OSO TERMO RS-M User manual

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
TERMO ELECTRIC BOILER
INSTALLATION MANUAL
OSO TERMO RS -M

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Contents
1. Introduction ....................................................................................................................... 1
1.1. Applicable documents................................................................................................. 1
1.2. Retention of documents .............................................................................................. 1
1.3. Features & benefits..................................................................................................... 1
1.4. Operation of domestic hot water (where applicable).................................................... 1
1.4.1. Suitability.............................................................................................................. 1
1.4.2. Operation on S-plan system ................................................................................. 1
2. Termo M range.................................................................................................................. 2
2.1 Key to Termo boilers.................................................................................................... 2
2.2 Technical data ............................................................................................................. 3
2.3 Power supply characteristics 240V............................................................................... 3
3.0. Installation ...................................................................................................................... 4
3.1. Content included in delivery ........................................................................................ 4
3.2 Standards & Regulations ............................................................................................. 4
3.3. Physical Installation site .............................................................................................. 4
3.3.1 Select position for boiler ........................................................................................ 5
3.3.2 Fitting the boiler hanging bracket........................................................................... 5
3.3.3 General recommendations when handling............................................................. 5
3.3.4. Removing/fixing the front and top case................................................................. 5
3.4. Plumbing & Heating installation & commissioning....................................................... 6
3.4.1 Installation ............................................................................................................. 6
3.4.2 Ancilliary components............................................................................................ 6
3.5. Connection to the electrical mains supply ................................................................... 7
3.6. Connecting external controls....................................................................................... 8
3.6.1 Connect room thermostat/programmer .................................................................. 8
3.6.2. Connecting external pump on TERMO RS boilers ................................................ 8
4. Commissioning.................................................................................................................. 8
4.1. Control panel key ........................................................................................................ 8
4.2 Protection from freezing ............................................................................................... 9
5. Fault finding guide ............................................................................................................10
6. Maintenance.....................................................................................................................15
6.1. Periodic checking.......................................................................................................15
7. After Sales service information .........................................................................................15
8. Cascade power limiter ......................................................................................................15
9. OSO Hotwater UK Ltd ......................................................................................................15
10. Appendices.....................................................................................................................15
10.1 Termo RS-M with space heating and water heating ..................................................16
10.1.1. Hydraulic diagram Termo RS-M ........................................................................16
10.1.2. Electric diagram Termo RS-M............................................................................16
10.1.3. S-plan wiring layout ...........................................................................................17
10.2 Termo RS space heating only ...................................................................................17
10.2.1 Hydraulic diagram Termo RS-M .........................................................................17
10.2.2. Electric diagram Termo RS-M............................................................................18
10.2.3. S-Plan wiring layout Termo RS-M......................................................................18

