
2
Dear Customer,
Thank you for choosing an ARISTON boiler.
We guarantee that your boiler is a reliable
and technically sound product.
This User's Manual provides detailed
instructions and recommendations for proper
installation, use and maintenance.
Remember to keep this manual in a safe place
for future reference i.e. by the gas meter.
Your local MTS Servicing Centre is at your
complete disposal for all requirements.
The guarantee on this appliance is
valid for 12 months from the first
day of installation.
Repairs to the electric, hydraulic or
gas circuits may be carried out only
by your local authorised MTS
Servicing Centre.
Every attempt has been made to avoid
errors of any kind
in this User's Manual, the Management
invites customers to inform
of any inaccuracies which they may find.
This will help to improve our service

TABLE OF CONTENTS
1. GENERAL INFORMATION page 4
Technical Information page 5
Control Panel page 6
2. OPERA TING INSTRUCTIONS page 7
3. USEFUL INFORMATION AND TROUBLESHOOTING page 12
4. MAINTENANCE page 15
5. CHANGE OF GAS TYPE page 15
6. TIME CLOCK page 15
IMPORTANT!
Please read this manual carefully.
For additional information, please consult the “Installation and Servicing
Instructions.”
Make sure to keep the manuals provided with the appliance so that they can
be used by the end-user, installer or our authorised engineer.
3

4
1. GENERAL INFORMATION
MTS (GB) Limited support the
initiative. Your installer will give you, and
show you how to use, a logbook which will
give you important information about your
boiler, and heating system. Please have this
logbook to hand whenever you contact a
service engineer or us.
All CORGI Registered Installers carry a
CORGI ID card, and have a registration
number. Both should be recorded in your
boiler Logbook. Y ou can check your installer
is CORGI registered by calling CORGI direct
on :- (01256) 372300.
This is an appliance for the production of
central heating. This appliance must be used
only for the purpose for which it is designed.
The manufacturer declines all liability for
damage caused by improper or negligent use.
Do not allow children or inexperienced
persons to use the appliance without
supervision.
If you smell gas in the room, do not turn on
light switches, use the telephone or any other
object which might cause sparks.
Open doors and windows immediately to
ventilate the room.
Shut the gas mains tap (on the gas meter) or
the valve of the gas cylinder and call your Gas
Supplier immediately.
If you are going away for a long period of
time, remember to shut the mains gas tap or
the gas cylinder valve.
Before any intervention within the boiler it is
first necessary to cut off the electrical power
supply by turning the external switch to
“OFF”.

TECHNICAL INFORMATION
5
GENERAL DATA
Heating input max-min
Heating output max-min
Efficiency at Maximum Thermal Capacity
(see Installation Instructions)
CENTRAL HEATING
Operating Temperature max-min
Maximum-Minimum Heating Pressure
Built-in expansion vessel - Total capacity
ELECTRICAL DATA
Electrical Supply/Frequency
Power Consumption
Protection of Electrical System
CATEGORY
Nominal Pressure/Methane Gas (G20)
Nominal Pressure/Liquid Gas (G30-G31)
kW
kW
%
°C
bar
litres
V/Hz
W
IP
mbar
mbar
15.4
14.1
82.4
82-42
3-0.7
6
230/50
115
X4D
20
30-37
11.6
10.5
81.3
82-42
3-0.7
6
230/50
105
X4D
20
30-37
15 kW
10 kW
22.7-10.0
21.0-8.7
83.7
82-42
3-0.7
6
230/50
105
X4D
20
30-37
21 kW
29.8-12.0
27.8-10.5
84.2
82-42
3-0.7
6
230/50
155
X4D
20
30-37
28 kW

