Immergas EOLO Mini Guide

Technical documentation Technical documentation
STEME ed 07/03 1 EOLO MINI
EOLO Mini
Instantaneous wall-hung room
sealed fan assisted boiler with
compact dimensions
EOLO Mini
- GENERAL FEATURES
EOLO MINI is a wall-hung boiler for central heating and the production of domestic hot water that
stands out for its compact dimensions (773 x 450 x 250).
The boiler features a microprocessor-controlled electronic board that electronically controls burner
ignition, central heating and d.h.w. temperature and flame modulation.
The unit has a working heat output of 20.000 kcal/h (23,3 kW) and features a standard antifreeze safety
device that ensures operation with temperatures as low as –5°C.
The hydraulic circuit features a copper water-gas exchanger, a 3-way hydraulic valve and a
STAINLESS-STEEL plate exchanger for the instantaneous production of domestic hot water.
Combustion air intake inside the sealed chamber and the expulsion of flues are ensured by a fan. the
correct operation of which is controlled by a pressure switch.
- MAIN DIMENSIONS AND CONNECTIONS
DIMENSIONS (mm)
HEIGHT WIDTH DEPTH
773 450 250
CONNECTIONS
GAS HOT WATER SYSTEM
G U E R M
1/2 “ 1/2 “ 1/2 “ 3/4 “ 3/4 “
V - power connection
G - gas supply
U - domestic hot water outlet
E - domestic hot water inlet
R - system return
M - system flow

Technical documentation Technical documentation
STEME ed 07/03 2 EOLO MINI
MAIN COMPONENT PARTS
(until serial number 2238340)
1 - Flue sampling point
2 – Air sampling point
3 - Adjustment and limit NTC sensor
4 - 3-way hydraulic valve
5 - Gas valve
6 - System filling valve
7 - Positive signal pressure point
8 - Negative signal pressure point
9 - Fan safety pressure switch
10- Sealed room
11- Exchanger overheat safety (115 ºC)
12- Expansion vessel
13- Combustion chamber
14- Automatic air vent valve
15- Circulating pump
16- D.h.w. exchanger
17- 3 bar safety valve
18- System drain valve
19- Flue hood
20- Primary heat exchanger
21- Ignition and detection electrodes
22- Burner
23- Control panel
24- Fan
25- Overheat safety thermostat (100
ºC)

Technical documentation Technical documentation
STEME ed 07/03 3 EOLO MINI
MAIN COMPONENT PARTS
(from serial number 2238341)
1 - Sampling points (A=air) (F=flue)
2 - Fan
3 - 3-way hydraulic valve
4 - Gas valve
5 - System filling valve
6 - Positive signal pressure point
7 - Negative signal pressure point
8 - Fan safety pressure switch
9 - Sealed room
10- Overheat safety thermostat (105°C)
11- Adjustment and limit NTC sensor
12- Expansion vessel
13- Combustion chamber
14- Automatic air vent valve
15- Circulating pump
16- D.h.w. exchanger
17- 3 bar safety valve
18- System drain valve
19- Flue hood
20- Primary heat exchanger
21- Ignition and detection electrodes
22- Burner
23- Control panel
CONTROL PANEL
1 - Boiler thermo-pressure gauge
2 - Flame presence yellow indicator lamp
3 - Boiler block led indicator lamp
4 - 0/SUMMER/WINTER/RESET switch
5 - D.h.w. temperature selector
6 - Central heating temperature selector
7 - Programmer clock hole plate

Technical documentation Technical documentation
STEME ed 07/03 4 EOLO MINI
HYDRAULIC CIRCUIT
(until serial number 2238340)
(from serial number 2238341)
1 - System filling valve
2 - Hot water flow micro switch
3 - Gas valve
4 - 3-way hydraulic valve
5 - Adjustment and limit NTC sensor
6 - D.h.w exchanger
7 - Burner
8 - Primary exchanger
9 - Sealed room
10 - Fan
11 - Flue safety pressure switch
12 - Flue hood
13 - Overheating safety thermostat (TS1)
14 - Expansion vessel
15 - Automatic air vent valve
16 - Circulating pump
17 - Flow limiting device
18 - System drain valve
19 - 3-bar safety valve
20 - Overheat safety thermostat (TS2)
(fitted until serial number 2238340)
G - Gas supply
U - Hot water outlet
E - Hot water inlet
R - System return
M - System delivery
.

