Immergas EOLO Mini User manual

EOLO Mini
24-28 kW Special
Compact wall-hung
instantaneous boilers
with sealed-room
EOLO Mini 24-28 kW Special

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EOLO Mini 24-28 kW Special
Compact instantaneous wall-hung room sealed
fan-assisted boiler (type C).
EOLO Mini 24 kW Special
EOLO Mini 28 kW Special
EOLO Mini kW Special is a wall-hung room-sealed fan-assi-
sted boiler (type C) for central heating and producing domestic
hot water, characterised by its extremely compact size.
e boiler is available with an output power of 24 kW Special
(20,640 kcal/h) and 28 kW Special (24,080 kcal/h).
e boilers of the EOLO Mini kW Special series are type-
approved also for installation outside the building in a partly
sheltered location.
Note: By a partly sheltered location we mean a place where the
appliance is not exposed directly to the weather (rain, snow, hail,
etc.).
e boiler is tted with a new microprocessor controlled p.c.b.
that electronically controls burner ignition, central heating and
d.h.w. temperatures and continuous ame modulation.
With the new electronics the boiler can be connected to a
Remote Control (CAR or CRD) letting you easily control the
boiler remotely.
One of the standard features on the boiler is an antifreeze
system that protects against temperatures as low as -5°C
(optional down to -15°C).
e hydraulic circuit is equipped with a water-gas exchan-
ger in copper, a pump group made in a composite material
and a new 3-way electric valve group that allows, according
to requirements, boiler water to circulate in the central heating
system or in a STAINLESS STEEL plate exchanger for the
General features.
instant production of domestic hot water. e primary circuit
is tted with an automatic by-pass and a 3-bar safety valve.
A d.h.w. ow switch enables boiler activation if there is a
d.h.w. request.
e supply of combustion air inside the sealed chamber and
the expulsion of fumes are ensured by a fan whose correct
operation is controlled by a dierential pressure switch.
e boiler’s operating parameters are set by turning the knobs,
with the visual display of status, mode and malfunctions by
means of the LEDs on the easy-to-read display panel.

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Legend:
G - Gas supply
AC - Domestic hot water ow
AF - Domestic cold water inlet
R - C.h. return
M - C.h. ow
V - Power supply connection
EOLO Mini 24 kW Special main dimensions and connections.
EOLO Mini 28 kW Special main dimensions and connections.
Legend:
G - Gas supply
AC - Domestic hot water ow
AF - Domestic cold water inlet
R - C.h. return
M - C.h. ow
V - Power supply connection
Height (mm) Width (mm) Depth (mm)
790 450 310
Connections
GAS DOMESTIC
WATER SYSTEM
GAC AF R M
3/4” 1/2” 1/2” 3/4” 3/4”
Height (mm) Width (mm) Depth (mm)
790 450 250
Connections
GAS DOMESTIC
WATER SYSTEM
GAC AF R M
3/4” 1/2” 1/2” 3/4” 3/4”

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Legend:
1 - Sample point (A air) - (F ue)
2 - Fan
3 - D.h.w. ow switch
4 - Gas valve
5 - Filling valve
6 - Positive signal pressure point
7 - Negative signal pressure point
8 - Flue pressure switch
9 - Sealed chamber
10 - Flow probe
11 - Safety thermostat
12 - System expansion vessel
EOLO Mini 24 kW Special main components.
13 - Combustion chamber
14 - Automatic vent valve
15 - Boiler pump
16 - 3-bar safety valve
17 - D.h.w. heat exchanger
18 - 3-way valve (motorized)
19 - Automatic by-pass
20 - Draining valve
21 - Flue hood
22 - Primary heat exchanger
23 - Ignition and detection electrodes
24 - Burner
Note: Coupling system (OPTIONAL)