6
CONTROL PANEL
10 RFFI / 15 RFFI
21 RFFI /28 RFFI
FR011A

2. OPERATING INSTRUCTIONS
CAUTION
Installation, start-up, adjustments and
maintenance must be performed by a
competent person only, in accordance
with the current Gas Safety (Installation &
Use) Regulations and the instructions
provided. Improper installation may
cause damage or injury to individuals,
animals and personal property, for which
the manufacturer will not be held liable.
To ensure efficient and safe operation it is
recommended that the boiler is serviced
annually by a competent person.
If it is known or suspected that a fault
exists on the appliance, it must not be
used until the fault has been corrected by
a competent person.
7
LEGEND:
A - On/Off button
B - On/Off L.E.D. green (frost
protection active)
C - Central Heating button
D - Cental Heating active
L.E.D. green
E - Ignition failure (lockout)
and/or overheat reset button
F - Ignition failure (lockout) and/or
overheat L.E.D. red
G - Central heating temperature
adjustment
H - Energy Saving System (ESS)
I - Knock-out for time clock
J - Heating system pressure gauge

8
HELPFUL SUGGESTIONS
To get the most out of your boiler, we have
provided you with some useful advice on
proper use and maintenance:
- Periodically check the system pressure
using the pressure gauge “J”, make sure
that the pressure is between 1.0 and 1.5
bar (the blue part on the gauge) when the
system is off and cool. Consult your installer
for checking and refilling the system if the
pressure value is under 1.0 bar.
J
- The outer panels of the units case must
only be cleaned with a damp cloth. Do
not use abrasive cleaners. The control
panel can be wiped with either a damp
or dry cloth. Spray polishes must not be
used on the control panel surface or
knobs. Care must be taken in preventing
any liquid entering the appliance.
PRACTICAL TIPS
- If the water is very hard, it is
recommended that a scale reducer be
added to the system so as to reduce the
formation of limescale in the boiler heat
exchanger. This will ensure that the
efficiency of the unit remains the same
over time, reducing gas consumption
UT013Af

Ignition procedure
Push the button “A” the green L.E.D. “B”
will illuminate indicating that the boiler is
supplied with electricity.
Push the button “C” the green L.E.D. “D”
will illuminate indicating that the boiler is
operating for central heating production.
9
and maintenance costs.
- If the boiler should be out of use for a
prolonged period, it is recommended
that the electrical power supply be
disconnected and that the external gas
cock be closed. If low temperatures are
expected, the boiler and system pipe
work should be drained in order to
prevent frost damage.
- To improve comfort and take full
advantage of the heat produced by the
boiler, it is recommended that an
external (room) thermostat be installed.
- It is good practice to clean and ser vice
the appliance and central heating
system every year.
Call an Authorised Service Centre.
B
A
C
D
UT013Aa
UT013Ab

10
E
F
The centralised electronic control unit will
ignite the burner, without any manual
intervention but in response to the request
for heating. If, after approximately 10
seconds, the burner has not ignited, the
boiler safety devices will shut off the gas
and the red L.E.D. “F” illuminates. To reset
the ignition system, the reset button “E”
must be pressed and released. Should the
boiler fail to ignite a second time, check
that the external gas cock is open. If the
problem persists, contact an Authorised
Service Centre.
Adjusting the heating
It is possible to set the temperature of the
heating system by adjusting the knob “G”
between 1 and 5 until the stop on the
“ECO” position. This will var y temperature
from approximately 40˚C to about 65˚C.
To obtain a higher temperature it is
necessary to turn the Energy Saving System
(ESS) screw “H” clockwise with a small
coin. The knob is now free to turn to the
MAX position,
which represents
a temperature of
about 80°C.
G
UT013Ac
UT013Ad

Turning off central heating
T o turn off the central heating, push the “C”
button and the green L.E.D. ”D” will go off.
The boiler will remain electrically supplied
and frost protection will be active for
temperatures below 6°C.
C
D
11
External (room) thermostat
control
If an external (room) thermostat is installed,
it is recommended that the temperature of
the heating system be set (by means of the
knob “G”) at the “ECO” position. This will
allow the regulation of the external
temperature to operate effectively and
obtain energy efficiency and good
performance
from the boiler.
G
UT013Ag
UT013Ab

