The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 2
1. INTRODUCTION ................................................................................................................................. 3
1.1. APPLICABLE DOCUMENTS ............................................................................................................................. 3
1.2. RETENTION OF DOCUMENTS.......................................................................................................................... 3
1.3 TERMO E CONCEPT ........................................................................................................................................ 3
2. TERMO E RANGE .............................................................................................................................. 4
2.1. KEY TO TERMO BOILERS ............................................................................................................................ 4
2.1.2 PLUS - E...................................................................................................................................................... 4
2.2 EXPANSION VESSEL CHARACTERISTICS (PLUS AND PTV BOILERS).............................................................. 5
3. SUPPLY CHARACTERISTICS 240V N ~ 50/60 HZ........................................................................... 6
4. INSTALLATION .................................................................................................................................. 6
4.1. CONTENT INCLUDED IN DELIVERY ................................................................................................................ 6
4.2 STANDARDS & REGULATIONS ....................................................................................................................... 6
4.3. PHYSICAL INSTALLATION ............................................................................................................................. 6
4.3.1 SELECT POSITION FOR BOILER..................................................................................................................... 7
4.3.2 FITTING THE BOILER HANGING BRACKET .................................................................................................... 7
4.3.3 RECOMMENDATIONS FOR HANDLING .......................................................................................................... 7
4.3.4 REMOVING/FIXING THE FRONT AND TOP CASE ............................................................................................ 7
4.4.1 INSTALLATION ............................................................................................................................................ 8
4.4.2 ANCILLARY COMPONENTS. ......................................................................................................................... 8
4.5 CONNECTION TO THE ELECTRICAL MAINS SUPPLY ......................................................................................... 9
4.6 CONNECTION PLATE FOR CONTROL EQUIPMENT, TEMPERATURE SENSOR & PUMP…………………...10
4.6.1 CONNECT ROOM THERMOSTAT/PROGRAMMER...........................................................................................10
4.6.2. FIT EXTERNAL TEMPERATURE SENSOR......................................................................................................10
5. SETTING UP BOILERS .................................................................................................................... 11
5.1 CONTROL PANEL (INCLUDING FAULT FINDING INDICATORS) ........................................................................11
5.2. CHOOSE TYPE OF HEATING (RADIATOR OR UNDER FLOOR HEATING)............................................................12
5.2.1 HYBRID SYSTEMS COMBINING RADIATOR AND UFH. ................................................................................12
5.3. ACTIVATING SYSTEM AND PROGRAMMING CENTRAL HEATING ....................................................................13
5.3.1 HEATING CURVES EXPLAINED....................................................................................................................14
5.3.2 TO SET CORRECT CURVE ............................................................................................................................14
5.3.3 SETTING INTERNAL TEMPERATURE…………………………………………………………………………...14
5.3.4 PROGRAMMABLE ROOM THERMOSTATS & SETTING VARIABLE INTERNAL TEMPERATURES........................15
5.5 PROTECTION FROM FREEZING .......................................................................................................................15
6. RECOMMENDED ANNUAL CHECKS (ALL BOILERS) ................................................................. 15
7. CENTRAL HEATING CONTROLS ADVANCED MENU.................................................................. 16
8. FAULT FINDING GUIDE................................................................................................................... 18
9. AFTER SALES SERVICE INFORMATION ...................................................................................... 20
10. TECHNICAL DATA......................................................................................................................... 21
11. OSO HOTWATER UK LTD............................................................................................................. 21
12. APPENDICES ................................................................................................................................. 21
12.3 – APPENDIX 3 - TERMO PLUS E .................................................................................................................21
12.3.1 SCHEMATIC DIAGRAM TERMO PLUS-E ............................................................................................................21
12.3.2 WIRING DIAGRAM TERMO PLUS-E…………………………………………………………………………….22
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 3
TERMINOLOGY USED IN THIS MANUAL
The central heating boiler water circuit is called primary
1. Introduction
Thank you for purchasing the Oso Termo E 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 Termo - E concept
The Termo Plus E is a wet system electrically heated boiler for space heating only. It is not suitable for use with
an indirect water heater and should not be used under any circumstances to heat domestic hot water.
The boiler provides wet system central heating by passing the primary water over the immersion heaters. The
immersion heaters are located on the under-side of boiler ensuring the elements are constantly immersed in the
heating medium (water with appropriate inhibitor).