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Legend:
1 - Sample point (A air) - (F ue)
2 - Fan
3 - D.h.w. ow switch
4 - Gas valve
5 - Filling valve
6 - Positive signal pressure point
7 - Negative signal pressure point
8 - Flue pressure switch
9 - Sealed chamber
10 - Flow probe
11 - Safety thermostat
12 - System expansion vessel
13 - Combustion chamber
EOLO Mini 24 kW Special main components.
14 - Automatic vent valve
15 - Boiler pump
16 - 3-bar safety valve
17 - D.h.w. heat exchanger
18 - 3-way valve (motorized)
19 - Automatic by-pass
20 - Draining valve
21 - Flue hood
22 - Primary heat exchanger
23 - Ignition and detection electrodes
24 - Burner
Note: Coupling system (OPTIONAL)

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Legend:
1 - Burner operating LED
2 - D.h.w. operating LED
3 - C.h. operating LED
4 - Temperature LED - Malfunction - circulation insu-
cient
5 - Temperature LED - Malfunction - ow probe
6 - Temperature LED - Malfunction - ignition block
Control Panel.
7 - Temperature LED - Malfunction - overheating block
8 - Temperature LED - Malfunction - ue pressure switch
9 - D.h.w. stand-by selector/Remote Control - D.h.w. and C.h.-
Reset
10 - D.h.w. temperature selector
11 - C.h. temperature selector
12 - Boiler gauge

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Legend:
1 - D.h.w. ow switch
2 - Flow limiter
3 - Filling valve
4 - Gas valve
5 - Burner
6 - Primary heat exchanger
7 - Flue hood
8 - Fan
9 - Sealed chamber
10 - Flue pressure switch
11 - Flow probe
12 - Safety thermostat
13 - System expansion vessel
14 - Automatic vent valve
15 - Boiler pump
16 - D.h.w. heat exchanger
17 - 3-way valve (motorized)
18 - Automatic by-pass
19 - Draining valve
20 - 3-bar safety valve
G - Gas supply
AC - Domestic hot water ow
AF - Domestic cold water inlet
R - System return
M - System ow
Hydraulic circuit.
e primary circuit, with relevant control and safety devices,
is operated each time either a central heating or d.h.w.
request is made.
Operation.
e heat contained in the fumes produced by combustion
is absorbed by the copper blades of the water-gas primary
exchanger (6) which, in turn, transfers it to the water circula-
ting inside thanks to the boiler circulator (15).
e water is transferred directly into the system or can be
deviated to the instant stainless steel plate exchanger (16).
is depends on the position of the motorised 3-way diverter
valve (17) which, when idle allows the water to ow to the
d.h.w. exchanger (16) while if a central heating request is
made it deviates the ow to the system’s ow (M) and return
(R) pipes.
Primary circuit (Boiler Circuit).
e hot water for central heating and domestic use is produ-
ced by a primary and a secondary (d.h.w.) circuits that work
as required.

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Head ow rate graph.
e course of the curve that represents the ow rate/head ratio
available for the system depends on how fast the circulator is
working which, depending on the position, gives the system
a bigger or smaller head. e characteristic curves are shown
in the following graphs.
A = Head available to the system at third speed (with automatic by-pass)
B = Head available to the system at second speed (with automatic by-pass)
EOLO Mini 28 kW Special
EOLO Mini 24 kW Special
Head (m H2O)
Flow rate (l/h)
Head (kPa)
A
B
A
B
Head (m H2O)
Head (kPa)
Flow rate (l/h)

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Boiler circulator (1).
e pump works on the primary circuit return; it is part of the
pump body unit made in a composite material.
e automatic air vent (2) is housed directly on the body.
1
2
Primary exchanger (1).
It is a lamellar water-gas exchanger with copper tubes and ns
and at whose outlet (ow) the central heating NTC ow probe
(6) and the overtheating safety thermostat (2) are located.
e four pipes it is made of are connected in series (1).
It is connected to the circulator ow and to the primary circuit
ow by means of push-tted pipes (3) and O rings (5) and
locked with forks (4).
e exchangers of the 24 and 28 versions dier in the number
of ns (86 in the 24 version and 103 in the 28 version) and in the
dierent layout of the ow and return pipes (see drawing).
1
34
5
2
6
Flow
Return
1
34
5
2
6
Flow
Return
EOLO Mini 28 kW Special
EOLO Mini 24 kW Special

