1. No category

Compact wall-hung, room sealed
boiler with storage tank
S.C HABITAT & SERVICE INSTALATII S.R.L
str. Biharia nr.67-77, sector 1, Bucuresti, ROMANIA
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Tel.: 0729 983 578
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ZEUS Mini
ZEUS
Mini
Disp.Non-Stop: 0729.983.578
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Technical documentation
Technical documentation
ZEUS Mini
Compact, wall-mounted, room sealed
fan assisted boiler with storage tank
ZEUS Mini
- GENERAL CHARACTERISTICS
ZEUS Mini is a wall-mounted, sealed chamber boiler equipped with a STAINLESS STEEL storage tank
(AISI 316 L) with a useful capacity of 45 l.
The boiler has a useful rated power of 20.000 kcal/h (23.3 kW) and is very compact (H=870 mm,
L=580 mm, W=380 mm).
An electronic microprocessor P.C.B. with two LEDs to display the boiler’s operating condition carries
out adjustments and control operations (boiler ignition, temperature regulation, flame modulation, antifreeze – 5 ºC). The P.C.B. also performs diagnostics during malfunctions.
The hydraulic circuit is equipped with a copper water-gas exchanger and an electric 3-way valve that,
when required, circulates boiler water in the heating plant or in the cylinder coil to produce hot water for
the domestic circuit.
A fan is used to feed combustion air inside the airtight chamber and to exhaust the flue gases. A
differential pressure switch is used to control fan operation.
- MAIN DIMENSIONS AND CONNECTIONS
DIMENSIONS (mm)
HEIGHT
WIDTH
DEPTH
890
580
380
CONNECTIONS
GAS
G
1/2 “
PLANT
R
3/4 “
M
3/4 “
DOMESTIC
WATER
U
1/2 “
E
1/2 “
V - electric connection
G - gas supply
R - system return
M - system delivery
S - recirculation (optional )
U - domestic hot water outlet
E - domestic cold water inlet
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MAIN COMPONENTS
1 – Negative signal pressure connector
2 – Positive signal pressure connector
3 – Collection traps (A=air) (F=flue gas)
4 – Fan safety pressure switch
5 – Heating setting and limit NTC probe
6 – High temp. safety thermostat
7 – Primary exchanger
8 – Ignition and detection electrodes
9 – Combustion chamber
10– Burner
11– Automatic air vent
12– Circulator
13– Gas valve
14– Motorised three-way valve
15– System filler valve
16– Expansion tank
17– Domestic circuit NTC probe
18–316L stainless steel storage tank
19– 3 bar safety valve
20– Storage tank drain valve
21– Flue gas exhaust fan
22– Room sealed
23– Flue gas hood
24– 8 bar safety valve (dom. circuit)
25– System drain valve
CONTROL PANEL
1 – Burner operation signal - yellow
2 – Boiler block signal - red
3 – 0/SUMMER/WINTER/RESET switch
4 – Domestic circuit water temperature selector
5 – Heating temperature selector
6 – Boiler temperature pressure gauge
7 – Programmer clock hole plate
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HYDRAULIC CIRCUIT
1 – Gas valve
2 – Storage tank stainless steel coil
3 – Magnesium anode
4 – Storage tank
5 – Circulator
6 – Burner
7 – Combustion chamber
8 – Primary heat exchanger
9 – Flue gas hood
10 – Flue gas pressure switch
11 – Flue gas exhaust fan
12 – Room sealed
13 - Heating setting and limit NTC probe
14 – Over heat safety thermostat
15 – Air bleeder valve
16 – Expansion tank
17 – Plant drain valve
18 – Motorised 3-way valve
19 – 3 bar safety valve
20 – Filler valve
21 – Domestic circuit NTC probe
22 – 8 bar safety valve
23 – One-way valve
24 – Storage tank drain valve
G – Gas supply
U – Domestic hot water outlet
E – Domestic cold water inlet
R – System return
M – System delivery
The hot water for the heating system and for the domestic circuit is produced by a primary circuit and a
secondary (domestic) circuit that are activated on demand.
PRIMARY CIRCUIT (BOILER CIRCUIT)
The primary circuit with the relative control and safety devices is activated with each heating or
domestic circuit demand for water.
- OPERATION
The copper blades of the water-gas exchanger (8) absorb the heat contained in the flue gas produced by
combustion. Those blades then transfer the heat to the water being circulated inside by the boiler pump
(5).
The water is introduced directly into the plant or can be deviated inside the cylinder coil (2).
This depends on the position of the electric 3-way valve (18) which, depending on the demand, allows
water to flow through the plant delivery (M) and return (R) pipes or deviates it to the coil (2).
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- CIRCULATOR
This operates on the primary circuit return and is
physically mounted on the brass monoblock of the
electric three-way valve.
It is connected to the monoblock and to the primary
exchanger by threaded fittings.
The body is equipped with a threaded fitting to which
the automatic breather valve is connected (1).
- PUMP HEAD FLOW RATE GRAPH
The trend of the curve that represents the ratio between the flow rate and the available head will vary
depending on the pump operating speed and on whether or not the plant by-pass is activated (optional).
The curves illustrated in the graph below refer to:
- A = Circulator at maximum speed
- B = Circulator at second speed
- C = Circulator at maximum speed with by-pass (optional) activated
- D = Circulator at second speed with by-pass (optional) activated
- 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).
It consists of four pipes connected in series (1).
Because of its dimensions and characteristics, it can
also be used on EOLO Mini boiler but the hole in
which the NTC probe is inserted NTC (6) must be
closed.