Termo Plus E uses weather compensation/heat curve technology. An outside sensor supplied with the boiler
informs the boiler of the outside temperature. This information is used by the boiler to set a temperature in the
heating system. The colder the external temperature, the more internal heating is required.
The boiler is supplied with a range of heat curves built into its software. Once correctly set, the heat curve need
never be altered. Heat curves are set according to the insulation levels of the property. A poorly insulated house
will require a higher primary heating temperature.
Selecting the heating curves at the time of installation is a simple process for the installer. A table is shown on
page 13 indicating which heating curve is required for the building type. Once the heating curve is correctly set, it
should never require changing.
The heating curve will aim for the property to be heated to 22°C. Not all households wish for the same internal
temperature, if the residents of the property require a higher or lower temperature, the selected curve should be
offset up or down by the appropriate number of degrees. Full instructions are given on page 14.
A room thermostat (not supplied) must be installed to finely regulate internal temperatures.
Heat curve systems operate for longer periods at lower temperatures than traditional systems and can typically
make savings of up to 15% over a standard heating system. Heat curve systems are widely used in Europe but
relatively new in the UK.
Heating curves also vary according to radiator or under-floor heating. The factory set heating curve is for a
building constructed to 2000 building regulations with radiator heating. Many boilers therefore will not require
adjustment of heating curve.
The boiler will modulate 1, 2 or 3 elements to achieve the desired primary temperature. The boiler reservoir is
insulated with 19 mm self-extinguishing Armaflex insulating material, which is sufficient to direct the whole heat
only to the heating system.
The boiler operates by rapidly heating a small water quantity. Energy use is maintained at 100% efficiency.
No flue or fan required - Almost silent in operation - No bulk oil storage tanks required
No annual safety check required
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 4
2. Termo E range
2.1. Key to TERMO boilers
2.1.2 Plus - E
1. Primary flow
2. Primary return
3. External boiler jacket
4. Boiler
5. Armaflex insulation
6. Electrical heaters
7. Control panel
8. Cable entry point
9. Contactors
10. Expansion vessel
11. Circulation pump
12. Safety valve 2.5 bar
13. Automatic air vent (AAV)
14. Charge and drain valve
15. Boiler venting valve
16. Air-indicator
17. Manifold
18. RCD switch
19. Pocket with temperature probe
20. Pressure probe
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 5
Plus – E
Technical Data For Plus E Boilers
Power
kW
Boiler
Capacity
Litres
Expansion
vessel
L/bar
Dimensions
Mm
Dry
Weight
kg
Maximum
primary
operating
pressure
MPa (bar)
Connection
BSP male
Power supply
7.2
10.8
14.4
6 8 / 0,8
A 330
B 930
C 230
D 100
E 65
F 320
34.5 0,25 (2,5) ¾” 240V N ~ 50/60 Hz
2.2 Expansion Vessel Characteristics
Volume of
Expansion
Vessel
L
Maximum
Expansion
Vessel
Pressure
MPa (bar)
Pre-charge
Pressure
MPa (bar)
Maximum
Pressure
In heating
System
MPa (bar)
Max Height
Difference
in central
Heating
System
m
Effective
capacity of
Expansion
Vessel
L
Adsorption
Capacity
%
Maximum
amount of
water in
primary
system
L
Maximum
power of
Boiler
kW
8 0.4 (4) 0.08
(0.8) 0.3 (3) 10 4.0 50% 114 14.4
Values are related to working temperature range from 10°
°°
°C to 90°
°°
°C.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 6
3. Supply Characteristics 240V N ~ 50/60 Hz
POWER nominal
current
MCB Rated short-circuit
breaking capacity
Icn (EN 60898)
Rated short-circuit
breaking capacity
Icn (IEC 947-2)
Minimum
Cable size*
RCD switch type
7.2 kW 30 A B32-1 3 x 6 mm2 40-2/0.03 A
10.8 kW 45 A B50-1 3 x 10 mm2 63-2/0,03A
14.4 kW 60 A B63-1
10 kA 15 kA
3 x 16 mm2 80-2/0,03A
*min. conductor's cross-section in mm2 is based on maximum length of 20 m. Cable sizes must be
selected according to latest version of IEE wiring regulations.
4. Installation
4.1. 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 within delivery
Item Quantity Description
1 1 TERMO boiler
2 1 Instructions for electrical / plumbing installation, user guide and warranty card
3 1 (2) Hanging bracket
4 1 External temperature sensor
4.2 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 conditions are observed:
The boiler must be installed by a registered engineer to comply with current building regulations, current
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
Recommended pressure of central heating installation is 1.5 bar, maximum operating pressure is 2.5 bar.