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Exchanger
ow
D.H.W.
EXCHANGER
FLOW
Motorised 3-way valve.
It is an electric motor (1) connected to the 3-way unit (2) and
locked by a fork that allows, according to the request made
(d.h.w. or central heating), boiler water to ow into the central
heating system or in the d.h.w. plate exchanger.
is depends on the position of the shutter (4) which closes
passage to the system while simultaneously opening it to the
d.h.w. exchanger (d.h.w. position) or vice versa (central heating
position).
e motor (1) is made to work by the electronic P.C.B. and,
with each 180° rotation, the shutter (4) moves into both
positions.
e hydraulic part consists of a brass unit (2).
Operation in the central heating mode.
e shutter’s (4) counteracting spring (3) is not compressed
(central heating position), keeping passage to the d.h.w. plate
exchanger closed and passage to the system ow open.
Both the spring (3) and shutter (4) are located inside the 3-
way brass body (2).
Operation in the d.h.w. mode.
e standard position of the hydraulic unit is always in the
d.h.w. mode.
e electric motor (1) pushes the rod (5) to which the shutter
(4) is connected which closes passage to the system, simulta-
neously opening it to the d.h.w. plate exchanger, the shutter’s
(4) contrasting spring (3) is compressed (d.h.w. position).
Both the spring (3) and shutter (4) are located inside the 3-way
valve brass body (2).
EXCHANGER
FLOW
SYSTEM
FLOW
1
2
3
4
5
Exchanger
return
System
ow
D.h.w. ex-
changer ow

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4
1
2
3
5
8
EOLO Mini 24 kW Special
EOLO Mini 28 kW Special
6
7
2
Safety devices and checks.
Automatic system by-pass (3).
is device guarantees the circulation of water in the central
heating circuit even when it would be prevented by the high
resistance of the system.
It works between the central heating ow and return, inserted
inside the by-pass tting (4) that connects the pump unit (2)
to the 3-way unit.
System lling unit (7).
is is a valve positioned between the boiler circuit and the
domestic cold water inlet and makes it possible to pressurise
the heating system.
is unit is connected to the d.h.w. ow switch (6) by means
of a threaded tting and to the pump unit (2) by means of
an O ring.
Automatic air vent (1).
It automatically expels gaseous substances from the boiler
circuit.
It is mounted on the circulator ow, directly on the pump
unit (2).
3-bar safety valve (5).
is valve prevents the safety pressure being exceeded in the
primary circuit (3 bar).
It tted on the front of the pump unit (2) and xed on the
outside by means of a fork.
When this valve triggers, water exits from the boiler return
pipe.
Expansion vessel (8).
It compensates for variations in volume as a result of heating
the water which also limits pressure variations.
It has a 6-litre capacity (4.5 useful litres) for the 24 model and
7.5 litres (4.5 useful litres) for the 28 model and a preload
pressure of 1.0 bar.
In the 24 model it is rectangular in shape and located on the
right-hand side of the boiler, by the side of the sealed cham-
ber while, in the 28 model it is circular in shape and located
at the rear of the boiler, behind the sealed chamber; in both
models a copper pipe connects the expansion vessel to the
pump unit (2).

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Operation.
When domestic hot water is drawn cold water ows inside
the d.h.w. ow switch (1) which closes the electrical contact
coupled to it (see the electrical circuit).
As a result, the integrated P.C.B. starts the d.h.w. priority phase
that ignites the burner and, if there’s an ongoing central heating
request, switches the 3-way diverter valve (2) moving it into the
working position (see operation of the hydraulic 3-way valve).
is causes the ow pipe (M) to close and simultaneously the
passage opens to the d.h.w. exchanger (3).
In this way circulation in the central heating system is preven-
ted while it is allowed in the plate exchanger, inside which the
domestic cold water absorbs the heat from the primary circuit
water (see d.h.w. exchanger).
So in this phase, central heating is o, domestic hot water
having priority.
e water/water heat exchange occurs inside the d.h.w. exchan-
ger (3) which is secured to the d.h.w. inlet (1) and outlet (2)
body with screws.
e top of the body on the left allows cold domestic water to
enter, while at the bottom it allows primary circuit return.
In the same way, the top part of the body on the right allows
the outlet of domestic hot water while at the bottom it allows
primary circuit ow.
Secondary circuit (D.h.w. Circuit).
Cold water
inlet
1
3
2
Primary circuit
ow
Primary
circuit return
D.h.w. outlet
D.h.w. outlet