It is connected to the pump delivery (return) and to the
primary circuit delivery (delivery) using slip-in pipes
(3) with an O-ring (5) that are secured by special forkshaped fasteners (4).
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- SAFETY DEVICES AND CONTROLS
System by-pass (1) (optional)
It ensures that water circulates in the primary
circuit (between delivery and return) even when
inhibited by the high resistance of the plant.
It is mounted between the plant delivery and
return connection pipes.
System filler valve (4)
This valve installed between the boiler circuit
and the domestic circuit cold water inlet is used
to pressurise the heating plant.
Its seat is located in the lower part of the threeway monoblock valve (3) where it is screwed on.
System drain valve (5)
This brass plug supplied with a hose fitting is
mounted (screwed on) to the lower part of the
three-way monoblock.
It can be loosened to drain water from the
primary circuit.
Automatic air vent (6)
This automatically expels any gaseous
substances in the boiler circuit.
It is mounted on the delivery outlet directly on
the pump casing.
3 bar safety valve (7)
This ensures that the safety pressure (3 bar) is
not exceeded in the circuit.
Attached to the delivery pipe, it expels water
through that fitting when activated.
Expansion tank (8)
It compensates for volume variations after the
water is heated and is used to limit pressure
variations.
It is located above the storage tank and has a preload pressure of 0.8 bar and a capacity of 8 l.
It is connected to the three-way monobloc by a
copper pipe (2) with threaded fittings.
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HYDRAULIC CIRCUIT
SECONDARY CIRCUIT (DOMESTIC HOT WATER CIRCUIT)
The domestic hot water circuit is involved each time the temperature of the water in the tank and
measured with the domestic NTC sensor (7) must be set to the required value.
This occurs when domestic hot water is used and to restore the losses due to thermal dispersion.
- OPERATION
When a request to enable the domestic hot water circuit is received, the P.C.B. activates the boiler pump
(1) and feeds the electric 3-way valve motor (8).
The subsequent movement of the valve to the domestic hot water circuit position (see electric 3-way
valve operation) closes the system return pipe (R) and simultaneously opens the passage to the storage
tank coil return (4).
This prevents water from circulating in the heating plant while allowing it to flow into the coil (4).
Through it walls, the coil allows the cold water to absorb the heat contained in the primary circuit water.
In this phase, the heating function is excluded and domestic water production has priority.
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- STORAGE TANK
This AISI 316L STAINLESS STEEL storage tank has a useful capacity of 45 l.
It consists of an external sleeve enclosed at the bottom by a flange (15) with inner O-Ring that can be
removed to inspect the tank (coil, anode, etc.) through the special opening.
A STAINLESS STEEL cylindrical pipe with a concentric spiral shape (coil) is inserted inside and is
coiled in the lower part of the storage tank. Heat is exchanged between the hot water in the primary
circuit and the water contained in the cylinder through the walls of the coil.
This keeps the water in the cylinder at a constant temperature and guarantees instant availability of
domestic hot water on demand (20,000 kcal/h).
The following devices ensure that it operates correctly and is maintained in good condition:
Anode (3)
It is inserted in the storage tank and protects it against
the action of galvanic currents.
It is screwed onto the external sleeve at the bottom of
the storage tank.
Polyphosphate metering unit (optional)
This prevents any limestone deposits from accumulating
on the walls of the coil.
The special kit is mounted on the domestic cold water
circuit inlet.
Recirculation Kit (optional)
This is used to connect the pipes of any recirculation
plant of the domestic hot water circuit.
It consists of a pipe that is inserted into the tank after
having removed the anode with relative plug.
When the kit is installed, the anode must be screwed to
the end of the pipe.
Domestic circuit NTC sensor (NS) (7)
This allows the printed control board to detect the
temperature of the water contained in the storage tank.
It is attached to the external wall of the storage and
inserted inside an immersion trap.
Safety valve unit (13)
This unit is located in the lower part of the cylinder near
the domestic circuit cold water inlet.
In addition to an 8-bar valve (10) that prevents the safety
pressure from being exceeded inside the storage, it also
includes:
- a filter, an 8 l/m flow limiter (12), a cylinder drain
valve with hose fitting (14) and a one-way valve (“5”
domestic circuit) to prevent a pressure increase
following heating of the domestic circuit hot water from
causing water to return toward the water mains.
Domestic hot water circuit expansion tank (11)
(optional)
It compensates for volume variations following heating
of the water contained in the cylinder.
It is connected to the safety valve unit and has a
capacity of 2 l at a pre-load pressure of 3.5 bar.
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- MOTORISED 3-WAY VALVE
This electric 3-way valve operating on the primary circuit return is used to convey cylinder water,
depending on the demand (domestic circuit or heating), into the heating plant or into the storage tank.
This depends on the position of the plug valve (3) that closes the passage to the heating system while
opening it toward the storage at the same time (domestic circuit position) or vice versa (heating
position).
The plug valve (3) moves in both positions by feeding the motor (1).
Operation
To move to the heating or domestic
circuit position, the motor (1) is
activated by the control card.
Activating the motor, whose rpm is
reduced by a special gear system,
begins rotating a disc (6) with an
eccentric connection on the shaft of that
motor.
The moving disc activates a special
coupling (5) that, with each 180°
rotation, compresses (heating position)
or releases (domestic circuit position)
the plug valve contrast spring (4).
Hydraulically reaching the requested position causes first one limit switch (2) to open and then another
to close.