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 1
Terminology used in this manual
The central heating boiler water circuit is called primary
The domestic hot water is called secondary (dhw)
1. Introduction
Thank you for purchasing the Oso Termo range electric central heating boiler.
To ensure a correct and safe installation and economical use, please read these instructions thoroughly before
installation.
1.1. Applicable documents
The following additional documents are provided with the appliance:
For the owner of the system:
Instructions for use
Warranty card
For the qualified technician:
Instructions for installation
Electrical drawing for the appliance
1.2. Retention of documents
Please pass on this installation manual to the owner of the system. The owner should retain the manuals so that
they are available when required.
1.3. Features & benefits
TERMO products are modulating and economical central heating boilers that may be used as independent or
additional source of heat.
The boiler provides wet system central heating by passing the primary water over the immersion heaters. Heating
elements are located on under-side of boiler ensuring elements are constantly immersed in heating medium
(water with appropriate inhibitor). Power is modulated automatically to control 1, 2 or 3 immersion elements with
built in step regulator or manually with switches on the control board.
The boiler operates on principle of rapid heating smaller water quantities, energy use is 100% efficient.
Power outputs available are 7.2, 10.8, 14.4 kW.
The boiler has an automatic pump overrun for both central and water heating that prevents a build up of heat in
the boiler. The boiler reservoir is insulated with 19 mm self-extinguishing Armaflex insulating material, which is
sufficient to direct the heat only to the heating system. Temperature operation can range from 20 oC to 90 oC.
1.4. Operation of domestic hot water (where applicable)
1.4.1. Suitability
Termo RS-M boilers are able to heat a central heating system containing space heating and a separate indirect
water storage cylinder using an S-plan system.
Termo RS-M boilers can also be used in a space heating only situation where water heating can be achieved by a
separate stand-alone direct water storage cylinder. OSO believe that this is a simpler system that is more suitable
in most domestic circumstances and will allow use of economy electricity tariffs, thus saving on water heating fuel
costs.
1.4.2. Operation on S-Plan system.
There is no DHW priority built into the boiler. A standard S-plan system will allow heating and hot water circuits to
be heated on demand. If a DHW priority is required, certain central heating programmers will offer this.
Recommended temperature inside boiler while heating domestic hot water is 75 oC – 80 oC.
Observe Honeywell ST6400 manuals for more detailed description of domestic hot water parameters.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 2
2. Termo RS-M
2.1 Key to Termo RS-M
1. Primary flow 7. Control panel 13. Drain valve (not supplied)
2. Primary return 8. Cable entry point 14. Isolation valves (not supplied)
3. External boiler jacket 9. Contactors and RCD switch 15. Manual venting valve (not supplied)
4. Boiler 10. Charge and discharge valve
5. Armaflex Insulation 11. Pocket with temperature probe
6. Immersion heaters 12. Safety valve (supplied loose)