Technical documentation Technical documentation
STEME ed 07/03 5 EOLO MINI
The hot water used for central heating and the d.h.w. supply is produced by a primary circuit and a
secondary circuit (domestic hot water), which operate according to need.
PRIMARY CIRCUIT (BOILER CIRCUIT)
The primary circuit with relevant control and safety devices is started every time there is a central
heating, domestic hot water request or antifreeze request.
- OPERATION
The heat contained in the flues produced by combustion is absorbed by the copper blades of the
water-gas exchanger (8) which, in turn, transfers this to the water that circulates inside by means
of the boiler pump (16).
The hot water then directly enters the heating system through the delivery pipe (M) and return
pipe (R).
- CIRCULATOR
This operates on the primary circuit return and
is physically located on the brass return
manifold unit.
It is connected to the monobloc and primary
exchanger by means of pipes with threaded
fittings.
The casing features a threaded fitting onto
which the automatic release valve (1) is
fastened.
- HEAD FLOW GRAPH
The curve representing the system flow and
head ratio depends on the speed of pump
operation.
The curves shown on the graph alongside
refer to:
- A = Circulator at top speed
- B = Circulator at second speed
- C = Circulator at top speed with by-pass
(optional) on
- D = Circulator at second speed with
by-pass (optional) on

Technical documentation Technical documentation
STEME ed 07/03 6 EOLO MINI “S”
- PRIMARY HEAT EXCHANGER
This is a blade type water-gas exchanger consisting of four pipes connected together in series.
This is connected to pump delivery (return) and to primary circuit delivery (delivery) by means
of coupling pipes (3) featuring O.R. seals (5) secured by means of special forks (4).
(until serial number 2238340)
At the outlet.(delivery) is the overheating safety
thermostat at 115 ºC (2).
The outlet pipe features the 100 °C safety
thermostat (6) and the NTC delivery sensor (7).
(from serial number 2238341)
At the outlet.(delivery) are the overheating safety
thermostat at 105 ºC (2) and the NTC delivery
sensor (7).
On the outlet pipe is fitted anything.

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STEME ed 07/03 7 EOLO MINI
- SAFETY DEVICES AND CONTROLS
System bypass (1) (optional)
Ensures circulation of water in the primary circuit
(between delivery and return) even when the high
resistance of the system does not permit.
It is fitted between the system delivery and return
connection pipes.
System filling valve
This cock is located between the boiler circuit and
the cold d.h.w. inlet and permits pressurising the
heating system
The housing is obtained in the lower part of the
three-way valve body to which it is screwed up.
(see no. “13” 3-way valve ).
System drain valve (3)
This is a brass cap featuring a hose connector
fitted (screwed) on the bottom part of the return
manifold (2).
By loosening this, the water of the primary circuit
can be externally released.
3-bar safety valve (4)
Prevents safety pressure being exceeded in the
circuit (3 bar).
It is connected in the front part of the manifold (2)
to which it is fitted on the side by a socket screw.
Operation of this valve causes water to run out of
the return pipe.
Automatic air vent (6)
Allows automatic expulsion of any gaseous
substances in the boiler circuit.
It is fitted to the delivery pipe of the pump directly
to the body.
Expansion vessel (7)
This compensates for any changes in volume
caused by water heating and permits restricting
pressure changes.
It is positioned on the right of the boiler alongside
the sealed chamber and has a pre-load pressure of
0.8 bar and a capacity of 6 l.
It is connected to the return manifold (2) by means
of a copper pipe (5) with threaded fittings.