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1
2
3
1
1
Primary
circuit
ow
Primary
circuit
return
D.h.w. ow switch (2).
Whenever domestic hot water is drawn at a rate of at least 1.5
l/min and a dynamic pressure of 0.3 bar, the ow switch (2)
enables the boiler to work in the d.h.w. mode.
is is done by means of a magnet that, lifting when hit by the
ow of domestic cold water, moves near to an electrical contact
(reed relay) causing it to move thanks to the magnetic eect.
When the contact closes, which is located outside the pipe
through which the water ows, it enables the adjustment board
to start the domestic hot water priority phase.
It consists of two parts (one in brass and one in plastic) that are
coupled together and locked with a pin.
A G1/4” thread on its body connects it to the lling unit
(3).
An 7.1 l/min (2 bar) for model 24 and a 9.2 l/min (2 bar) ow
limiter (1) for model 28 is installed at the ow switch exit.
D.h.w. exchanger.
It is a water-water exchanger made of stainless steel plates one
on top of the other - 14 (for model 24) and 16 (for model 28)
- on whose surface the boiler circuit water and the domestic
cold water ow in counter current and through which the heat
exchange takes place between the two lots of water.
e hydraulic coupling is done using four O rings (1) so it
can be connected directly to the d.h.w. inlet body and to the
d.h.w. outlet body.
D.h.w.
outlet
Cold
water
inlet
Cold
water inlet

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4
6
5
7
e circuit consists of an atmospheric burner and a modu-
lating gas valve for gas combustion and ow rate regulation
respectively.
Operation.
When the main coils (3) are energised both the inner valve
shutters open allowing gas to ow through to the burner.
e ow rate/outlet pressure is regulated by means of the gas
valve stabiliser via the modulation coil (1).
By means of the burner (7) nozzles the fuel is injected into
the horizontal Venturi tubes (ramps) inside which an optimum
air-gas mixture is obtained that is ignited by the spark of the
ignition electrode (5).
Modulating gas valve.
e gas valve (SIT 845) features two main coils (3) and a
modulation coil (1) controlled by the integrated P.C.B..
e maximum and minimum outlet pressures can be set on
this valve (see gas settings).
Main electric coils (3).
ey are two ON-OFF type coils powered (230 V AC) by the
integrated P.C.B. when the burner has to be ignited.
ey are electrically connected in parallel and supplied by
mains voltage through a connector (2).
Modulating coil (1).
is is a low voltage coil controlled by the integrated P.C.B..
It controls the gas valve stabiliser and allows the outlet pres-
sure to be varied in a way proportionate to the DC current
running through it.
Gas circuit.
Burner.
e burner consists of horizontal Venturi pipes (6) inside which
the gas is injected by the same number of nozzles (7) mounted
on the manifold (8).
e number of nozzles, whose diameter varies according to
the type of gas utilised (see technical data) are 12 (24 version)
and 14 (28 version).
Ignition occurs thanks to a p.c.b. that controls both the ignition
(5) and detection (4) electrodes.
Ignition electrodes (5).
ey are controlled by the integrated P.C.B. that produces an
electrical charge between their ends, igniting the air-gas mixture
when they come into contact.
ey are located at the front of the burner, by the centre
ramp.
Detection electrode (4).
It is controlled by the integrated P.C.B. and detects burner
ignition.
It is located on the front of the burner on the same ramp as
the right ignition electrode.
1
3
2