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 3
RS - M
2.2 Technical Data For Termo Rs - M Boilers
Power
kW
Capacity
Lit.
Dimensions
mm
Weight
kg
Maximum
oprerating
pressure
MPa (bar)
Connection Power supply
7.2
10.8
14.4
6
A 330
B 750
C 230
D 100
E 57
F 126
21.4 0,25 (2,5) 3/4” 240V N ~ 50/60 Hz
2.3 Power supply characteristics 240V
POWER nominal
current
MCB Rated short-circuit
breaking capacity
Icn (EN 60898)
Rated short-circuit
breaking capacity
Icn (IEC 947-2)
Cable size* RCD switch
type
7.2 kW 30 A B32-1 3 x 6 mm240-2/0.03 A
10.8 kW 45 A B50-1 3 x 10 mm263-2/0,03A
14.4 kW 60 A B63-1
10 kA 15 kA
3 x 16 mm280-2/0,03A
min. conductor's cross-section in mm2is based on maximum length of 20 m. Cable sizes must be
selected according to latest version of IEE wiring regulations.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 4
3.0. Installation
3.1. Content included in delivery
TERMO boilers are delivered pre-assembled. Check
that all parts have been delivered intact. For exact
list of parts see figure and table below. If parts are
damaged or missing, please consult Oso Hotwater
UK Ltd.
Contents included with delivery
Item Description
1 TERMO boiler
2 Instructions
Electrical drawing, Warranty card
3 Hanging bracket
4 Safety valve (not fitted to boiler in case of TERMO RS)
Table of contents included with delivery
3.2 Standards & Regulations
The Oso Termo range of boilers are BEAB approved and CE marked.
Health and Safety at Work Act 1974 - When working with Termo boilers, ensure that protective clothing
and equipment is used appropriate to parts that may considered hazardous to health and safety
Control of Substances Hazardous to Health (COSHH 1988) - Glues, paints and sealants are used in the
manufacture of this product and present no known hazards when used in the manner for which they are
intended.
The guarantee is only valid if the following the following conditions are observed:
The boiler must be installed by a registered engineer to comply with current building regulations, IEE
electrical wiring regulations (BS 7671), local authority regulations, water supply regulations and health
and safety at work regulations.
Other Relevant British/European standards should be adhered to, including
BS 5449 - Specification for forced circulation hot water central heating for domestic premises,
BS 7593, treatment of water in domestic hot water central heating systems
3.3. Physical Installation site
IMPORTANT - MOVING THE BOILER EXCEEDS THE RECOMMENDED WEIGHT FOR A ONE MAN LIFT.
The boiler must be handled and transported carefully and stored in a safe, dry place.
TERMO RS-M is designed for wall installation in an upright position. Wall brackets are provided on the back of the
boiler. The boiler should be fixed in position on a suitable load-bearing wall prior to pipe connection.
The boiler should be fitted in a dry place not subject to extremes of temperature. Cylinder cupboards and kitchens
are acceptable but bath or showers rooms are not.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 5
3.3.1 Select position for boiler
The boiler should preferably be installed on the lowest point in relation to the installation. This ensures that
elements are always immersed in water and there is no danger of burning out.
When positioning the boiler, ensure there is
adequate space surrounding to allow for pipe
connection, ventilation, servicing and replacement
of components including the immersion heaters.
Refer to diagrams below for guidance.
Access is required to the control panel connections
at underside of the boiler and the power supply
connection, located at left bottom side of boiler.
Ensure the boiler is in a location where it will not be
affected by water drips or splashing.
Ensure that ventilation to the boiler is not impeded
by towels, linen etc placed very close to the boiler.
Do not place towels or linen on top of the boiler.
The figure below shows minimum recommended
clearances
Recommended minimal distances
3.3.2 Fitting the boiler hanging bracket
Fix the hanging bracket (see page 9 No. 3) to the wall using suitable plastic plugs and M8 or M10 screws (not
supplied). Decide the position of the bottom of the boiler, giving due consideration to the recommended minimum
clearance and then drill holes to accept the boiler mounting plate.
Screw points should to be drilled 624mm above the bottom of the boiler casing.
Note:
If the boiler is to be fitted in a timber framed building ensure that the bracket is secured to a substantial
part of the timber frame capable of taking the weight of the boiler.
3.3.3 General recommendations when handling
Clear the route before attempting the lift. Ensure safe lifting techniques are used – keep back straight – bend
using legs. Keep load as close to body as possible. Do not twist – reposition feet instead. If 2 persons performing
lift, ensure coordinated movements during lift. Avoid upper body/top heavy bending - do not lean
forward/sideways. Recommend wear suitable cut resistant gloves with good grip to protect against sharp edges
and ensure good grip. Always use assistance if required.
Positioning of Appliance for Final Installation
Lift up boiler (3) above hanging bracket (2)
Gently lean it to the wall (1)
Slide it down to hanging bracket (2).
Wall mounting
3.3.4. Removing/fixing the front and top
case
1. Grasp the front case by its sides
2. Pull it towards the front and remove it by lifting it
off the unit
3. Push top cover towards back
4. Lift it off the unit.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 6
3.4. Plumbing & Heating installation & commissioning
3.4.1 Installation
Fit the supplied safety valve to the heating return point on the installation– see point 12 page 2 diagram. Ensure
that no valve is placed between the safety valve and the boiler.
To avoid draining the entire primary system during boiler maintenance it is recommended that isolation valves are
fitted to the flow and return pipes immediately below the boiler.
Connect the primary flow and return pipes for the central heating system to the labeled connections on the boiler.
Connections can be made using wither the top or bottom connections as shown on page 2.
Connect the mains water supply via a filling loop to the charge and discharge valve on the boiler incorporating a
stop valve and double check valve which must be left disconnected after commissioning.
Drain taps must be located in accessible positions which permit the draining of the whole system including the
primary and the secondary (dhw) system.
Any water loss from the system should be replaced from the filling loop connection.
When draining the boiler allow air in using the boiler venting valve. Do not drain the boiler by opening the
pressure relief valve.
All capillary joints in all DHW pipework must be made with lead free solder.
RS-M is a self contained system boiler that manages heating flow to the radiators and/or under floor and also
supplies heat to an indirect domestic hot water cylinder via an S-plan system. External motorized valves and an
automatic bypass are required for the S-plan system.
Termo boilers can also be used on an open vented central heating system.
Wherever possible all pipe work should be insulated to help prevent heat loss and possible freezing, particularly
where pipes are run through roof spaces and ventilated under-floor spaces.
3.4.2 Ancilliary components.
On RS – M boilers a boiler pressure gauge, circulation pump and expansion vessel must be fitted. The expansion
vessel should be sized to the total system volume. The water capacity of the boiler itself is 6 litres.
Diagram of recommned pump on RS-E for radiator heating Diagram of recommned pump on RS-E for underfloor heating
To comply with Part L of building regulations, a room thermostat must be fitted with the boiler. The room
thermostat should not be sited over radiator or other heat emitter and should not be in direct sunlight.
Thermostatic radiators valves may also be used, but should not be fitted in the same room as the room
thermostat.
After the central heating circuit has been laid open all service valves, flush pipes through and check for leaks
before commissioning and introduce the correct inhibitor for a central heating circuit in accordance with BS7593.
Commission the boiler slowly to allow air to escape through the automatic air vent. Remove air from pump using
front screw on pumps.
Pressurize the system to 1.5 bar.
Where the boiler is being retro-fitted to an existing installation, it is equally important to flush the system and
commission using inhibitor to BS7593.,
TERMO boilers are fitted with an automatic and manual air vent. The boilers are also equipped with an air-
indicator which detects the presence of air in the boiler. If air is detected and It exceeds the permitted level, air-
indicator switches off immersion heaters and circulation pump remains active, so that air is allowed to escape
easily. Once the air is dispelled the immersion heaters will be active.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 7
3.5 Connection to the electrical mains supply
Before working with the appliance, turn off the power supply (MCB) and secure against restart.
This device must be earthed.
Check that the electrical supply to the building has sufficient current and voltage to supply the boiler and other
appliances to be used.
Miniture circuit breakers (MCB) must be fitted in the wiring prior to the boiler. For MCB ratings see table on page
3. Connect the boiler to the mains using a double pole linked switch with 3mm contact gap in both poles.
Measure exact voltage between L and N lines prior to connecting boiler, if it 10% higher than nominal voltage on
appliance, appliance itself can be damaged.
Central heating control equipment – please note that all heating control
equipment (programmer, timer, thermostats etc MUST be supplied with power
from the boiler connections plate – see section 3.6. DO NOT supply controls
with power directly from the mains supply.
To connect power supply cable power connection protection cover must be removed by unwinding two nuts M6
and pulling protection cover out. Power cable must be connected directly to RCD, earth must be connected to
separate terminal. After connecting power cable and control units, protective cover must be replaced and
secured.
For 240V power supply RCD switch in boiler
from 7.2 up to 14,4 kW is 2-pole
Power supply connection RCCB (RCD) connection close-up
Power cables must be connected from bottom side of boiler with the use of provided plastic
inducer for electric cable.
Ensure that the wires are securely fixed.
The appliance must be connected to mains electricity and tested according to current IEE regulations. An NICEIC
inspection and completion certificate must be issued.
The appliance must be connected to mains electricity and tested according to current IEE regulations. An NICEIC
inspection and completion certificate must be issued.
All exposed pipework must be earthed according to current IEE regulations

