Immergas EOLO Star Export User manual

EOLO Star Export
Compact wall-hung instantaneous
with sealed-room boilers
EOLO Star Export

Technical documentation Technical documentation
STES ed 07/01
1
EOLO STAR
EOLO Star
Instantaneous wall-hung room
sealed fan assisted boiler with
compact dimensions
EOLO Star
- GENERAL FEATURES
EOLO Star is a wall-hung boiler with sealed chamber and forced draught for central heating and the
production of domestic hot water.
The boiler. distinguished by compact dimensions (H=785 mm. W=450 mm. D=250 mm), has a
working power of 20.000 kcal/h (23.3 kW).
Adjustment and control of the boiler (burner ignition. temperature adjustment. flame modulation.
antifreeze up to – 5 ºC)are entrusted to an microprocessor-controlled electronic board which, by means
of two LEDs, displays boiler operation and performs diagnostics in the event of faults.
The hydraulic circuit features a bithermal type copper water-gas exchanger for the production of hot
water, an automatic system by-pass and a flow meter for tapping the hot water.
Combustion air intake inside the sealed chamber and the expulsion of gases 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
785 450 250
CONNECTIONS
GAS SYSTEM HOT WATER
GRMUE
3/4" (*)
3/4 " 3/4 " 1/2 " 1/2 "
(*) the boiler features a 90° gas cock with 3/4"
connections and φ18 mm welded connector
V - power connection
G - gas supply
U - hot water outlet
E - cold water inlet
R - system return
M - system flow

Technical documentation Technical documentation
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EOLO STAR
MAIN COMPONENT PARTS
1 - Collection traps (A=air) (F=fumes)
2 - Sealed chamber
3 - Gases expulsion fan
4 - Combustion chamber
5 – D.H.W. flow switch
6 - Gas valve
7 - Hot water NTC probe
8 - System filling cock
9 - Positive signal pressure point
10- Negative signal pressure point
11- Fan safety pressure switch
12- Heat adj. and limit NTC probe
13- Overheat. safety thermostat
14- Expansion vessel
15- Air release valve
16- Circulator
17- Absolute water pressure switch
18- Water manifold
19- 3 bar safety valve
20- System draining stopcock
21- Flue hood
22- Rapid bithermal exchanger
23- Ignition and detection electrodes
24- Burner
25- Gas cock
26- Control panel
CONTROL PANEL
1 - Boiler pressure gauge
2 - Boiler operation yellow indicator
3 - Boiler stop red indicator
4 - 0/SUMMER/WINTER/RESET switch
5 - Hot water temperature switch
6 - Central heating temp. switch
7 - Programming clock hole plate

Technical documentation Technical documentation
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EOLO STAR
HYDRAULIC CIRCUIT
1 - Hot water NTC probe
2 - Hot water flow switch
3 - Gas valve
4 - Flow limiting device
5 - System draining cock
6 - Burner
7 - Rapid bithermal exchanger
8 - Gases expulsion fan
9 - Sealed chamber
10 - Venturi
11 - Fan safety press. switch
12 - Flue hood
13 - Expansion vessel
14 - Heat adj. and limit NTC probe
15 - Overheat safety thermostat
16 - Air release valve
17 - Circulator
18 - Absolute water press. switch
19 - System bypass
20 - 3-bar safety valve
21 - System filling cock
G - Gas supply
U - Hot water outlet
E - Hot water inlet
R - System return
M - System delivery
The hot water for heating and home use is produced thanks to two separate circuits, selected
according to need.
CENTRAL HEATING CIRCUIT
The central heating circuit, with relevant control and safety devices, is operated every time a
central heating request is made.
- OPERATION
The heat contained in the gases produced by combustion is absorbed by the copper blades of the
water-gas exchanger (7) which, in turn, transfers this to the water circulating inside thanks to the
boiler pump (17).
The hot water is then transferred directly into the central heating system through the supply pipes
(M) and return pipes (R).

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EOLO STAR
- CIRCULATOR
This operates on the primary circuit return and is located
on the brass header assembly.
It is connected to the enbloc and exchanger by means of
threaded connecting pieces.
The body features a threaded connecting piece to which
is fastened the automatic outlet valve (1).
- PUMP HEAD FLOW GRAPH
The curve that represents the relation between
the flow rate and the available head depends on
the pump operating speed.
The curves shown on the graph alongside refer
to:
- A = Circulator at top speed
- B = Circulator at second speed
- BITHERMAL EXCHANGER
This is a water-gas blade exchanger of the
bithermal type with pipes and fins in
copper for the production of hot water for
central heating and home use.
It consequently works directly in both
circuits to which it is connected by pipes
with threaded connecting pieces (3) with flat
gasket seals (4).
The 6 oval pipes that make it up, inside
which flows the water of the central heating
circuit, contain an equal number of "cross"
pipes involved in direct transit of hot water
for home use (see illustration alongside).
These ducts are hydraulically connected in
parallel in groups of three on the central
heating circuit and in series in the hot water
for home use circuit.
At the exchanger exit is a 100°C
overheating safety thermostat (2) secured on
the side by means of a fork (1).
On the central heating supply pipe is a
housing where (screwed on) the relevant
NTC probe (5) is located.
EXCHANGER PIPE SECTION

