the d.h.w. phase.
When idle it enables operation in the central heating phase.
D.h.w. ow switch
(S4)
Interrupted
contact
It diverts the primary circuit water ow from the central heating system to the d.h.w. plate
exchanger and vice versa.
It is powered by the integrated board.
3-way diverter valve
(M30)
Safety devices and controls.
When the pressure in the boiler circuit is less than 0.3 bar it turns
the burner out.
System pressure switch
(S5)
Interrupted
contact
It is a clock that acts on a switch (see the low voltage circuit controls and safety devices) enabling
or preventing boiler operation in the central heating phase during preset time intervals.
If the timer is connected it is always powered regardless of the position of the main selec-
tor switch (R10).
Central heating timer (P1)
(External optional)

16
STEEkW ed 12/03 EOLO Eco kW
17
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Depending on the position it allows:
= With the circuit powered, the antifreeze and antilock
functions remain active, the various post-circulation and post-
ventilation functions are terminated.
( ) = Domestic hot water function and CAR (optional).
( ) = Domestic hot water and central heating function.
RESET = Reset after an ignition failure or if the overheating safety
device triggers, it allows the chimney sweep function to be activated,
it allows access to boiler parameter setting.
Main selector switch (R10) Trimmer
If the safety temperature is exceeded (105 °C) the burner switches
o.
It is positioned on the main exchanger outlet.
Safety thermostat
(E4)
Clicson
thermostat with
normally closed
contact
It lets the integrated board detect the temperature of the primary
circuit delivery water.
If it breaks, burner operation stops in both the central heating and
domestic hot water mode.
It is positioned on the main exchanger outlet.
Delivery NTC probe
(B1)
NTC probe
10 kohm 25 °C
Allows the electronic control board to read the outlet temperature
of the domestic hot water.
e sensor fault is signalled by the ashing of Led 10 ( ), the
boiler keeps working in d.h.w. mode.
It is mounted on the d.h.w. outlet body connected to the d.h.w.
plate exchanger.
D.h.w. NTC probe
(B2)
NTC probe
10 kohm 25 °C
It is powered by the integrated board with a variable d.c.
With this the pressure of the gas to the burner can be varied.
Gas valve modulator
(Y2)
Loads.
It acts on the integrated board and enables boiler operation when
the ue are extracted correctly.
If it is closed with the fan o it does not enable start of the igni-
tion cycle.
Flue pressure switch
(S6)
Switching
contact
It detects the external temperature and lets the board change
system delivery temperature according to it.
External probe
(B4) (optional)
PTC probe
1 kohm 25 °C
It acts on the integrated board enabling operation of the boiler in
the central heating phase at the selected times.
If it is mounted alone, connection is to terminals 40 and 41 of the
X14 connector after having removed jumper X40.
If it is mounted together with a room thermostat (S20) it is
connected to terminals 8 and 41 of the X14 connector after
having removed jumper X40.
Central heating timer (P1)
(external optional)
Interrupted
contact
It enables operation in the central heating phase when room
temperature is below that requested.
If the CAR device is installed, the room thermostat must be
disconnected without re-establishing the existing jumper X40.
Room thermostat (S20)
(external optional)
Interrupted
contact

18
STEEkW ed 12/03 EOLO Eco kW
19
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Electrical circuit.
Central heating phase.
Operating with a room thermostat.
e central heating phase is enabled when the main selector
switch (R10) is on “WINTER”.
When the room thermostat contact is closed (S20), the inte-
grated board powers the boiler circulator (M1) by means of
relay K3 and, by deviating the contact of relay K1, powers the
motor (M) of the 3-way diverter valve (M30) that continues
working until limit switch “1” opens when the central heating
position is reached.
In the meantime, if the ue pressure switch (S6) contact is
idle, “NC”, the adjustment circuit powers the fan (M20) by
means of relay K4.
If the contact of the system pressure switch (S5) is closed (the
pressure measured in the primary circuit is higher than the mi-
nimum value), with the enable of the safety thermostat (E4)
and consequent switching over of the ue pressure switch to
“NO” (S6), the board provide to supply the coil of K2 request
relay.
If the temperature measured by the delivery NTC probe (B1) is
below the temperature set on the control panel with the central
heating temperature trimmer, the integrated board energizes the
K2 request relay which closes the 2 contacts allowing to start
of the ignition cycle, rst controlling the ignition electrode (E1)
and then both the gas valve coils (Y1).
Burner ignition is detected by the integrated board by way of
the ionisation electrode (E2).
Operating with the remote control.
e remote control (CAR) is enabled when the main selector
switch (R10) is on “SUMMER and CAR”.
If the conditions found by the remote control (CAR) require
ignition in the central heating phase (SUM/WIN selector of the
CAR on WINTER, central heating temperature setting higher
than what the heating probe (B1) detects, request for the hourly
programmer, room temperature setting higher than the temperature
measured), the integrated board powers the boiler circulator
(M1) by means of relay K3 and burner ignition occurs as
described above.
NOTE: Each time the control unit switches o when the set
temperature is reached, the integrated board stops burner
operation in the central heating phase for the length of time set
with the board parameters (see integrated board operation).
LOW
VOLTAGE
HIGH
VOLTAGE
RELAY BOARD
SUPPLY
RELAY BOARD
CONTROL
CONTROLS-LOGIC MICROPROCESSOR
ZONE CONTROL UNIT
central heating
d.h.w.