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 8
3.6. Connecting external controls
External controls (Programmer, thermostats, pump, zone valves) must be supplied with power from the green
boiler connections plate. See diagram (right) via removable connector as shown below
Terminals OUTDOOR TEMP. DOMESTIC WATER,
3 HW ON & HW PUMP are not used.
L, N & PE Power supply to control unit - (3 port
green)
4 CH ON – switched live from external unit for
heating & DHW (2 port grey/black)
L, N & PE to Central heating pump – (3 port
grey/black)
Connection plate
3.6.1 Connect programmer/room thermostat
Supply power to central heating programmer/room stat assembly from L, N, PE on connections plate. Use a
junction box if necessary.
From this point follow thermostat manufacturer’s instructions to connect programmer/stat assembly & S-Plan
system.
The boiler is supplied with a fixed link between L and 4. If an external control device (room thermostat and/or
programmer) is used, remove this link.
Switched live from room thermostat and water heater thermostat must be connected to 4 CH ON.
3.6.2. Connecting external pump on TERMO RS boilers
TERMO RS boilers do not have inbuilt central heating pump and pump for domestic water cylinder. Empty
terminals on connection plate are provided to fit external pumps.
Terminal CH PUMP is provided for central heating pump for heating and DHW. Connect pump L, N, PE wires to
the appropriate connection ports.
Termo RS-M is fitted with an automatic pump overrun.. Factory settings is 3 min
4. Commissioning
4.1. Control panel key
1 – Indicator of temperature /pressure in boiler
2 – Working thermostat
3 – Switch for the 2nd and 3rd operation stage
4 – Cutout thermostat with manual deactivation
(operates at 100 oC)
5 – Air Indicator/Low voltage indicator
6 - Switch for ON/OFF and 1st heating stage
7 – Fuse (2.5A) protecting pump and switches
8 – Indication of heater operation

