Immergas EOLO 21 Maior Guide

Technical documentation Technical documentation
STEM@ ed 06/01
1
EOLO MAIOR @
EOLO Maior @
Instantaneous wall-hung boilers
with sealed combustion chamber
fan assisted
EOLO 21 Maior @
EOLO 24 Maior @
EOLO 27 Maior @
- GENERAL FEATURES
The EOLO Maior @ series comprises sealed-chamber boilers with forced draught (fan assisted) for
central heating and the production of domestic hot water.
The range includes electronic-ignition versions with working outputs of 21,000 kcal/h (24.4 kW), 24,000
kcal/h (27.9 kW) and 27,000 kcal/h (31.4 kW).
Adjustment and control of the boiler are entrusted to a microprocessor-controlled electronic board
thanks to which the appliance can be connected to the Remote Friend Control (optional).
The hydraulic circuit features a copper water-gas exchanger, an automatic system by-pass and a new
brass monobloc to which is fitted the hydraulic 3-way valve which ensures, according to need,
circulation of boiler water in the heating system or in a stainless-steel plated exchanger for the
instantaneous production of d.h.w.
Combustion air flow into the sealed chamber and flue extraction are ensured by a fan, the correct
operation of which is controlled by a differential pressure switch.
All the models feature as standard an antifreeze safety device that protects down to temperatures
as low as -5°C.
- MAIN DIMENSIONS AND CONNECTIONS
DIMENSIONS (mm)
HEIGHT WIDTH DEPTH
EOLO 21/24/27 850 450 350
CONNECTIONS
GAS D.H.W. SYSTEM
G U ERM
EOLO 21/24/27 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
STEM@ ed 06/01
2
EOLO MAIOR @
MAIN COMPONENT PARTS
1 - Intake points(A= air) (F=flues)
2 - Fan safety pressure switch
3 - Flue extraction fan
4 - NTC probe for regulating the d.h.w.
5 - Gas valve
6 - System emptying stopcock
7 - System filling stopcock
8 - Automatic air vent
9 - Sealed chamber
10 - Expansion vessel
11- NTC limit and adjustment probe
12- Overheat. safety thermostat
13- Combustion chamber
14- Circulator
15- System water pressure switch
16- Plated exchanger
17- 3-bar safety valve
18- Automatic bypass disengage. screw
19- 3-way hydraulic valve
20- Positive signal pressure point
21- Negative signal pressure point
22- Draught diverter
23- Primary heat exchanger
24- Ignition and detection electrodes
25- Burner
CONTROL PANEL
1 - Heating temperature switch
2 - D.h.w. temperature switch
3 - Burner operating yellow indicator
4 - Green power indicator
5 - Switch 0 / Summer and CAR / Winter / Reset
6 - Boiler thermo-pressure gauge
7 – Red ignition stop indicator

Technical documentation Technical documentation
STEM@ ed 06/01
3
EOLO MAIOR @
EOLO Maior S @
Sealed combustion chamber fan
assisted boilers for central heating
only
EOLO 21 Maior S @
EOLO 24 Maior S @
- GENERAL FEATURES
The EOLO Maior "S" @ is a sealed combustion chamber boiler with forced draught (fan assisted)
for central heating only.
The range features two versions with electronic ignition with working outputs of 21,000 kcal/h (24.4
kW) and 24,000 kcal/h (27.9 kW).
Adjustment and control of the boiler are entrusted to a microprocessor-controlled electronic board
thanks to which the appliance can be connected to the Remote Friend Control (optional).
The appliances feature a copper water-gas exchanger and a standard antifreeze safety device that
protects down to temperatures as low as -5°C.
- MAIN DIMENSIONS AND CONNECTIONS
DIMENSIONS (mm)
HEIGHT WIDTH DEPTH
EOLO 21/24 S 850 450 350
CONNECTIONS
GAS D.H.W. SYSTEM
GERM
EOLO 21/24 S 1/2 “ 1/2 “ 3/4 “ 3/4 “
V - power connection
G - gas supply
E - d.h.w. inlet
R - system return
M - system supply

Technical documentation Technical documentation
STEM@ ed 06/01
4
EOLO MAIOR @
MAIN COMPONENT PARTS
1 - Intake points(A= air) (F=flues)
2 - Fan safety pressure switch
3 - Flue extraction fan
4 - Gas valve
5 - System emptying stopcock
6 - System filling stopcock
7 – Automatic air vent
8 - Sealed chamber
9 - Expansion vessel
10- NTC limit and adjustment probe
11- Overheating safety thermostat
12- Combustion chamber
13- Circulator
14- System water pressure switch
15- 3-bar safety valve
16- Positive signal pressure point
17- Negative signal pressure point
18- Draught diverter
19- Primary heat exchanger
20- Ignition and detection electrodes
21- Burner
CONTROL PANEL
1 - Heating temperature switch
2 - Red ignition stop indicator
3 - Burner operating yellow indicator
4 - Green power indicator
5 - Switch 0 / Summer and CAR / Winter / Reset
6 - Boiler thermo pressure gauge

