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
STES ed 07/01
2
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
STES ed 07/01
3
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).

Technical documentation Technical documentation
STES ed 07/01
4
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

Technical documentation Technical documentation
STES ed 07/01
5
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.

Technical documentation Technical documentation
STES ed 07/01
6
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.

Technical documentation Technical documentation
STES ed 07/01
7
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.

Technical documentation Technical documentation
STES ed 07/01
8
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.

Technical documentation Technical documentation
STES ed 07/01
9
EOLO STAR
GAS ADJUSTMENTS
Max and minimum gas pressure adjustments can be made by means of the gas valve respecting the values
shown on the tables relating to each boiler for the type of corresponding gas.
The features of this appliance are such as to make it possible to differ minimum pressure adjustments
during operation in heating and hot water phases.
The gas valve minimum pressure adjustment does in fact correspond to the minimum pressure in hot
water phase (6,000 kcal/h) while, with regard to heating. the minimum pressure (8,000 kcal/h) can be
adjusted by means of a trimmer positioned on the modulation board (see modulation board adjustments).
- VALVE SIT 845
After connecting a differential pressure
gauge, the sockets of which must be
positioned at the outlet of the gas valve (4)
and at the positive pressure point located
in the upper part of the sealed chamber
(see illustration alongside), proceed as
follows:
Adjusting maximum pressure
- Take a sample of hot water after setting
the temperature switch at maximum.
Remove the protection cap (6) and turn nut
"3" clockwise to increase the pressure and
anticlockwise to decrease pressure.
Adjusting minimum hot water
pressure
(to be done after adjusting max pressure)
- After interrupting power to the
modulation coil, turn the red screw "2"
clockwise to increase pressure to the
burner and anticlockwise to decrease
pressure.
1) Modulation coil 4) Gas valve outlet pressure socket
2) Min power set screw 5) Gas valve inlet pressure socket
3) Max pressure adjust. nut 6) Protection cap
- CHANGING TYPE OF GAS
Adaptation to a type of gas different to that for which the boiler is intended, can be done by using the special
kits (natural gas or LPG).
The changeover consists in replacing the burner nozzles and in moving to the modulation board of the
“NATURAL GAS- LPG” (JP1).
The minimum and maximum pressures of the hot water are then set on the gas valve in the way
described above.
Adjustment of the minimum and maximum power during the heating phase can be done afterwards by
means of the respective trimmers mounted on the modulation board (see modulation board operation).
The burner ignition pressure is not adjusted because the type of board operation does not require such
setting (see modulation board operation).

Technical documentation Technical documentation
STES ed. 07/01
10
EOLO STAR
FLUE GAS CIRCUIT
- OPERATION
The products of combustion, after investing the water-gas exchanger (1), are conveyed to a hood (2) on
top of which the gas extractor (3) is fitted.
Fan operation ensures forced expulsion of the gases and, at the same time, creates a vacuum in the
sealed chamber (6) so the combustion air can be aspirated from outside.
Correct gas extraction is controlled by a special pressure switch (5), the operation of which enables or
prevents the burner from igniting.
- AIR/FLUE SAMPLING TRAPS (7-8)
In the top part of the sealed chamber are two traps
with screw closing. These are accessible from the
front and can be used to sample combustion air (7)
and gases (8).
- SIGNAL PRESSURE POINTS
FLUE PRESSURE SWITCH (9-10)
In the top outer part of the sealed chamber, two
pressure points are located. These feature screw
fastening and make it possible to measure the signal
at the ends of the flue pressure switch (5).
The negative pressure point (10) is connected to a
"Y" pipe (11) which in turn is connected to the
negative pressure point of the flue pressure switch
(5) and to the pressure point positioned at the
outlet of the venturi pipe (12) fitted in the end of
the fan exhaust.
The positive pressure point (9) is connected directly
inside the sealed chamber.