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 9
Switching boiler on
Test the RCD switch by pressing T button on it. Reset the RCD switch.
Switch on boiler at switch (6). Switch will illuminate. First power stage activates if there is heating demand.
If the boiler is heating, heaters in operation light (8) will illuminate.
Switches (3) manually enable activation of second and third immersion heaters in boiler.
These switches will illuminate if heating demand activate these heaters.
Boilers with 3 stages have soft start for second and third stage and switches (3) have only limiting function.
If heaters are not working and boiler is in standby only ON/OFF light is on.
Normal practice is to have switches 6 & 3 on and to leave the control system to modulate boiler. Switching off the
2nd or 3rd stage will manually limit boiler power and may provide insufficient heat for the property.
Adjustment of desired temperature of central heating
Select desired temperature in boiler using working thermostat (2). Recommended temperature is about 60ºC (12
clock position). Thermostat range is 20ºC to 90ºC.
If boiler is switched on with working thermostat in off position (6 o’clock) central heating pump will operate.
If working thermostat is turned up and there is no heating demand, pump will stop.
If working thermostat is turned up and there is heating demand, pump will continue and immersion heaters will
heat as shown on light8. Activation of 2nd & 3rd immersion heaters is shown by illumination of their lights 3.
Air in the boiler/ Low Voltage (5), red light
Light will illuminate red if air appears in the boiler. The boiler shuts down automatically. To continue operation,
vent the boiler. When venting is completed the boiler restarts automatically.
If the voltage drops below 180V per phase, low voltage protection light (5) illuminates, the boiler automatically
switches off in order to protect electronics and contactors inside the boiler. The boiler will automatically restart
when the network voltage exceeds 180V.
Cutout thermostat - turning on
Cutout thermostat (safety thermostat) (4) protects the boiler against rapid increase of temperature above 115°C.
The fuse turns off the boiler and trips the RCD switch.
To restart boiler. Unscrew protection cover (4) from the cutout thermostat and press the red key.
Cut-out cannot be reset until the temperature of the boiler cools.
NOTE: If the room thermostat is fitted, boiler will only operate if thermostat is calling for heat.
4.2 Protection from freezing
Freezing protection is dependent on the room thermostats. To protect a property from freezing when the
occupiers are away, the boiler must be left in the ON position with the central heating programmer and/or room
thermostat set to freezing protection. If there is no preset freezing protection state on the programmer/thermostat,
lower the set temperature in the property to 5°C. This will reduce energy consumption whilst offering system
freezing protection.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 10
5. Fault finding guide
The boiler is not
operating or radiators
are cold
Is the boiler
switched ON?
Switch boiler ON
NO
Is the green
LED light
ON?
YES
Are the MCB
(on master switch
board) and RCD
(in boiler and master
switch board)
switched ON?
NO
Switch ON MCB
NO
Switch ON RCD RCD can't be
switched ON
YES
YES
Reset safety thermostat
and try again to switch
RCD ON
NO
Electrical part of boiler
(heater, switch, relay)
is faulty
Does
DISPLAY
show temperature
inside boiler?
NO
NO
YES
Is the
temperature of water
same as
desired?
YES
Wait for boiler to heat up
NO
Is the room
thermostat switched
ON?
YES
Switch ON room
thermostat
Check isolation valves
NO
YES
Faulty control panel
NO
Please check the following before going through fault finding
flowchart.
Check the installation is correct.
All isolating valves are open.
The system is full of water (pressurised) and purged of air.
Programmer and controls outside of boiler are on.
Check the electrical supply is connected correctly and present
YES
One or more
heaters are faulty

