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

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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)

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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

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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
.

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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

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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.

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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).

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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.

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STEME ed 07/03 11 EOLO MINI
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 energised, 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.
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 electrodes (5).
- MODULATING GAS VALVE
The gas valve (Honeywell VK 4105 or SIT 845) features two main coils and a third modulation coil
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 energised (230V
AC) by the adjustment board when the burner has to
be ignited.
In the case of the SIT 845 valve, the two coils are
electrically connected in parallel, while in the case
of the Honeywell VK 4105 valve, these are
connected in series and energised by mains power
rectified through a diode jumper inside the
connection connector (2).
Modulation coil (1)
This is a low-voltage coil controlled by the
modulation circuit of the adjustment board.
This controls the gas valve stabiliser and permits
changing the outlet pressure in a way proportionate
to the signal that runs through it.
SIT 845
Honeywell VK 4105

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STEME ed 07/03 12 EOLO MINI
- BURNER
From the boiler serial number 1604235 the burner consists of 12 horizontal venturi pipes (6) (ramps
were previously 11) 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 electrodes (5) and detection
electrode (4).
Ignition electrodes (5)
These are controlled by the ignition circuit of the
adjustment board which produces an electrical
spark that ignites the air-gas mix.
They are 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
ramp alongside the ignition electrodes.

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STEME ed 7/03 13 EOLO MINI
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.
After fitting a pressure gauge, connected to
the gas valve outlet and to the positive
pressure point on the top part of the sealed
chamber (see illustration alongside),
proceed as follows:
- VALVE VK 4105 M (with yellow protection cap)
Minimum pressure adjustment
- After interrupting power to the
modulation coil, turn screw “3” clockwise
to increase pressure to the burner and
anticlockwise to decrease the pressure.
Maximum pressure adjustment
(to be done after minimum pressure
adjustment)
- Sample the d.h.w after setting the
temperature switch on maximum.
Turn nut “4” clockwise to increase the
pressure and anticlockwise to decrease the
pressure.
1) Modulation coil 5) Yellow protection cap
2) Coil pin 6) Gas valve outlet press. point
3) Min. output setscrew 7) Vale inlet press. point
4) Max output setscrew 8) Air press. point
- VALVE SIT 845
Maximum pressure adjustment
- Sample the d.h.w. after setting the
temperature switch at maximum.
Turn nut “3” clockwise to increase the
burner pressure and anticlockwise to
decrease it.
Minimum pressure adjustment
(to be done after maximum pressure
adjustment)
- After interrupting power to the
modulation coil, turn screw “2”
clockwise to increase burner pressure
and anticlockwise to decrease it.
1) Modulation coil
2) Minimum output setscrew
3) Maximum output setscrew
4) Gas valve outlet pressure point
5) Gas valve inlet pressure point
6) Protection cap

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STEME ed 07/03 14 EOLO MINI
- 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) jumper.
The minimum and maximum pressures are then set on the gas valve in the way described above.
Adjustment of the minimum and maximum output during the heating phase and of burner ignition
pressure (see table below) can be done by means of the respective trimmers mounted on the
modulation board (see modulation board operation).
Soft ignition values in mbar (mm H2O)
Natural gas LPG
EOLO Mini 5 (50) 13 (130)

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STEME ed 07/03 15 EOLO MINI
FLUE CIRCUIT
- OPERATION
The products of combustion, after investing the water-gas exchanger (1), are conveyed to a diverter (5)
on top of which the flue extractor (3) is fitted.
Fan operation ensures forced expulsion of the flue and, at the same time, creates a vacuum in the sealed
chamber (2) so the combustion air can be extracted from outside.
Correct flue extraction is controlled by a special pressure switch (4), the operation of which enables or
prevents the burner from igniting.
- AIR/FLUE SAMPLING POINTS (6-7)
In the top part of the sealed chamber are two
sumps with screw closing.
These are accessible from the front and can be used
to sample combustion air (6) and flue (7).
- SIGNAL PRESSURE POINTS
FLUE PRESSURE SWITCH (8-9)
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 (4).
The positive pressure point (8) is connected inside
the sealed chamber by means of a silicone pipe
(10).
In the same way, the negative pressure point (9) is
connected to a Y-pipe (11) which is in turn
connected to the draught diverter (5) and to the
negative pressure point of the flue pressure switch
(4).

