Immergas EOLO 21 Maior Guida

Technical documentation Technical documentation

STEM@ ed 06/01

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

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

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

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

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

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

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

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

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

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.

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