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 11
When switched on,
switches on control
panel show the
voltage, however the
boiler does not heat
Is the
limiting thermostat
activated?
Safety thermostat can be
activated if air is present in
installation or operation thermostat
is faulty or relay is blocked
Is the room
thermostat
too low?
YES
YES
Is the
operating thermostat
defective?
NO
NO
Replace the operating
thermostat with new
YES
Please check the following
before going through fault
finding flowchart.
Check the installation is
correct.
All isolating valves are open.
The system is full of water
(pressurised) and purged of
air.
Programmer and controls
outside of boiler are on.
Check the electrical supply is
connected correctly and
present
NO
Adjust correct temperature
Is the
RED lamp
''air in the boiler''
illuminated?
Check the water pressure
and purged of air
YES
NO
Is the
voltage present
on immersion
heaters
Replace the immersion
heaters
YES

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 12
Boiler ''roars''
while heating
Check the
water pressure
and vent the
central heating
system
Defective immersion heaters
- change the heaters
YES
Please check the following
before going through fault
finding chart:
Check the installation is
correct.
All isolating valves are open.
The system is full of water
(pressurised) and purged of
air.
Programmer and controls
outside of boiler are on.
Check the electrical supply is
connected correctly and
present
Central heating
system was not
vented properly
Lower the speed on
central heating pump
(see guide below)
YES
NO
RCCB switch cannot
be switched ON
Check existanc
e
of resistance
between terminals N,3,5,7
or RCCB switch and PE
Find component which has
contact between earth (PE) and
change it.
YES
Please check the following
before going through Fault
finding chart.
Check the installation is
correct.
All isolating valves are open.
The system is full of water
(pressurised) and purged of
air.
Programmer and controls
outside of boiler are on.
Check the electrical supply is
connected correctly and
present
Check the
status of safety
thermostat, try to
reset it
Switch on RCCB switch
YES
NO
Change the RCCB switch
NO

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 13
Central heating is
working but domestic
hot water (DHW)
is not working
Is the relay RHW
in ON possition?
Is the votage
present on DHW
pump therminals?
NO
YES
NO
Please check the following
before going through Fault
finding chart.
Check the installation is
correct.
All isolating valves are open.
The system is full of water
(pressurised) and purged of
air.
Programmer and controls
outside of boiler are on.
Check the electrical supply is
connected correctly and
present
YES
Find and restore
break of connection
Are the parameters
for DHW on
control panel or/and external
programmer
correct?
Change parameters
NO
YES
Check external
programmer
NO
Change the
relay RHW
YES
Change the DHW pump
Is the voltage
present on terminals
a1(L) and a2(N)
of relay RHW?