Technical documentation Technical documentation
STEM@ ed 06/01
5
EOLO MAIOR @
HYDRAULIC CIRCUIT
EOLO Maior 21-24-27 @ EOLO Maior 21–24 S @
1- Minimum flow shutter (*)
2- Flow limiting device (*)
3- 3-way hydraulic valve (*)
4- Gas valve
5- D.h.w. exchanger (*)
6- NTC d.h.w. probe (*)
7- Burner
8- Primary exchanger
9 - Sealed chamber
10 - Flue hood
11 - Fan
12 - Fan safety pressure switch
13- Overheat. safety thermostat
14- NTC adjustment and limit
probe
15- Automatic air vent
16- Expansion vessel
17- Circulator
18- One way valve (*)
19- Automatic bypass (*)
20- Bypass disengag. screw (*)
21- 3-bar safety valve
22- System water pressure
switch
23- D.h.w. flow microswitch (*)
24- Filling stop cock
25- One way valve (**)
G - Gas supply
U - Hot water outlet (*)
E - D.h.w. inlet
R - System return
M - System delivery
(*) only on versions with d.h.w.
production
(**) only on version 27
PRIMARY CIRCUIT (BOILER CIRCUIT)
The primary circuit with relevant control and safety devices is started every time there is a central heating or
domestic hot water request.
- OPERATION
The heat contained in the combustion products is absorbed by the copper blades of the water-gas exchanger (8),
which in turn transfers this heat to the water circulating inside thanks to the boiler pump (17).
In the case of the models for central heating only (S), the water flows directly into the system, while in the case of
boilers with d.h.w. production, this can be deviated inside an instantaneous plate exchanger (5) made of
STAINLESS steel.
This depends on the position of the 3-way hydraulic valve (3), which when idle permits flow through the system
delivery pipe (M) and return pipe (R) while, following running of the d.h.w., flow is deviated towards the d.h.w.
exchanger (5).
- CIRCULATOR
This operates on the primary circuit return and is located on
the brass header assembly.
It is connected to the enbloc by means of a threaded
connecting piece, while the primary exchanger and expansion
vessel are connected by means of coupling pipes (2) with O.R.
seal (3), locked by means of special forks (1).
The pumps used differ according to boiler output (see head -
flow graph).

Technical documentation Technical documentation
STEM@ ed 06/01
6
EOLO MAIOR @
- HEAD FLOW GRAPH
The curve that represents the relation between the flow
rate and the available head depends on the pump
operating speed and on whether the system bypass is
engaged or not (optional on "S" versions)
The curves shown on the graph alongside refer to:
- A = Circulator at top speed with bypass disengaged
- B = Circulator at top speed with bypass engaged
- C = Circulator at second speed with bypass disengaged
- D = Circulator at second speed with bypass engaged
EOLO 21 Maior @
EOLO 21 Maior S @
EOLO 24 Maior @
EOLO 24 Maior S @
EOLO 27 Maior @
- PRIMARY EXCHANGER
This is a water-gas blade exchanger with pipes and fins in
copper at the outlet (delivery) of which are positioned the
NTC heating sensor (6) and the overheating safety
thermostat (2).
The size and layout of the pipes differ according to boiler
output.
In the 21 and 24 versions the four pipes making it up are
connected in series (1) while on the EOLO 27 they are
connected in parallel (7) two by two to reduce flow
resistance to the utmost and provide the greater head
required by boiler output.
It is connected to pump delivery and to primary circuit
delivery by means of coupling pipes (3) with OR seal (5)
fastened with special forks (4).