12
Turning off the boiler
To turn the boiler off, push the button “A”
the respective green L.E.D. “B” will go off.
Close the gas cock located under the boiler
and turn the electricity supply switch
(located outside the boiler) to the OFF
position.
B
A
3. USEFUL INFORMATION
AND TROUBLESHOOTING
Boiler shutdown situations
The boiler is equipped with safety devices
that intervene in certain situations and shut
it off. Most of these situations are
communicated by means of the red
L.E.D.“F” and at times the user may be able
to remedy them.
Shutdown due to ignition failure
In the event that the automatic ignition of
the burner has failed, the red L.E.D. “F” will
illuminate. In order to reset the ignition, the
button “E” must be pressed and released.
UT013Aa

to allow the exchanger to cool down, then
press and release the reset button “E”.
If this situation occurs frequently, contact an
Authorised Service Centre.
Shutdown due to insufficient
system pressure
In the event of insufficient water pressure in
the heating system, a safety device will
shutdown the boiler. Check the system
pressure on the pressure gauge “J” and if
it is less than 0.4 bar refill the system to 1.5
bar (consult your
installer for checking
and refilling the
system). Once the
system pressure is at
J
13
Should the boiler fail to ignite a second
time, check that the external gas cock is
open. If the problem persists, contact an
Authorised Service Centre.
Shutdown due to overheating
In the event that the safety limit is exceeded
for the temperature of the water in the
boiler’s primary exchanger, the thermostat
shuts off the boiler and the red L.E.D. “F”
illuminates.
T o remedy this situation, wait a few minutes
E
F
UT013Ac
UT013Af

14
the correct level the boiler will ignite
automatically. If there are frequent drops in
pressure within the system, have a plumber
check the heating system for possible water
leaks.
Temporary shutdown due to
defective discharge of exhaust
fumes
The boiler is fitted with safety devices,
which in the event of a defective discharge
of exhaust fumes, automatically interrupts
the gas supply, thereby shutting off the
boiler.
The shut-off of the boiler is temporary for a
period of about 15 minutes.
Once this time period has passed and the
discharge state of exhaust fumes has
returned to normal, the boiler automatically
turns back on.
Important!
If this situation occurs frequently, contact an
Authorised Service Centre. so that they
may check that the exhaust fumes are
being expelled correctly and that the area
is ventilated properly.
Frost protection
The boiler is fitted with a thermostat which,
in the event that the water temperature
goes below 6°C, the burner turns on at
minimum power until the water in the boiler
has reached a temperature of about 20°C.
This device is only activated when the
boiler is operating perfectly and:

the other, one of our Authorised Service
Centres should be contacted.
6. TIME CLOCK
A time clock for central heating is available
as an accessory kit and can be mounted
via the knock-out “I”. The installation of this
should only be
undertaken by a
competent person
and in accordance
with the kit
instructions.
I
15
- the system pressure is sufficient;
- the boiler is powered electrically;
- gas is being distributed.
4. MAINTENANCE
Schedule an annual maintenance check-up
for the boiler with a competent person.
Correct maintenance always results in
savings in the cost of running the system.
5. CHANGE OF GAS TYPE
Our boilers are designed to function either
with Natural Gas (methane) or LPG gas. If
you need to changeover from one gas to

Cod. 23 99 84 1548 112
Manufacturer: Merloni TermoSanitari SpA - Italy
Commercial subsidiary: MTS (GB) LIMITED
MTS Building
Hughenden Avenue
High Wycombe
Bucks HP13 5FT
Telephone: (01494) 755600
Fax:(01494) 459775
Internet: http://www.mtsgb.ltd.uk
E-mail: info@mtsgb.ltd.uk
Technical Service Hot Line: (01494) 539579