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Gas settings.
Maximum and minimum pressure settings are done by means
of the gas valve, observing the values given in the tables relative
to each boiler for the corresponding gas type (see technical
data).
A dierential pressure gauge is used for reading the pressure,
its positive pressure point connected to the gas valve (4) outlet
and to the positive pressure point on the ange with the holes
located at the top of the sealed chamber (see gure).
Legend:
1 - Coil
2 - Minimum output adjustment screw
3 - Maximum output adjustment nut
4 - Gas valve outlet pressure point
5 - Gas valve inlet pressure point
6 - Protection cap
SIT 845 valve
Gas valve SIT 845.
Setting maximum pressure.
Draw some domestic hot water after having put its temperature
selector on maximum.
Turn the brass nut (3) clockwise to increase pressure to the
burner and in the opposite direction to reduce it.
Setting minimum pressure
(to be done after setting maximum pressure).
After turning power o to the modulating coil, turn the screw
(2) clockwise to increase pressure to the burner and in the
opposite direction to reduce it.
Converting the gas type.
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 P.C.B..
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
P.C.B. operation).
e burner ignition pressure is not regulated because the
type of P.C.B. operation does not require such a setting (see
integrated P.C.B. operation).

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Flue circuit.
Operation.
e products of combustion, after hitting the water-gas exchan-
ger (1), are conveyed to a hood (2) on top of which the fumes
extractor (3) is tted (fan).
Fan operation guarantees the forced expulsion of the fumes
and, at the same time, creates a vacuum in the sealed chamber
(5) so the combustion air can be aspirated from outside.
Correct fume extraction is controlled by a dierential ue
pressure switch (4); when it triggers it either enables or prevents
burner ignition.
Air/fumes testing holes (7-8).
ere are two holes at the top on the outside of the sealed
chamber which can be accessed from the front; they are used
to sample combustion air (7) and fumes (8).
e two holes are closed by the one plastic cap (6).
Flue pressure switch signal pressure points (9-
10).
ere are two pressure points with screw closing at the top on
the outside of the sealed chamber. ey measure the signal at
the ends of the ue pressure switch (4).
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 (4) and to the pressure point
on the fan.
e positive pressure point (10) is connected directly to the
inside of the sealed chamber.
2
1
4
3
789
11
10
6

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Flue pressure switch (4).
It is located at the top, inside the sealed chamber and, by
means of the relative points, measures the dierence in pressure
between the fan output (negative signal) and the inside of
the sealed chamber itself (positive signal).
e signal measured by the pressure switch varies according
to the length of the aspiration/exhaust terminals and can be
measured by the relative pressure points located at the top of
the sealed chamber (9-10).
When this switch trips it causes a contact (S6) to close that
acts on the integrated P.C.B., enabling or preventing burner
ignition.
Intervention pressures
Flue pressure switch
ON
Head
(mm H2O)
OFF
Head
(mm H2O)
EOLO Mini 24-28 kW
Special 52 (5.3) 42 (4.3)
Fan (3).
e extractor works downstream from the combustion cham-
ber and is secured vertically to the top of the hood (2) from
where it extracts the fumes, conveying them to the exhaust
pipes to which the boiler is connected. It guarantees the ow
of air inside the sealed chamber at the same time.
It is controlled by the integrated P.C.B. and basically its ope-
ration coincides with that of the burner.