This allows the voltage to be cut off to the motor, freezing it in the position reached and enabling motor
operation only when a different request (domestic circuit or heating signal) is received.
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GAS CIRCUIT
The circuit consists of an atmospheric burner and a modulating valve that are used, respectively, to burn
gas and to adjust its flow rate.
- OPERATION
Electrically feeding the main coils (3) opens both plugs inside the valve, thus allowing gas to be
conveyed to the burner.
The outlet flow rate/pressure is then adjusted using the gas valve stabiliser through the modulation coil
(1).
The fuel, through the burner nozzles (7), is injected into the Venturi tubes (gas trains) inside which the
air-gas mix is than ignited by the discharging ignition electrodes (5).
- MODULATING GAS VALVE
The gas valve (SIT 845) is equipped with two main coils (3) and a modulation coil (1) activated by the
control card.
The maximum and minimum outlet pressure calibrations are carried out on the valve (see gas settings).
Main electric coils (3)
These two ON-OFF coils are fed (230 Vac) by the control
card to ignite the burner.
They are electrically connected in parallel and fed by
mains voltage through a special connector (2).
SIT 845
Modulation coil (1)
This low-voltage coil is controlled by the modulation card.
It controls the gas valve stabiliser and can be used to vary
the outlet pressure so that it is proportional to the d.c.
signal conveyed through it.
- BURNER
The burner consists of 12 horizontal Venturi tubes into which the gas is injected by the same number of
nozzles (7) mounted on a special header (8).
Ignition occurs thanks to the control card that monitors the ignition (5) and detection (4) electrodes.
Ignition electrodes (5)
They are monitored by the control card ignition
circuit that generates an electric discharge between
the two electrodes.
They are mounted on the front of the burner between
the first and the second gas train (Venturi tube).
Detection electrode (4)
It is monitored by the control card and detects when
the burner has ignited.
It is mounted on the front of the burner on the gas
train next to the ignition electrodes (5).
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GAS SETTINGS
Maximum and minimum pressure settings are performed using the gas valve and are made considering
the values reported in the tables relative to each generator for the type of corresponding gas.
- SIT 845 VALVE
After having connected the leads of a
differential pressure gauge to the gas
valve outlet (4) and to the positive
pressure connector at the top of the
airtight chamber (see figure below), do
the following :
Maximum pressure setting
- Request some domestic circuit hot
water after having adjusted the
temperature selector to the maximum.
Turn nut “3” clockwise to increase the
pressure to the burner and counterclockwise to reduce it.
Minimum pressure setting
(to carry out after the maximum pressure
setting)
- After cutting off the power supply to
the modulation coil, turn screw “2”
clockwise to increase the pressure to the
burner and counter-clockwise to reduce
it.
1) Modulation coil
2) Min. power setting screw
3) Max. power setting screw
4) Gas valve outlet pressure connector
5) Gas valve inlet pressure connector
6) Protective cap
- GAS CONVERSION
Special kits (natural gas or LPG) are used to convert from the gas for which the boilers are designed to
operate with another type.
The conversion process entails replacing the burner nozzles and moving the “NATURAL GAS-LPG”
(JP1) bridge on the modulation card.
The maximum and minimum pressure values are then set on the gas valve as previously described.
The maximum power during heating and burner ignition pressure settings (see table below) are made
using the respective trimmers mounted on the ignition and control card (see modulation card
operation).
Soft ignition values mbar (mm H2O)
ZEUS Mini
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Natural gas
LPG
2.92 (30)
6 (60)
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FLUE CIRCUIT
- OPERATION
The combustion products, after striking the water-gas exchanger (1) are conveyed into a hood (2). The
flue gas exhauster (4) is mounted at the top of the hood.
The fan forces out the flue gases and, at the same time, creates a vacuum in the airtight chamber (5) used
to suck in air from the outside.
Correct flue gas evacuation is controlled by a differential pressure switch (3) that enables or disables
burner ignition when activated.
- AIR / FLUE GAS COLLECTION TRAPS
(6-7)
Two traps with a screw closing mechanism are
mounted externally at top of the airtight chamber.
The traps can be accessed from the front through
which it is also possible to collect samples of the
combustion air (6) and the flue gas (7).
- FLUE GAS PRESSURE SWITCH SIGNAL
PRESSURE CONNECTORS (8-9)
Two pressure connectors to measure the signal at
the ends of the flue gas pressure switch, and
equipped with a screw closing device, are mounted
externally at the top of the airtight chamber.
The positive pressure connector (9) is attached to
the inside of the airtight chamber through a silicon
tube (10).
In the same manner, the negative pressure connector
(8) is attached to a “Y” pipe (11) that is connected o
the flue gas hood (2) and to the negative pressure
connector of the flue gas pressure switch (3).
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- FLUE GAS PRESSURE SWITCH (3)
It is mounted internally at the top of the airtight chamber and, through special connectors, detects the
pressure difference between the top of the flue gas hood (point where the exhauster is located and
operates) and the interior of the airtight chamber.
The signal measured by the pressure switch varies according to the length of the suction/exhaust
terminals and can be measured by the special pressure connectors installed at the top of the airtight
chamber (8-9).
When activated, it closes a switch (SV) that affects the control card, enabling or disabling the burner
ignition.
- FAN (4)
The exhauster operates downstream from the combustion chamber and is positioned vertically at the top
of the hood (2) from which it exhausts the flue gas, conveying it into the exhaust tubes that must be
connected to the boiler.