Technical documentation Technical documentation
STEM@ ed 06/01
7
EOLO MAIOR @
- SAFETY DEVICES AND CONTROLS
Automatic system by-pass (1)
(combined versions only)
This ensures circulation in the primary circuit even
when this is prevented by the high resistance of the
system.
It operates between the supply and return of the
primary circuit and is accessible after the three-way
enbloc in brass into the two sections of which it is
made.
It can be disengaged (closed) by turning the bypass
disengagement screw (2) clockwise.
In the case of models for central heating only (S), the
bypass is optional and is fitted between the system
delivery and return connection pipes.
System filling unit (5)
This stopcock is positioned between the boiler circuit
and the cold water inlet and makes it possible to
pressurise the heating system.
It is housed in the lower part of the enbloc to which it
is screwed up.
In the case of version 27 only, downstream of the
stopcock, an one way valve is fitted (6)
(disconnector) that prevents accidental flow of water
from the primary circuit to the water network (d.h.w.
circuit).
System water pressure switch (3)
This reads the pressure inside the primary circuit.
It is housed in the enbloc and is coupled to a
microswitch that prevents boiler operation when the
read pressure is below 0.3 bar.
This way overheating of the main exchanger is
prevented.
3-bar safety valve (4)
This prevents safety pressure being exceeded in the
circuit (3 bar).
It is fastened in the front part of the enbloc by means
of a socket-head screw.
When this engages, water exits from the delivery pipe.
Automatic air vent (7)
For automatically expelling any gaseous substances in
the circuit.
Fitted on the water side of the expansion vessel.
Expansion vessel (8)
Compensates changes in volume following heating of
water and permits reducing pressure changes.
This is positioned in the rear of the appliance and is
connected to the pump by means of a coupling pipe (9).
It has a pre-load pressure of 0.8 bar and a capacity of 8
l in versions 21-24 and 10 l in version 27.

Technical documentation Technical documentation
STEM@ ed 06/01
8
EOLO MAIOR @
HYDRAULIC CIRCUIT
SECONDARY CIRCUIT (D.H.W. CIRCUIT)
The models with instantaneous production feature a secondary hydraulic circuit that starts up only when
domestic hot water is run.
- OPERATION
Running the hot water results in transit of cold water inside the 3-way valve (1) and its consequent shift
to operating position (see 3-way hydraulic valve operation).
As a result, the return pipe (R) closes and the transit way is opened to the d.h.w. exchanger (2)
This way, circulation in the central heating system is prevented while this becomes possible in the plate
exchanger (2), inside which the cold water absorbs the heat in the primary circuit (see d.h.w. exchanger).
In this phase, the central heating function is disengaged and priority is given to the production of d.h.w.
- DOMESTIC HOT WATER EXCHANGER
This is a water-water exchanger consisting of
STAINLESS-steel plates placed one on top of the other
(15 in version 21 and 19 in version 24, 21 in version 27)
on the surface of which runs in counterflow the water of
the boiler circuit and the cold water for the d.h.w., and
through which the heat exchange occurs between the
two liquids.
To reduce mineral deposits to the utmost at the hot water
inlet, a single-acting valve (2) is fitted that prevents the
exchanger temperature from rising during operation in
central heating phase.
Hydraulic coupling is achieved by means of four O.R.
rings (1) for direct coupling to the 3-way enbloc to
which the exchanger is fastened.

Technical documentation Technical documentation
STEM@ ed 06/01
9
EOLO MAIOR @
- HYDRAULIC 3-WAY VALVE
Whenever there is a d.h.w. request, the valve deviates primary circuit flow from the heating system to
the plate exchanger.
The component part is an integral part of the 3-way brass enbloc and comprises an area where the transit
of d.h.w. is detected and another where, following this, deviation occurs to the boiler circuit.
The core of the valve consists of a noryl assembled sealing unit (10), which can be removed from the
enbloc after removing the cover (11) and diaphragm (1).
In the case of the Maior @series, both the assembled cartridge used during production and the pre-
assembled cartridge used as a spare are interchangeable with those fitted on previous MAIOR versions,
despite rods (8 - 9) being used with 3 mm diameter and O.R. rings in EPDM peroxide that give these
greater resistance to mechanical and chemical stress.
At the cold water inlet is a flow limiting device (5) the value of which differs according to appliance
output (8 l/min in 21e versions, 10 l/min in 24 versions and 12 l/min in 27 versions).
Idle position (central heating)
The thrust of the spring (4) keeps the shutter (3) tight
so the opening towards the d.h.w. exhanger is closed
and, at the same time, the system return pipe (R) is
opened.
Following a central heating request, pump operation
enables circulation in the system through the delivery
pipe (M) and return pipe (R).

Technical documentation Technical documentation
STEM@ ed 06/01
10
EOLO MAIOR @
- Operating position (domestic hot water)
Running the domestic hot water generates a flow
inside the valve that invests the d.h.w. valve (6).
This represents a constriction (venturi pipe)
downstream of which the pressure of the water is
lower than upstream.
With a flow of at least 1.85 l/min and a dynamic water
pressure of 0.4 bar, the pressure difference between
the two points is such as to cause the movement of the
diaphragm (1).
The movement is conveyed to the rods (8-9) and plate
(2) which first of all cause shutter (3) to move and
then the d.h.w. microswitch (7) to close with
consequent powering of the pump and modulation
board.
In this condition, the return pipe (R) is closed, while
the opening is open towards the exchanger inside
which the water of the primary circuit circulates.
When the d.h.w. supply has terminated, the pressure
difference upstream and downstream of the d.h.w.
valve (6) is cancelled out, enabling the valve to return
to idle position.