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STEME ed 07/03 8 EOLO MINI
HYDRAULIC CIRCUIT
SECONDARY CIRCUIT (DOMESTIC HOT WATER CIRCUIT)
- OPERATION
A d.h.w. request causes cold water to flow through the 3-way valve (1) and its subsequent movement to
operating position (see hydraulic 3-way valve operation).
This causes the delivery pipe (M) to close with simultaneous opening of the passage towards the d.h.w.
exchanger (2).
This way, circulation is prevented in the heating system, while this does occur in the plate exchanger,
inside which the d.h.w. cold water absorbs the heat contained in the primary circuit water (see d.h.w.
exchanger).
During this stage, the central heating function is disengaged and d.h.w. production has priority.
- DOMESTIC HOT WATER
EXCHANGER
This is a water-water exchanger consisting of 13
stainless-steel plates, one over the other, on the
surface of which the boiler circuit water and d.h.w.
cold water run in counter-current, and by means of
which heat exchange between the two liquids occurs.
It is fitted horizontally and is connected to the 3-way
valve (primary circuit delivery), to the hot water
outlet pipe and to the return pipe of the primary
circuit by means of threaded unions with flat seal (1).
From serial number 1511772 for NIKE Mini and from
serial number 1507922 for EOLO Mini, the hydraulic
coupling to the 3-way valve (cold water inlet) is of
the coupling type with OR seal (2), while previously
it was obtained by means of a threaded union with flat
seal.

Technical documentation Technical documentation
STEME ed 07/03 9 EOLO MINI
- 3-WAY HYDRAULIC VALVE
Whenever a domestic hot water request is made, the 3-way valve has to deviate the flow of water
of the primary circuit from the central heating system to the plate exchanger.
It is therefore connected to both the primary circuit (primary circuit delivery, system delivery
and d.h.w. exchanger delivery) and to the d.h.w. circuit (cold water inlet, plate exchanger cold
water inlet).
The component part consists of a brass structure with inside an area where the transit (supply) of
d.h.w. is detected and another area where, as a result, deviation is made to the boiler circuit.
Inside are devices that carry out this function and which, if necessary, can be replaced using the
revision kit for three-way valves in which are fitted all the component parts subject to wear
(diaphragm, rods, OR, shutter, etc).
To perform this operation, the lid (6) will have to be removed and the two parts separated that
make up the valve body after loosening the socket-head retention screws (9).
The 3-way valve assembly also features the housings for the system filling stopcock (13) and
the 8 l/min flow limiting device (8).

Technical documentation Technical documentation
STEME ed 07/03 10 EOLO MINI
Idle position (central heating)
The thrust exercised by the spring “1”
affects the diaphragm plate “4” and the
d.h.w. valve “3” fastened to rod “5”.
The valve “2” is thus kept up tight
with consequent closing of the passage
towards the d.h.w. exchanger and the
simultaneous opening towards the
system delivery pipe (M).
Following a central heating request,
pump operation causes circulation in
the system through the delivery pipe
(M) and return pipe (R).
Operating position (d.h.w.)
The flow of domestic hot water inside
the valve invests the d.h.w. valve which,
when idle, is tight up against the plate of
the perforated diaphragm “4”.
Upon transit of the water, the pressure
downstream of valve “3” is less than that
upstream (“venturi effect”).
With a flow of at least 1.5 l/min and a
dynamic water pressure of 0.3 bar, the
pressure difference between the two
points is such as to cause movement of
diaphragm “4”.
This permits pressing spring “1” and the
release of spring “11” with the
consequent movement of valve “2” and
rods “5” and “6”.
In this condition, the delivery pipe (M) is
closed while the passage towards the
plate exchanger is open.
At the same time, rod “7” positions (drops) at the point of contact of rods “5” and “6” causing the
electrical closing of the d.h.w. microswitch “8”.
At the end of the supply, the pressure difference upstream and downstream of the d.h.w. valve “3” is
cancelled out, allowing the valve to return to idle position.