It is activated by the control card and it operates at the same time as the burner.
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EXTRACTION AND EXHAUST SYSTEMS
(see extraction and exhaust end instructions )
ZEUS Mini is set for connecting to the special extraction and exhaust coupling pipes.
- EXHAUST
Connection to the exhaust pipes 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 pipes
system and its length (see boiler instruction booklet).
- EXTRACTION
Using the doubled system, connection to the extraction ducts is done in the same a similar way as the
exhaust pipes.
A special flange is connected to the hole with diameter 80 (2) at the top of the sealed chamber that
can be accessed after having removed the relative cap (3).
If coaxial tubes are used, suction takes place by using the concentric hole outside the exhaust fitting
(5).
- EXTRACTION - EXHAUST KIT
Coupling type horizontal concentric kit 60 / 100
(See EOLO Maior @)
Coupling type horizontal concentric kit 80 / 125
(See EOLO Maior @)
Coupling type vertical concentric kit 60 / 100
(See EOLO Maior @)
Coupling type vertical concentric kit 80 / 125
(See EOLO Maior @)
Coupling type separator kit 80 / 80
(See EOLO Maior @)
Insulated coupling type separator kit 80 / 80
(See EOLO Maior @)
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ELECTRICAL CIRCUIT
E1/E2
E3
F
IG –
JP1
JP3
LD1
- Ignition electrodes
- Detection electrode
- Fuse
- Main switch
- Gas type selector
- Heating timer
- Burner operation yellow LED
LD2 - Alarm red LED
MOD - Modulation coil
MP - Circulator
MV - Fan
NM - Delivery NTC sensor
NS - Domestic circuit NTC sensor
OP - Programmer clock
SV
TA
TS
VD
VG
- Flue gas pressure switch
- Room thermostat
- High temp. safety device
- Electric 3-way valve
- Gas valve
The ZEUS MINI electrical circuit fully interlocked with a modulating electronic card designed to control all
equipment electric devices.
Some of the control and safety devices operate at mains voltage and some at low voltage.
230 V AC CIRCUIT
SAFETY and CONTROL DEVICES
Detection electrode
(E3)
Fuse
High temp. safety device
(TS)
Detects ignition of the burner whose flame strikes it.
It is connected to the ignition/detection circuit of the control card.
It cuts off the power supply to the circuit when the absorbed current
exceeds2 A.
It is mounted on the modulation card.
Fuse
2 A 250 V
If the safety temperature is exceeded (105°C), it cuts off the power
Two-contact
supply to the main coils of the gas valve (VG).
clicson thermostat
It is located on the primary exchanger outlet.
LOADS
Circulator
(MP)
Electric 3-way valve
(VD)
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It is fed by the control card when a domestic circuit, heating or anti-freeze request is made.
It is used to circulate water in the primary circuit.
This is used to divert the flow of water in the primary circuit from the heating plant to the
cylinder coil and vice versa.
It is fed by the control card.
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Fan (MV)
Gas valve (VG)
(main coils)
Technical documentation
It conveys air inside the airtight combustion chamber and expels the flue gases produced by
combustion.
It is fed by the modulation card.
It is fed by the control card ignition circuit unit when the burner must be ignited.
It is used to convey gas to the burner.
Ignition electrodes
(E1 - E2)
They are controlled by the control card ignition circuit. It generates an electric discharge
between them that ignites the air-gas mix upon contact.
Programmer clock
(OP)
(optional)
This clock activates a switch (see low-voltage circuit safety and control devices) thus
enabling or disabling the boiler operation for heating during the selected time intervals.
It is fed by the main switch in position 0, SUMMER and WINTER.
LOW-VOLTAGE CIRCUIT
SAFETY and CONTROL DEVICES
Delivery sensor
(NM)
It allows the modulation card to detect the temperature of the delivery
water in the primary circuit.
If faulty, it blocks burner operation during heating and domestic circuit
demands.
It is located on the main exchanger outlet.
Domestic hot water circuit
sensor
(NS)
It allows the modulation card to detect the temperature of the hot water
in the cylinder.
If broken, it inhibits burner operation during the domestic hot water
circuit phase. It is inserted inside a bulb holder in contact with the
external wall of the cylinder.
10 kohm 25 º C
It acts on the control card, enabling the ignition circuit and thus burner
operation, when the fan properly exhausts the flue gases.
If closed with the fan off, the ignition cycle does not start.
Two-contact
switch
Flue gas pressure switch
(SV)
0
Main switch
(IG)
Programmer clock switch
(OP)
(optional)
Room thermostat (TA)
(optional external)
Depending on the position, the switch:
- circuit not powered
- hot water operation
- hot water and heating operation
RESET
NTC Sensor
10 kohm 25 ºC
NTC Sensor
Double switch
with 3 positions +
reset button
- 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)
This acts on the control card, enabling boiler operation during heating
at the selected time intervals.
If mounted individually, it is connected to terminals 6 and 9 of
connector M3 after having removed the pre-existing bridge P1.
If it is mounted together with a room thermostat (TA), it is connected to
terminals 6 and 7 of connector M3 after having removed the preexisting bridge P1.
Two-contact
switch
This acts on the control card, enabling boiler operation during heating
when the room temperature is less than the set value.
If mounted individually, it is connected to terminals 6 and 9 of
connector M3 after having removed the pre-existing bridge P1.
If it is mounted together with a clock (OP), it is connected to terminals
8 and 9 of connector M3 after having removed the bridge P1.