18
STEEkW ed 12/03 EOLO Eco kW
19
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Electrical circuit.
Domestic hot water phase.
Operation.
e domestic hot water phase is enabled when the main selector
switch (R10) is on “SUMMER” or “WINTER”.
By running o some domestic hot water, the contact of the
d.h.w. ow switch (S4) closes and, if the temperature measured
by the d.h.w. NTC probe (B2) is less than the temperature
set on the control panel (or on the CAR if mounted), the inte-
grated board powers the boiler circulator (M1) by means of
relay K3 and, by deviating the contact of relay K1, powers the
motor (M) of the 3-way diverter valve (M30) that continues
working until limit switch “3” opens when the d.h.w. position
is reached.
In the meantime, if the ue pressure switch (S6) contact is
idle, “NC”, the adjustment circuit powers the fan (M20) by
means of relay K4.
If the contact of the system pressure switch (S5) is closed (the
pressure measured in the primary circuit is higher than the mini-
mum value), with the enable of the safety thermostat (E4) and
consequent switching over of the ue pressure switch to “NO”
(S6), the board closes the contact of the request relay K2, so
the ignition cycle can be started, rst controlling the ignition
electrode (E1) and then both gas valve coils (Y1).
Burner ignition is detected by the integrated board by way of
the ionisation electrode (E2).
LOW
VOLTAGE
HIGH
VOLTAGE
RELAY BOARD
SUPPLY
RELAY BOARD
CONTROL
CONTROLS-LOGIC MICROPROCESSOR
ZONE CONTROL UNIT
central heating
d.h.w.

20
STEEkW ed 12/03 EOLO Eco kW
21
STEEkW ed 12/03 EOLO Eco kW
Technical DocumentationTechnical Documentation
Technical Documentation Technical Documentation
Integrated board.
Inside the boiler’s panel there is an integrated microprocessor
controlled board that controls the appliance’s electrical devices
for the linear modulation of burner output and, by means of
LEDs, it shows the operating status of the appliance, signalling
if any of its safety devices have triggered.
e integrated board is the same on all models, both na-
tural draught and sealed chamber (NIKE/EOLO Maior
kW, EOLO Eco kW), the recognition of dierent models
is automatically done by the board through the electrical
connections.
e integrated board is always powered regardless of the posi-
tion of the main selector switch (R10).
Operation.
Central heating request.
e central heating phase is enabled when the main selector
switch (R10) is on “WINTER”.
When the room thermostat contact is closed (S20), the inte-
grated board powers the boiler circulator (M1) by means of
relay K3 and, by deviating the contact of relay K1, powers the
motor (M) of the 3-way diverter valve (M30) that continues
working until the limit switch “1” opens when the central
heating position is reached.
In the meantime, if the ue pressure switch (S6) contact is
idle, “NC”, the adjustment circuit powers the fan (M20) by
means of relay K4.
If the contact of the system pressure switch (S5) is closed (the
pressure measured in the primary circuit is higher than the mi-
nimum value), with the enable of the safety thermostat (E4)
and the consequent switching over of the ue pressure switch
to “NO” (S6), the board provide to supply the coil of K2
request relay.
If the temperature measured by the delivery probe (B1) is be-
low the temperature set on the control panel with the central
heating temperature trimmer, the integrated board energizes
the K2 request relay which closes the 2 contacts allowing to
start of the ignition cycle.
During the rst few seconds from when the gas valve (Y1) was
powered, the current to the modulation coil (Y2) is limited to
the predened slow ignition current.
Subsequently, the burner goes to the minimum pressure value
set with the “Minimum central heating power*”parameter and
after it reaches the maximum pressure value set with the “Ma-
ximum central heating power*” parameter in a time xed by
the “Central heating timer ramp*” parameter.
After this, the signal is varied in a way directly proportionate
to the dierence between the temperature set with the central
heating temperature trimmer (R6) and the temperature mea-
sured with the delivery probe (B1).
When the set temperature is exceeded (+5 °C), the contact
of relay K2 opens and the burner switches o. Re-ignition
time depends on the setting of the “Central heating ignition
timer*” parameter.
Each time the burner is switched o the fan continues working
for 30 seconds.
FUSES
MAIN SELECTOR SWITCH
TRANSFORMER
NAT-LPG
D.H.W.
CENTRAL
HEATING