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 14
Domestic hot water is
working but
central heating
is not working
Is the relay RCH
in ON possition?
Is the votage
present on CH
pump therminals?
NO
YES
NO
Please check the following
before going through Fault
finding chart.
Check the installation is
correct.
All isolating valves are open.
The system is full of water
(pressurised) and purged of
air.
Programmer and controls
outside of boiler are on.
Check the electrical supply is
connected correctly and
present
YES
Find and restore
break of connection
Are the parameters
for central heating on
control panel or/and external
programmer
correct?
Change parameters
NO
YES
Check external
programmer / room
thermostat
NO
Change the
relay RCH
YES
Change the CH pump
Is the voltage
present on terminals
a1(L) and a2(N)
of relay RCH?

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 15
6. Maintenance
6.1. Periodic checking
The safety valve should be checked annually, preferably before the heating season to ensure correct operation
and avoid accumulation of lime scale. It is not recommended to annually drain the system to protect the system
from freezing as refilling with fresh water will increase the risk of limescale attack
We recommend inspection of the boiler once a year by an authorized service engineer. This service is not
included in the guarantee. During the inspection all electric and water connections should be tightened, the
system should be vented and – if necessary – filled up, valves and general functionality of the device and safety
valves should be checked.
When cleaning the product do not use an aggressive liquid as e.g. gasoline, kerosene or solvent. For the external
shell and decorative cover, liquid for cleaning plastics or dish washing media may be used. Control panel should
be cleaned with dry or moist cloth (not wet).
7. After Sales service information
If after using the fault-finding guide above the problem cannot be rectified by the installation engineer on site, a
qualified Oso Service Engineer is available during normal office hours to attend a breakdown.
A charge will be made if:
There is not a fault with the Termo boiler or the breakdown was caused by incorrect installation of the product that
does not conform to the installation manual.
Components fitted on the system that were not supplied by Oso are preventing the satisfactory operation of the
Termo boiler.
The terms and conditions of the guarantee have not been satisfied or the warranty period of the Termo boiler has
expired.
Many boiler manufacturers find that a very large proportion of service calls are not caused by a product fault.
Please read the fault finding guide and the other instructions in this manual carefully.
Oso will not accept unauthorized invoices from any third party for repair or service work to Termo boilers.
8. Cascade power limiter
Where there are other high load electrical appliances e.g. electric ovens, electric showers etc fitted in the property
with the boiler there is a possibility of overload on the electrical system. The Oso cascade power limiter is a
unique device that continually monitors the electricity consumption of the property and if required will power down
the boiler temporarily to prevent overload.
9. OSO Hotwater UK Ltd
Oso Hotwater UK Ltd
E15, Marquis Court
Team Valley Tarding Estate,
Gateshead
Tyne & Wear
NE11 0RU
Tel: [phone]
Fax: [phone]
www.oso-hotwater.com
[e-mail]
[e-mail]
[e-mail]
10. Appendices
Appendices with further technical information are displayed on the following pages.
These appendices should be used in conjunction with the information supplied elsewhere in the manual and show
additional schematic and electrical diagrams to assist in the installation of Termo boilers into different central
heating systems. Advice is given for a variety of standard systems commonly used in the UK, however the list is
not exhaustive and OSO Hotwater UK Ltd cannot guarantee that the advice will be correct for any particular
system.
All diagrams are shown for informational purposes only. Diagrams are not comprehensive and
do not show every system detail.

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 16
10.1 Termo RS-M with space heating and water heating
10.1.1. Hydraulic diagram Termo RS-M
10.1.2. Electric diagram Termo RS-M

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 17
10.1.3. S-plan wiring layout
10.2 Termo RS space heating only
10.2.1 Hydraulic diagram Termo RS-M

INSTRUCTIONS FOR INSTALLATION
The company reserves the right to make alterations without prior notice
Page 18
10.2.2. Electric diagram Termo RS-M
10.2.3. S-Plan wiring layout Termo RS-M