Two-contact
switch
LOADS
Modulation coil
(MOD)
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It is fed by the modulation card with a variable signal.
It is used to vary the gas pressure to the burner.
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ELECTRICAL CIRCUIT
CENTRAL HEATING PHASE
- OPERATION
The main switch (IG) is in WINTER position powers the low-voltage circuit and enables board
operation during heating.
When the room thermostat (TA) contact closes, the control circuit activates the circulator (M) by
closing the PUMP RELAY contact.
In the meantime, the resting contact of the 3-WAY RELAY supplies the motor (M) of the 3-way
valve (VD) and continues to run until the limit switch “A” opens when the heating position is
reached.
If the temperature detected by the NTC heating sensor (NM) is less than the value set on the control
panel using the heating potentiometer, the card activates the fan (MV), enabling the FAN RELAY.
When the flue gas pressure switch (SV) closes, it allows the control circuit to excite the REQUEST
RELAY.
This enables the card ignition circuit (IGNITION SECTION) that first enables the ignition
electrodes (E1-E2) and then excites the V/G RELAY.
With the consensus of the overheating thermostat (TS), the closing of the contact of RELAY V/G
powers both coils of gas valve (VG).
The ionisation electrode (E3) detects when the burner has ignited.
NOTE: Each time the control circuit shuts off once the temperature is reached, the system inhibits
burner operation during the heating phase for 180 s.
That time can be reduced to 30 s by using the special bridge (JP3) (see modulation card operation).
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ELECTRICAL CIRCUIT
DOMESTIC HOT WATER CIRCUIT PHASE
- OPERATION
The main switch (IG) in the SUMMER or WINTER position powers the low-voltage circuit and
activates the domestic hot water circuit phase operation.
If the temperature detected by the NTC heating sensor (NS) is less than the value set on the control
panel using the domestic hot water circuit potentiometer, the low-voltage circuit activates the
circulator (MP), by closing the PUMP RELAY contact.
In the meantime, the control circuit deviates the 3-WAY RELAY contact.
This supplies the motor (M) of the 3-way valve (VD) that continues to run until the limit switch “N”
opens when the domestic hot water circuit position has been reached.
Then, the control card activates the fan (MV), enabling the FAN RELAY and afterwards, following
closure of the flue gas pressure switch (SV), excites the REQUEST RELAY.
This enables the card ignition circuit (IGNITION SECTION) that first enables the ignition
electrodes (E1-E2) and then excites the V/G RELAY.
With the consensus of the overheating thermostat (TS), the closing of the contact of RELAY V/G
powers both coils of gas valve (VG).
The ionisation electrode (E3) detects when the burner has ignited.
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MODULATION CARD
The microprocessor P.C.B. installed on the ZEUS Mini includes the ignition and temperature setting
functions. It uses LEDs to specify the equipment’s operating status, indicating if any of the installed
safety devices have gripped.
Thanks to special software and an appendix specifically dedicated to the electric three-way valve control
(electric three-way valve connection module), this card is designed to be used on Mini accumulation
boilers (ZEUS Mini), instant-demand boilers (NIKE Mini and EOLO Mini) and those for heating
alone (NIKE Mini “S” and EOLO Mini “S”)
In fact, bridge JP2 can be used to select two different operating modes:
- JP2 excluded (cylinder position), the control circuit sets up to operate with an accumulation cylinder
(electric three-way valve, domestic hot water NTC probe, etc.)
- JP2 activated (instant-demand position), the control circuit sets up to operate with a hydraulic threeway valve, only one temperature probe (delivery probe) and performs the domestic hot water modulation
with a fixed set point.
NOTE: the electric connection of this P.C.B. on the Mini instantaneous versions must be made while
paying attention to connector M6.
NIKE Mini and EOLO Mini are not equipped with the domestic hot water circuit NTC probe and the
electric wiring includes a 4-pin M6 connector that should be inserted on the card’s 6-pin “M6”
connector, thus making pins 41 and 42 available (domestic hot water circuit probe).
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- OPERATION
Heating request
With the main switch (IG) in the WINTER position and the room thermostat contact (TA) closed, the
control circuit activates the circulator through the PUMP RELAY and supplies the motor (M) of the 3way valve (VD) through the 3-WAY RELAY.
If the temperature detected by the NTC heating sensor (NM) is less than the value set with the heating
potentiometer (RISC), the card supplies the fan (MV), exciting the FAN RELAY.
Once the fan starts running (MV), the flue gas pressure switch contact (SV) closes, allowing the control
circuit to excite the REQUEST RELAY.
This enables the card ignition circuit that first activates the ignition electrodes (E1-E2) and then, through
the VALVE RELAY, the main coils of the gas valve (VG).
During the ignition phase, the impulse signal sent to the modulation coil is limited by the adjustment
made with the soft ignition trimmer (IGN. POWER). Subsequently, after having detected the flame
through the ionisation electrode (E3), it returns to the minimum value set on the gas valve.
Then, the signal is varied in direct proportion to the difference between the temperature set with the
heating potentiometer (C.H.) and the one detected with the heating NTC sensor (NM). If necessary, it is
increased to reach the value adjusted with the heating maximum power trimmer (C.H. POWER) within
100 seconds.
When the set temperature value is exceeded, the REQUEST RELAY contact is opened. This
extinguishes the burner, whose ignition for the same request is inhibited for 180 s/30 s.