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EOLO STAR
- SAFETY DEVICES AND CONTROLS
Automatic system by-pass (4)
This ensures circulation in the central heating
circuit even when this is prevented by the high
resistance of the system.
It operates between the supply and return of the
heating circuit and is accessible after unscrewing
the brass cap (5) on the side of the header (1).
System filling cock (3)
This cock is positioned between the boiler circuit
and the cold water inlet and makes it possible to
pressurise the heating system.
It is housed underneath the brass header (1) to
which it is secured.
System water pressure switch (7)
This is an absolute pressure switch that reads the
pressure inside the central heating circuit.
It is housed in the header (1) and is coupled to a
microswich that prevents boiler operation when the
read pressure is below 0.3 bar.
This way overheating of the bithermal exchanger is
prevented.
System draining cock (see “5” hydraulic circuit)
This is a brass cam featuring a hose connector
fastened (screwed) in the bottom part of the header
(1).
By loosening this, the water of the central heating
circuit can be discharged externally.
3-bar safety valve (2)
This prevents safety pressure being exceeded in the
circuit (3 bar).
This is fastened in the front part of the header (1) to
which it is fitted on the side by means of a socket-
head screw.
When this engages, water exits from the return
pipe.
Automatic air vent (8)
For automatically expelling gaseous substances in
the circuit.
Fitted to the supply pipe of the pump, directly on
the pump body.
Expansion vessel (9)
Compensates changes in volume following heating
of water and permits reducing pressure changes.
This 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 header (1) by means of
a copper pipe (6) with threaded connection pieces.

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EOLO STAR
HYDRAULIC CIRCUIT
HOT WATER CIRCUIT
- OPERATION
Running the hot water results in transit of cold water inside the flow switch (3) and consequent
closing of the electrical contact coupled to this (see electrical circuit).
As a result, the regulation circuit begins an operating stage with hot-water priority that starts the
burner and, if a central heating request is under way, switches off the boiler pump.
This way, the heat in the fumes produced by combustion is absorbed by the copper blades of the
bithermal exchanger (1) and transferred to the heating circuit water which, in turn, transfers it to the
cold water circuit inside the "cross-shaped" hot-water circuit pipes (2).
- HOT WATER FLOW SWITCH
Whenever hot water is run at a rate of at least 2.5 l/min
and with a dynamic pressure of 0.26 bar, the flow
switch (2) enables the boiler to operate in hot-water
mode.
This is done by means of a magnet which, by lifting
when invested by the cold water flow, moves near to an
electrical contact (reed relay) and causes movement by
means of a magnetic effect.

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EOLO STAR
The closing of the contact, which is positioned outside the duct through which the water flows,
enables the regulation board to start the hot-water priority operating mode.
This consists of two blocks (one made of brass and one in plastic) which are joined by a clutch and
secured by a pin (3).
At the flow switch exit is an 8l/min flow limiting device (1).
- BITHERMAL EXCHANGER (See central heating circuit)
Note. : to maintain duration and efficiency of the exchanger, the installation of the "polyphosphate
dosing kit" is recommended in the event of water whose characteristics could cause the formation of
mineral deposits (for instance, this kit is best fitted when the hardness of the water exceeds 25 French
degrees.

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EOLO STAR
GAS CIRCUIT
The circuit consists of an atmospheric burner and a modulating type valve for gas combustion and gas
flow adjustment respectively.
- OPERATION
When the main coils (3) are supplied, both inner valve shutters open, allowing the gas to flow towards
the burner.
The flow rate/outlet pressure is regulated by means of the gas valve stabiliser and the modulation coil
(1).
By means of the burner nozzles (7), the fuel is injected into the venturi pipes (ramps) inside which the
air-gas mix is obtained that is ignited by the spark from the ignition electrode (5).
- MODULATING GAS VALVE
The gas valve (SIT 845) features two main coils (3) and a modulation coil (1) controlled by the
adjustment board.
The maximum and minimum outlet pressure settings can be made on this valve (see gas adjustments).
Main electrical coils (3)
Two coils of the ON-OFF type supplied (230V AC) by
the P.C.B. when the burner has to be ignited.
These are electrically connected in parallel and
supplied by mains power through a special connector
(2).
Modulation coil (1)
This is a low-voltage coil controlled by the modulation
board.
This controls the gas valve stabiliser and permits
changing the outlet pressure in a way proportionate to
the DC signal that runs through it.
SIT 845
- BURNER
The burner consists of 12 horizontal venturi pipes (6) in which the gas is injected by an equal number of
nozzles (7) mounted on the special collector (8).
Ignition occurs by means of the adjustment board which controls the ignition electrode (5) and detection
electrode (4).
Ignition electrode (5)
This is controlled by the ignition circuit of the
adjustment board which produces an electrical charge
between its end and the burner surface that ignites the
air-gas mix.
This is positioned on the front of the burner in line
with the centre ramp.
Detection electrode (4)
This is controlled by the adjustment board and detects
burner ignition.
It is positioned on the front of the burner on the same
ramp as the ignition electrode.