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STEME ed. 07/03 16 EOLO MINI
- FLUE PRESSURE SWITCH (4)
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 top of the draught diverter (the point where the
extractor is positioned and operates) and the inside of the sealed chamber.
The signal measured by the pressure switch varies according to the length of the extraction/exhaust
ends and can be measured by means of the special pressure points on the top part of the sealed
chamber (8-9).
When this trips, a switch (SV) is closed which controls the adjustment board and enables or prevents
the burner from igniting.
ON OFF
Switch on and switch-off pressure - Pa (mm H2O) 61 (6,1) 47 (4,7)
- FAN (3)
The extractor operates downstream of the combustion chamber and is fastened vertically to the top
part of the diverter (5) from which it extracts the flue and conveys these into the exhaust pipes to
which the boiler is to be connected.
This is controlled by the adjustment board and its operation essentially coincides with that of the
burner.

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STEME ed. 07/03 17 EOLO MINI
EXTRACTION AND EXHAUST SYSTEMS
(see extraction and exhaust end instructions )
EOLO Mini is set for connecting to the special extraction/exhaust coupling ducts.
- 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 duct and
its length (see boiler instruction booklet).
- EXTRACTION
Using the doubled system, connection to the extraction 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, extraction takes place by exploiting the concentric hole outside the
exhaust connector (5).
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.
Coupling type vertical concentric kit 60 /100

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STTEME ed. 07/03 18 EOLO MINI
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

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STEME ed 07/03 19 EOLO MINI
ELECTRICAL CIRCUIT
E1/E2 - Ignition electrodes
E3 - Detection electrode
F - Fuse
IG - Main switch
JP1 - Gas selector
JP3 - Heating timer selector
LD1 - Flame presence yellow led
LD2 - Fault indicator red led
MOD - Modulation coil
MP - Circulating pump
MV - Fan
NM - Delivery sensor
OP - Programmer clock (timer)
P1 - Room thermostat jumper
SS - Domestic hot water switch
SV - Flue pressure switch
TA - Room thermostat
TS1 - Overheating safety device
TS2 (*) - Exchanger overheating safety
(fitted until serial number 2238340)
VG - Gas valve
The electrical circuit of the EOLO MINI boiler is fully controlled by an electronic modulation board that
controls all the electrical devices on the machine.
Depending on the type of request and the state of the safety devices, the board ignites the burner and
regulates the temperature of the d.h.w and central heating.
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 burner by whose flame it is invested.
It is connected to the ignition/detection circuit of the adjustment board.
.
Exchanger overheat. safety
(TS2)
(fitted until serial number
2238340)
When safety temperature is exceeded (115 ºC) this interrupts power to
the main coils of the gas valve (VG).
It is located at the outlet of the heat exchanger.
Two-contact
clicson thermostat
Fuse This interrupts power to the circuit when power input is over 2 A.
It is fitted on the adjustment board.
Fuse
2 A 250 V
.
Overheating safety
thermostat
(TS1)
When safety temperature is exceeded this interrupts power to the
main coils of the gas valve (VG).
Until the serial number 2238340 it was located on the delivery pipe and
was set at 100 ºC.
From serial number 2238341 it is located at the outlet of the heat
exchanger and is set at 105 ºC.
Two -contact
clicson thermostat

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STEME ed 07/03 20 EOLO MINI
LOADS
Circulating pump
(MP)
This is powered by the adjustment board whenever there is a demand for heating or
antifreeze.
Permits circulation of water in the boiler circuit.
Fan (MV) Ensures air flow inside the sealed combustion chamber and extraction of the combustion
flue.
It is powered by the adjustment board.
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.
Ignition electrodes
(E1 - E2)
These are controlled by the ignition circuit of the adjustment board which provokes an
electric spark 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 main switch in position 0. SUMMER and WINTER.
LOW-VOLTAGE CIRCUIT
SAFETY DEVICES AND CONTROLS
Delivery sensor
(NM)
This permits to the modulation board to determine the temperature of the
water supply of the primary circuit.
Any breakage will stop burner operation.
Until the serial number 2238340 it was positioned in immersion in a
sump located on the three way valve body.
From serial number 2238341 it is located at the outlet of the primary
heat exchanger .
NTC sensor
10 kohm 25 ºC
Domestic hot water switch
(SS)
Following sampling of hot water, this affects the adjustment board so the
boiler starts up during the hot water mode.
When idle this enables operation during the heating mode.
Double-contact
switch
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 ignition cycle start.
Double-contact
switch
Depending on position, permits:
Main switch
(IG)
0
(SUMMER)
(WINTER)
RESET
-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