Domestic hot water circuit request
If the temperature detected by the NTC sensor located on the storage tank (NS) is less than the value (-7
°C) set using the domestic hot water circuit potentiometer (D.H.W.), the low-voltage circuit activates the
pump (MP) through the PUMP RELAY and supplies the motor (M) of the 3-way valve (VD) through the
resting 3-WAY RELAY NC contact.
The burner ignition process then continues in the same way as for the heating phase.
When the flame is detected using the ionisation electrode (E3), the modulation is performed in a way
that is directly proportional to the difference between the delivery temperature measured with the
domestic hot water potentiometer setting (D.H.W.) and the temperature detected by the delivery sensor
(NM).
When the temperature measured by the delivery sensor (NM) exceeds the reference delivery temperature
value, the REQUEST RELAY contact is opened, while it is closed again as soon as temperature goes
down.
When the temperature measured by the domestic hot water circuit sensor (NS) installed on the storage
tank reaches the value set with the domestic hot water circuit potentiometer (D.H.W.), the REQUEST
RELAY contact is opened and, after the post-operation time intervals, the contacts of the PUMP
RELAY and the FAN RELAY are also opened.
When the temperature goes down, the relays are powered again to begin a new ignition cycle.
During operation, if the heating sensor (NM) measures a temperature of more than 90°C, the contact of
the REQUEST RELAY is opened, while it is closed again as soon as the temperature drops below 75 ºC.
Anti-freeze request
With the main switch (IG) in the SUMMER or WINTER position, when the temperature detected by the
NTC delivery sensor (NM) drops below 4°C, the card activates the generator in the heating phase with
the burner at minimum power until the temperature in the boiler is 42 ºC.
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INPUTS
Delivery sensor
(NM)
Detection electrode
(E3)
Domestic hot water
circuit sensor
(NS)
This resistance varies in a way that is inversely proportional to the
temperature of the delivery water in the primary circuit.
It is also used as a limit thermostat (90 ºC).
NTC Sensor
10 kohm 25 ºC
This allows the card ignition circuit to detect the burner flame.
If this does not occur, the no ignition block trips and the system signals the event by lighting
LED LD 2 (red).
The eventual operation prior to burner ignition is indicated by the flashing of LED LD2 (red
This resistance varies in a way that is inversely proportional to the
temperature of the water in the cylinder.
NTC Sensor
10 kohm 25 ºC
This permits to supply the gas valve when fan operation guarantees
Flue gas pressure switch proper flue gas evacuation.
If it closes with the fan off, it does not allow the ignition cycle to start.
(SV)
Main switch
(IG)
This is a double switch that, depending on the position, may or may not
power the low-voltage circuit and indicates if operating is enabled in the
domestic hot water circuit (SUMMER) or domestic hot water circuit and
heating (WINTER) mode.
In the RESET position, it releases the ignition circuit after a flame block
or high temperature trip.
open = fan OFF
closed = fan ON
Switch A
open= circuit OFF
closed = circuit ON
Switch B
open = SUMMER
closed = WINTER
Overheat. safety
thermostat
(TS)
When the safety temperature (105 ºC) is exceeded, this device cuts off the
Two-contact
power supply to the main coils of the gas valve (VG).
When it trips it blocks boiler operation (high temperature block) and this clicson thermostat
is signalled by flashing red LED LD2.
Programmer clock
switch (OP)
(optional)
This clean-contact switch is controlled by a clock that enables or disables open = heating OFF
boiler operation during heating at the selected time intervals.
closed = heating ON
Room thermostat (TA)
(optional external)
This clean-contact switch enables the heating operating mode when the
closed = heating ON
room temperature is less than the required temperature.
open = heating OFF
OUTPUTS
Ignition electrode
(E1 - E2)
This high-voltage (about 16 kV) signal is used to feed the ignition electrodes installed on the
burner.
Modulation coil
(MOD)
This is a positive square wave signal with a variable ON-OFF ratio (duty-cycle) that controls
the gas valve modulation coil and is used to vary the gas pressure to the burner.
Programmer clock
(OP)
This is used to feed the programmer clock (optional) at 230 VAC. It can be mounted on the
boiler control panel by removing the closing plate.
The signal is present with the main switch in position 0, SUMMER and WINTER.
PUMP RELAY
This one-pole relay is designed to control the pump (MP) that is excited when it must be
utilised.
REQUEST RELAY
This one-pole relay is excited in order to ignite the burner.
The control card ignition circuit is controlled through its contact.
THREE WAY RELAY
This relay is used to feed the motor of the electric 3-way valve (VD).
It is excited with a heating request and remains at rest with a domestic hot water circuit
request.
V/G RELAY
This one-pole relay is excited by the ignition circuit to feed the main coils of the gas valve
(VG).
FAN RELAY
This one-pole relay is designed to control the fan (MV) that is excited when it must be
utilised.
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SETTINGS
Domestic hot water
potentiometer (D.H.W.)
Gas selector (JP1)
This is used to set the domestic hot water circuit temperature from 20 ºC to 55 ºC.
It adapts the gas modulation parameters that the boiler is designed to
use.
absent = natural gas
on = LPG
Heating potentiometer
(C.H.)
This is used to set the temperature of the heating water from 38ºC to 85 ºC.
Heating power trimmer
(C.H. POWER)
This is used to adjust the power during the heating phase, adapting it to the plant’s needs
(from the min. up to the max. set on the gas valve).
Heating timing (JP3)
Each time the burner turns off when the temperature is reached in the
heating phase, a delay of 3 min / 30 s is inserted up to the next
ignition for the same request.