Technical documentation Technical documentation
STES ed. 07/01
11
EOLO STAR
- FLUE PRESSURE SWITCH (5)
This is positioned in the upper internal part of the sealed chamber and, by means of the special points,
detects the difference in pressure between the outlet of a special venturi pipe fitted in the fan exhaust
(negative signal) and the inside of the sealed chamber itself (positive signal).
The signal measured by the pressure switch varies according to the length of the intake/exhaust ends and
can be measured by means of the special pressure points on the top part of the sealed chamber (9-10).
When this trips, a switch (SV) is closed which controls the adjustment board and enables or prevents the
burner from igniting.
- FAN (3)
The extractor operates downstream of the combustion chamber and is physically "supported" by the top
part of the hood (2) from which is extracts the gases and conveys these into the exhaust pipes to which
the boiler is connected.
Inside the exhaust outlet, a venturi pipe (4) is fitted at the outlet of which, the negative signal of
the flue pressure switch (5) is detected.
This is controlled by the adjustment board and its operation essentially coincides with that of the burner.

Technical documentation Technical documentation
STES ed. 07/01
12
EOLO STAR
EXTRACTION AND EXHAUST SYSTEMS
(see extraction and exhaust end instructions )
EOLO Star is set for connecting to the special intake/exhaust coupling pipes.
- EXHAUST
Connection to the exhaust ducts is done by means of a flange (1)
or a curved flange to be fitted to the connector (4) on the top part
of the sealed chamber, placing in between a special shaped seal
(6).
The flange differs according to whether the doubled or
concentric system is used.
In the first case, the opening for combustion air extraction (5) is
closed while in the second case, it is exploited.
For correct boiler operation, a diaphragm (7) must be placed on
the exhaust connector (4) in between the flange used (1).
Diaphragms of different diameter are contemplated which must
be fitted according to the type of pipe and its length (see boiler
instruction booklet).
- EXTRACTION
Using the doubled system, connection to the intake ducts is done
in the same way as the exhaust pipes, connecting up to one of the
two 80 mm dia. holes (2) on the top part of the sealed chamber.
The unused hole is closed by means of one of the special caps
(3) featured on the boilers.
In the event of coaxial pipes being used, air intake takes place
by exploiting the concentric hole outside the exhaust connector
(5).
- EXTRACTION EXHAUST KIT
The kits and relevant accessories make it possible to use four concentric systems and two doubled systems.
As regards pressure drop relating to each accessory, the various possible combinations and the use of the
diaphragms to be fitted according to the length of the pipes, see the instructions concerning the extraction
and exhaust ends (boiler instruction booklet). The accessories (curves, extensions and end pieces) are of the
coupling type and seal is provided by special lip seals.
Coupling type horizontal concentric kit 60 /100
The exhaust pipe (φ60 mm) is fitted inside the extraction
pipe (φ100 mm).
Connection to the boiler is made using a 90° curve (1)
that can be positioned in any direction and which, by
means of the necessary extensions, must be connected to
the special extraction and exhaust end (2).
Max possible overall length beyond the first curve (1) is 3
straight and horizontal metres.
Coupling type horizontal concentric kit 80 /125
The exhaust pipe (φ80 mm) is fitted inside the extraction
pipe (φ125 mm).
Connection to the boiler is made using a 90° curve
diameter 60/100 (1) that can be positioned in any
direction and which, by means of the adapter 60/100-
80/125 (2) and necessary extensions, must be connected
to the special extraction and exhaust end (3).
Max possible overall length beyond the first curve (1) is
7.3 straight and horizontal metres.