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B
A
1
2
3
4
Intake and outlet systems.
(see the intake and outlet terminal instructions).
e EOLO Mini kW Special boiler is designed for connecting
the couple-on air intake/outlet pipes and can be installed indo-
ors or outdoors (in a partly sheltered location) in the following
congurations:
Outdoors (in a partly sheltered location):
- room-sealed fan-assisted with direct intake (type C) using
the (optional) compulsory top cover kit;
- room-sealed fan-assisted (type C) using the vertical or hori-
zontal concentric kits, keeping the side plates and without
having to use the top cover kit.
Indoors:
- fan-assisted with open chamber (type B22) using the (optional)
compulsory top cover kit;
- room-sealed fan-assisted (type C) using the vertical or hori-
zontal concentric kits or the 80/80 Ø separator kit.
As far as concerns the pressure losses of each accessory, the
various combinations that can be created and the use of the
diaphragms to install depending on the length of the pipes see
the instructions for the air intake/outlet terminals (boiler
instruction manual).
e coupling of the accessories (curves, extensions, terminals)
is the push-tting type and sealing is ensured by silicon lip
seals.
Room-sealed fan-assisted conguration with
direct air intake (type C) for outdoor installa-
tion in a partly sheltered location (see gure on
the right).
By using the cover (1), on top of the sealed chamber, the boiler
can be installed outdoors in a partly sheltered place.
Note: in the 28 kW Special version, besides the cover (1), the
counterframe covering sheet (4) must also be mounted, xing
it to the frame with two screws.
Intake.
In order to mount the cover (1) the two plates (3) – closing the
holes at the top of the sealed chamber – have to be removed.
Combustion air is taken directly from the environment,
exploiting the gap between the bottom of the cover (1) and
the top of the boiler.
Note: in the 28 kW Special version it is compulsory to cover
the left intake hole with the plate (3).
Exhaust.
A ange (2) is used for coupling the 80 mm diameter outlet pi-
pes, used in the split systems. You can have either a horizontal
(A) or vertical (B) outlet depending on the accessories used.
To avoid condensate problems, the outlet pipe should be li-
mited to 5 straight metres for normal pipes and 12 straight
metres for insulated pipes.
Maximum permitted length is 12 straight metres.
Note: To ensure the boiler works properly with this kit it is
necessary to install a 40 Ø (EOLO 24 kW Special) or a 42.5 Ø
(EOLO 28 kW Special) diaphragm at the outlet of the sealed
chamber and before the outlet pipe (see the boiler instruction
manual).
Fan-assisted with open chamber (type B22) for
indoor installation (see gure above).
e cover kit described previously is used. By removing the
side plates from the sealed chamber, air is taken in directly
from the room where the boiler is installed.
Fumes are discharged through 80 diameter pipes in a single
ue or directly outside.

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Coupling type horizontal concentric kit Ø 60/100.
e exhaust pipe (60 mm Ø) is tted inside the aspiration
pipe (100 mm Ø).
Connection to the boiler is done using a 90° bend (2) that can
be positioned in any direction and which, by means of the
necessary extensions, is connected to the specic aspiration
and exhaust terminal (3).
e maximum overall permitted length beyond the rst bend
(2) is 3 straight horizontal metres.
Coupling type horizontal concentric kit Ø 80/125.
e exhaust pipe (80 mm Ø) is tted inside the aspiration
pipe (125 mm Ø).
Connection to the boiler is done using a 90° 60/100 Ø bend
(2) that can be positioned in any direction and which, by
means of the 60/100-80/125 adapter (3) and necessary ex-
tensions, is connected to the specic aspiration and exhaust
terminal (4).
e maximum overall permitted length beyond the rst bend
(2) is 7.3 straight horizontal metres.
1
3
2
56
4
1
3
2
45
Sealed chamber, fan-assisted conguration
(type C).
Exhaust.
Connection to the fumes exhaust pipes is through a ange (1)
or a anged curve to x to the tting (4) at the top of the sealed
chamber, placing a shaped seal in between (6).
e ange diers according to whether the system is used split
or concentric.
In the rst case, the passage for the intake of combustion air
(5) is closed while in the second case it is used.
To ensure correct operation of the boiler it is necessary to put
a diaphragm (7) on the exhaust tting, between it and the
ange used (1).
ere are dierent diameter diaphragms, mounted according
to the type of pipe and its length (see boiler instruction
booklet).
Intake.
Using the split system, connection to the intake pipes is done
in exactly the same way as for the exhaust pipes, connecting
to one of the two 80 mm Ø holes (2) at the top of the sealed
chamber.
e unused hole is closed with one of the plastic caps (3)
supplied with the boiler.
If coaxial pipes are used, the intake of combustion air is done
exploiting the concentric hole, outside the exhaust tting
(5).
Intake and Exhaust Kits.
e kits and their accessories permit use of four concentric
systems and two split systems.
As regards pressure losses relating to each accessory, the various
possible combinations and the use of the diaphragms depen-
ding on the length of the pipes used, follow the instructions
given for the intake and exhaust terminals (see the boiler
instruction booklet).
e coupling of the accessories (bends, extensions and termi-
nals) is the tted type while sealing is guaranteed by silicone
lip seals.
1
2
3
4
5
7
6