Soft ignition trimmer
(IGN. POWER)
This is used to adjust the current to the modulation coil and thus the gas pressure to the
burner during the ignition phase (from the min.. up to 2/3 of the max. set on the valve).
Storage tank /instant.
mode selector
(JP2)
Depending on the position, it sets up the card to operate with an
absent = storage tank
electric three-way valve or with a hydraulic three-way valve.
present = instantIt is used to mount the card on Mini boilers with the storage tank
demand
(ZEUS) or instant-demand system (NIKE and EOLO).
absent = 30 s
present = 3 min
SAFETY DEVICES
Circulator anti-block
The circulator (MP) is activated for 30 seconds after 24 hours of inactivity.
During this time the three-way valve remains in the domestic hot water circuit position.
Delivery high temperature To prevent the water-gas exchanger from overheating, if the temperature of the primary
circuit detected by the heating NTC sensor (NM) exceeds 105 ºC, the fan is activated until
ventilation
the temperature drops below 100 ºC.
High temperature block
(TS)
If the high temperature thermostat contact is opened (primary circuit temperature higher than
110 ºC), boiler operation is blocked.
To restart the equipment, the main switch (IG) must be temporarily placed in the RESET
position, while making a domestic hot water circuit or heating request.
The system indicates when this safety device has tripped by flashing LED LD2 (red).
No ignition block
If within 10 seconds from the start of the ignition cycle the detection electrode (E3) does not
detect the burner flame, boiler operation is blocked.
To restart the equipment, the main switch (IG) must be temporarily placed in the RESET
position, while making a domestic hot water circuit or heating request.
The system indicates when this safety device has tripped by lighting LED LD2 (red).
No water / no circulation
To prevent the water-gas exchanger from overheating, when the heating NTC sensor (NM)
detects a temperature increase higher than 5 ºC every 1.5 seconds (no water, pump blocked,
closed plant check valves, etc.), the burner is turned off.
The system indicates when this safety device has tripped by lighting LED LD2 (red) and
flashing LED LD1 (yellow).
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NTC sensors faulty
(NM and NS)
Pump post-circulation
Technical documentation
A broken domestic hot water circuit sensor (NS) inhibits operation in the domestic hot water
circuit phase.
A broken heating sensor (NM) inhibits operation in the heating and domestic hot water
circuit phases.
The system indicates when this safety device has tripped by flashing LED LD1 (yellow).
To prevent the water-gas exchanger from overheating, at the end of each heating request the
circulator (MO) continues running for 30 seconds with the three-way valve (VD) in the
heating position.
At the end of each domestic hot water circuit request, the circulator (MP) continues running
for 30 seconds with the three-way valve (VD) in the following position:
- domestic hot water circuit, if the main switch (IG) is in the SUMMER position
(post-circulation on the cylinder coil)
- heating, if the main switch (IG) is in the WINTER position
(post-circulation on the plant)
Room sealed postventilation
After the burner is extinguished at the end of any request, the combustion chamber is emptied
by running the fan (MV) for 20 seconds.
Three-way valve antiblock
After 24 hours of inactivity the motor (M) of the three-way valve (VD) is fed for 10 seconds,
making it switch to the heating position.
SIGNALS
LD1
(yellow LED)
LD2
(red LED)
off
off
- boiler off
off
- boiler in stand-by
(waiting for requests)
ON = 1.5 s
OFF = 1.5 s
off
- broken NTC domestic hot water circuit (NS) or heating (NM)
sensor
on
off
- burner operating
off
ON = 1.5 s
OFF = 1.5 s
off
on
flashing
ON = 0.2 s
OFF = 4.5 s
Their status indicates the following:
flashing
flashing
- high temperature block trip or parasitic flame present
- no ignition block trip
flashing simultaneously
ON = 1.5 s
OFF = 1.5 s
- no flue gas pressure switch interception (SV)
flashing
ON = 1.5 s
OFF = 1.5 s
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on
- no circulation safety trip
(no water, pump blocked, etc.)
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ZEUS Mini OPERATING SEQUENCE
Heating phase
Domestic hot water phase
POWER SUPPLY
POWER SUPPLY
Main switch in WINTER position
Main switch in SUMMER or WINTER position
⇓
⇓
CONTROL CIRCUIT
POWER SUPPLY
CONTROL CIRCUIT
POWER SUPPLY
Closing the contacts of the main switch (WINTER position)
feeds the control card and enables heating phase operation
Closing the contacts of the main switch (SUMMER
position) feeds the modulating card and enables domestic
hot water circuit phase operation
⇓
⇓
CLOSING OF ROOM THERM. SWITCH
DOMESTIC HOT WATER CIRCUIT
OPERATION REQUEST
Room thermostat request
Storage water temperature lower than set value
⇓
⇓
PUMP AND 3-WAY VALVE POWER SUPPLY
PUMP AND 3-WAY VALVE POWER SUPPLY
The P.C.B. feeds the circulator and the electric three-way
valve
The valve is placed to the heating position
The P.C.B. feeds the circulator and the electric three-way
valve
The valve is placed to the domestic hot water circuit
position
⇓
⇓
IGNITION CIRCUIT POWER SUPPLY
IGNITION CIRCUIT POWER SUPPLY
If the temperature of the heating water is lower than the set
value, the card control circuit feeds the ignition circuit
The card control circuit feeds the ignition circuit
⇓
⇓
FLUE GAS PRESSURE SWITCH CONTACT CONTROL
The card checks the correct position of the flue gas pressure switch (contact open)
⇓
FAN POWER SUPPLY
The modulation card feeds the fan
⇓
FLUE GAS PRESSURE SWITCH CONTACT CONTROL
The modulation card checks that the flue gas pressure switch contact has closed following fan
operation (contact closed)
⇓
IGNITION ELECTRODE POWER SUPPLY
The card ignition circuit feeds the ignition electrodes
⇓
GAS VALVE COIL POWER SUPPLY
With the high temperature thermostat (TS) enabling signal, the ignition circuit feeds the main
coils of the gas valve.