Technical documentation Technical documentation
STES ed 07/01
13
EOLO STAR
Coupling type vertical concentric kit 60 /100
The exhaust pipe (φ60 mm) is fitted inside the
extraction pipe (φ100 mm).
Connection to the boiler is made using a flange (1)
that, by means of the necessary extensions, must be
connected to the special 60/100 extraction and exhaust
end with aluminium tile.
Max possible overall length is 4.7 straight and
vertical metres.
Coupling type vertical concentric kit 80 /125
The exhaust pipe (φ80 mm) is fitted inside the
extraction pipe (φ125 mm).
Connection to the boiler is made using a flange (1)
that, by means of the adapter 60/100-80/125 (3) and
necessary extensions, must be connected to the special
80/125 extraction and exhaust end with aluminium tile
(2).
Max possible overall length is 12.2 straight and
vertical metres.
80/80 coupling type separator kit
Both pipes have a diameter of 80 mm.
Connections to the boiler are made using two special
flanges for exhaust (1) from the centre pipe and
extraction (2) from one of the two side holes.
Max possible length (extraction + exhaust) is 33
straight horizontal metres and 41 straight vertical
metres.
To prevent condensation problems, the exhaust pipe
should not be more than 5 m long
Insulated 80/80 coupling type separator kit
Both pipes have a working diameter of 80 mm.
Connections to the boiler are made using two special
flanges for exhaust (1) from the centre pipe and
extraction (2) from one of the two side holes.
Insulation is obtained thanks to special seals (3)
whereby an air space can be created by means of a φ
125 mm external concentric pipe.
Max possible length (extraction + exhaust) is 33
straight metres.
To prevent condensation problems, the exhaust pipe
should not be more than 12 m long

Technical documentation Technical documentation
STES ed 07/01
14
EOLO STAR
ELECTRICAL CIRCUIT
E1 - Electrode ignition
E3 - Detection electrode
IG - Main switch
LD1 - Burner operation Led
LD2 - Signal block Led
MOD - Modulation coil
MP - Circulator
MV - Fan
NM - NTC heating probe
NS - NTC hot water probe
OP - Programmer clock
P1 - Room thermostat jumper
SP - System water pressure switch
SS - Hot water flow micro-switch
SV - Flue pressure switch
TA - Room thermostat
TS - Overheat. safety thermostat
VG - Gas valve
The electrical circuit of the EOLO STAR boiler is fully controlled by an electronic modulation board.
Some of the control and safety devices operate at mains voltage and others at low voltage.
230 V AC CIRCUIT
SAFETY DEVICES AND CONTROLS
Detection electrode
(E3) This detects ignition of the burmer by whose flame it is invested.
It is connected to the ignition/detection circuit of the adjustment board.
Fuse This interrpts power to the circuit when power input is over 2 A.
It is fitted on the modulation board. Fuse
2 A 250 V
Overheating safety device
(TS)
When the safety threshold is exceeded (105 ºC) this interrupts power to
the main coils of the gas valve (VG).
It is located at the exchanger outlet.
Double-contact
thermostat clicson

Technical documentation Technical documentation
STES ed 07/01
15
EOLO STAR
LOADS
Circulator
(MP)
This is powered by the adjustment board whenever there is a demand for heating or
antifreeze.
Permits circulation of water in the heating circuit.
Ignition electrode
(E1) This is controlled by the ignition circuit of the adjustment board which provokes an electric
spark between its end and the burner surface that ignites the air/gas mix.
Programmer clock
(OP)
(optional)
This clock operates a switch (see low-voltage circuit safety devices and controls) enabling
or disabling boiler operation during heating for the selected time intervals.
This is powered with master switch in position 0. SUMMER and WINTER.
Gas valve (VG)
(main coils)
This is powered by the ignition circuit of the adjustment board when the burner has to be
ignited.
Permits flow of gas to the burner.
Fan (MV) Ensures the flow of air inside the sealed combustion chamber and the exit of fumes
produced by combustion.
Powered by the adjustment board.
LOW-VOLTAGE CIRCUIT
SAFETY DEVICES and CONTROLS
Absolute water pressure
switch (SP) This affects the adjustment board, stopping boiler operation when the
pressure of the boiler circuit falls below 0.3 bar. Double-contact switch
C.H. NTC thermistor
(NM)
Permits the modulation board to determine the temperature of the water
supply of the heating circuit.
Any breakage will stop burner operation both during heating and hot
water phases.
It is positioned on the heating supply pipe of the exchanger.
NTC sensor
10 kohm 25 ºC
D.H.W. thermistor
(NS)
Enables the modulation board to determine hot water outlet temperature.
Its breakage stops burner operation during the hot water phase.
Fitted in the hot water pipe at exchanger outlet.
NTC sensor
10 kohm 25 ºC
Flue pressure switch
(SV)
This affects the adjustment board, enabling the ignition circuit and then
boiler operation when the fan ensures correct fume extraction.
When closed with fan off, does not enable start of ignition cycle. Double-contact
switch
Hot water switch
(SS)
Following an hot water request, this affects the adjustment board so the
boiler starts up during the hot water phase.
When idle this enables operation during the heating phase.
It is located inside the hot water flow meter.
Double-contact
switch
Depending on position, permits:
Main switch
(IG)
0
RESET
-low voltage circuit not powered
-hot water operation
- hot water and heating operation
- resets after the no ignition or high temperature safety device
have been activated (the RESET position operates at mains
voltage, closing a contact that acts on the ignition circuit)
3-position double
switch + reset
button