⇓
BURNER IGNITION (SLOW)
The card sends the slow ignition signal to the modulation coil.
⇓
FLAME DETECTION
Through the ionisation electrode, the ignition unit detects the burner flame and ends the
ignition cycle
⇓
BOILER WORKING
The burner operates at a power that varies according to the type of request, the
adjustments/settings made and the temperatures detected by the NTC sensors
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ZEUS Mini TECHNICAL DATA
Nominal heat input
kW (kcal/h)
25.5 (21972)
Minimum heat input
kW (kcal/h)
11.0 (9467)
Nominal heat output (useful)
kW (kcal/h)
23.3 (20000)
Minimum heat output (useful)
kW (kcal/h)
9.3 (8000)
Useful heat efficiency at rated power
%
91.0 / 84.5
Heat losses at the casing with burner on / off
%
0.96 / 1.30
Heat losses at the chimney with burner on / off
%
0.68 / 7.70
mm
1.30
mbar (mm H2O)
20 (204)
mm
0.77
mbar (mm H2O)
29 (296)
mm
0.77
mbar (mm H2O)
37 (377)
Heating circuit maximum operating pressure
bar
3
Heating circuit maximum operating temperature
ºC
90
Heating adjustable temperature
ºC
38 - 85
Expansion vessel total volume
l
8
Expansion vessel pre-load
bar
0,8
Generator water capacity
l
3,5
Head available at a flow rate of 1000 l/h
kPa (m H2O)
23.5 (2.4)
Domestic circuit hot water production useful heat output
kW (Kcal/h)
23.3 (20000)
Domestic hot water circuit water adjustable temperature
ºC
20 - 55
Gas nozzle diameter (G20)
Supply pressure (G20)
Gas nozzle diameter (G30)
Supply pressure (G30)
Gas nozzle diameter (G31)
Supply pressure (G31)
Flow limiter
l/min
8
Domestic hot water circuit min. dynamic pressure
bar
0.1
Domestic hot water circuit max. operating pressure
bar
8
Specific D.H.W. flow rate in cont. service with ∆T 30ºC
l/min
13.9
Specific D.H.W. flow rate with ∆T 30ºC
l/min
11.1
Minimum pressure for flow limiter rated flow rate
bar
1.0
Full boiler weight
kg
95
Empty boiler weight
kg
56
Electric connection
V / Hz
230 / 50
Rated absorption
A
0.75
Installed electric power
W
135
Power absorbed by the circulator
W
67
Power absorbed by the fan
W
45
-----
IPX4D
Appliance electric plant degree of protection
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COMBUSTION PARAMETERS
(with combustion air temperature 15 ºC)
G20
G30
G31
Rated power flue gas mass flow rate
kg/h
62
62
62
Minimum power flue gas mass flow rate
kg/h
66
66
63
CO2 at rated power
%
5.85
6.88
6.7
CO2 at minimum power
%
2.26
2.6
2.7
CO at 0% O2 at rated power
ppm
93
107
91
CO at 0% O2 at minimum power
ppm
52
77
53
Nox at 0% O2 at rated power
ppm
125
344
353
Nox at 0% O2 at minimum power
ppm
86
113
199
Flue gas temperature at rated power
ºC
117
119
118
Flue gas temperature at minimum power
ºC
94
93
97
THERMAL POWER SETTINGS
NATURAL GAS (G20)
Nom. heat Nom. heat
output
output
(Kcal/h)
(kW)
Burner gas
flow rate
(m3/h)
Burner nozzle
pressure
(mbar) (mm H2O)
BUTANE (G30)
Burner gas
flow rate
(kg/h)
PROPANE (G31)
Burner nozzle
pressure
(mbar) (mm H2O)
Burner gas
flow rate
(kg/h)
Burner nozzle
pressure
(mbar) (mm H2O)
20000
23.3
2.70
11.14
114
2.01
28.30
289
1.98
36.60
373
19000
22.1
2.58
9.94
101
1.92
25.67
262
1.89
32.08
327
18000
20.9
2.45
8.83
90
1.82
23.18
236
1.80
27.96
285
17000
19.8
2.32
7.81
80
1.73
20.83
212
1.70
24.23
247
16000
18.6
2.19
6.87
70
1.63
18.62
190
1.61
20.88
213
15000
17.4
2.07
6.02
61
1.54
16.53
169
1.52
17.89
182
14000
16.3
1.94
5.24
53
1.45
14.57
149
1.42
15.26
156
13000
15.1
1.81
4.54
46
1.35
12.72
130
1.33
12.99
132
12000
14.0
1.69
3.93
40
1.26
11.00
112
1.24
11.07
113
11000
12.8
1.56
3.39
35
1.16
9.39
92
1.14
9.50
98
10000
11.6
1.43
2.92
30
1.06
7.89
81
1.05
8.30
85
9000
10.5
1.30
2.54
26
0.97
6.52
66
0.95
7.47
76
8000
9.3
1.17
2.24
23
0.87
5.20
53
0.86
7.02
72
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