Technical documentation Technical documentation
STES ed 07/01
16
EOLO STAR
Programmer clock switch
(OP)
(optional)
Operates on adjustment board, enabling operation of the boiler during
heating at selected times.
If this is mounted singly, connection is made on terminals 6 and 9 of
connector M3 after removing pre-existing jumper P1.
When fitted together with an ambient thermostat (TA) it must be
connected to terminals 6 and 7 of connector M3 after removing the pre-
existing jumper P1.
Double-contact
switch
Room thermostat (TA)
(external optional)
By means of the adjustment board, this enables operation of the boiler
during heating when room temperature is below that required.
If fitted singly, connection is made to terminals 6 and 9 of connector M3
after removing the pre-existing jumper P1.
If fitted together with clock (OP) it must be connected to terminals 8 and
9 of connector M3 after removing jumper P1.
Double contact
switch
LOADS
Modulation coil
(MOD)
This is powered by the modulation board with variable continuous current.
Permits changing gas pressure to burner.

Technical documentation Technical documentation
STES ed 07/01
17
EOLO STAR
ELECTRICAL CIRCUIT
HEATING PHASE
When the main switch (IG) is in WINTER position, it powers the low-voltage circuit and enables
board operation during heating.
If the water pressure switch (SP) reads a pressure in the heating circuit above minimum value (SP
switch closed), on closing the room thermostat contact (TA), the adjustment circuit starts circulator
(MP) and powers the RELAY PUMP.
If the temperature read by the C.H. NTC sensor is below that set on the control panel by means of
the heating potentiometer, the board starts the fan (MV) by triggering the FAN RELAY.
The consequent closing of the flue gas pressure switch (SV) causes the adjustment circuit to power
the REQUEST RELAY.
This way, the board ignition circuit is enabled (IGNITION SECTION) which first of all triggers the
ignition electrode (E1) and then supplies the RELAY V/G.
With the consensus of the overheating thermostat (TS), the closing of the contact of RELAY V/G
powers both coils of gas valve (VG).
Burner ignition is detected by the ionisation electrode (E3).
NOTE: Every time the boiler shuts off after reaching the set temperature, the adjustment circuit
stops burner operation in heating phase for 180/30 seconds.

Technical documentation Technical documentation
STES ed 07/01
18
EOLO STAR
ELECTRICAL CIRCUIT
HOT WATER PHASE
Operation
When the main switch (IG) is in SUMMER or WINTER position, this powers the low-voltage
circuit and enables operation in hot water phase.
When the hot water is run, the microswitch contact (SS) of the hot water flow switch closes.
This way, if the water pressure switch (SP) measures a pressure above minimum value in the
heating circuit (SP switch closed), operation in hot water phase is enabled, during which the
circulator (MP) is not started or is switched off in the event of heating request under way.
Subsequently, if the temperature read by the NTC hot water sensor (NS) is below that set on the
control panel by means of the hot water potentiometer, the board starts the fan (MV) by triggering
the FAN RELAY.
The consequent closing of the flue pressure switch (SV) causes the adjustment circuit to power the
REQUEST RELAY.
This way, the board ignition circuit is enabled (IGNITION SECTION) which first of all triggers the
ignition electrode (E1) and then excites the RELAY V/G.
With the consensus of the overheating thermostat (TS), the closing of the RELAY V/G contact
energises both coils of the gas valve (VG).
Burner ignition is detected by the ionisation electrode (E3).