4.3. Physical installation
IMPORTANT – MOVING, POSITIONING AND INSTALLING 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.
Plus – E is designed for wall installation in an upright position. Fixed 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.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 7
4.3.1 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 surrounding space to allow for pipe
connection, ventilation, servicing and replacement
of components. Refer to the diagram to the right 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 that bottom part of boiler is accessible to
change the immersion element.
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 minimum clearances.
4.3.2 Fitting the boiler hanging bracket
Fix the hanging bracket (see page 12 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 610mm
above the bottom of the boiler casing
Important 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.
4.3.3 Recommendations for 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. Oso recommend
wearing suitable cut resistant gloves with good
grip to protect against sharp edges and ensure
good grip. Always use assistance if required.
Lift up boiler (3) above hanging bracket (2)
Gently lean it to the wall (1)
Slide it down to hanging bracket (2).
4.3.4 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.
2
1
3
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 8
4.4 Plumbing & Heating installation & commissioning
4.4.1 Installation
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 labelled connections on the boiler.
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.
The Plus - E is a self contained system boiler that manages heating flow to the radiators and or under floor
heating system. Product diagram on page 4 display the expansion vessel and pumps.
Plus - E 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.
4.4.2 Ancillary components.
If the capacity of the in built expansion vessel on Plus - E is not sufficient for the heating system (indicated by
pressure increase of 0.6bar when system is heated), an additional expansion vessel can be installed external to
the boiler. This should be fitted to the return pipe as close as possible to the boiler.
To comply with Part L of building regulations, a room thermostat must be fitted with the boiler. This will work in
conjunction with the boiler software and outside temperature sensor to finely control the temperature in the
dwelling and minimize energy consumption. The room thermostat should not be sited in direct sunlight or close to
any heat emitter such as radiators. 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 installed 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.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 9
4.5 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.
Miniature circuit breakers (MCB) must be fitted in the wiring prior to the boiler. For MCB ratings see table on page
7. 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 4.6. DO NOT supply with power
directly from the mains supply.
In order to connect power supply cable power connection protection cover (1) 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 (3). After connecting power cable and control
units, protective cover (1) must be put in place and tightened.
For 240V power supply RCD switch in boiler
from 4,8 up to 14,4 kW is 2-polle
Power supply connection RCCB (RCD) connection close-up
Note: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.
All exposed pipework must be earthed according to current IEE regulations
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 10
4.6 Connection plate for control equipment, temperature sensor & pump
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 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)
Outdoor Temperature – (2 port green)
Connection for pump is factory fitted. (3 port black).
Connections plate
4.6.1 Connect room thermostat/programmer
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.
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.
4.6.2. Fit external temperature sensor
The external temperature sensor (delivered with boiler) must be fitted in a permanently shaded area to prevent
sudden temperature changes through exposure to direct sunlight. When fitting the sensor please observe arrow
marking top position (can be seen when protective cover is removed). The sensor is an integral part of the
temperature compensation principle and must be fitted as the boiler cannot operate correctly without it.
Use twin core cable diameter 0,6mm2 to 1,5 mm2, to connect external temperature sensor,
The boiler is supplied with a factory mounted resistor connected to the outside temperature sensor port that
simulates the outside temperature at -13ºC for testing purposes only. After installation and initial testing, the
resistor must be removed and wires from the external temperature sensor must be connected to the sensor port.
(Circled port on diagram below right).
protective cover
base
External temperature sensor
External temperature sensor connection point
on boiler's connection plate
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 11
5. Setting up Boilers
Switch boiler on
Test the RCD switch by pressing T button on it. Reset the RCD switch.
Plus - E – Space heating with outdoor temperature compensation
5.1 Control Panel (including fault finding indicators)
1. Display
Default display is of current primary temperature inside the boiler. Temperature range is -19oC (below -19oC the
display shows - -) up to + 99oC (above +99oC display blinks).
Following warning signals can be displayed:
• P1 – anti freeze protection for secondary (DHW) is active
• P2 – anti freeze protection for central heating is active
• o1 or c1 – thermal sensor for primary temperature isn't connected or is short-circuited
• o2 or c2 – thermal sensor for external temperature isn't connected or is short-circuited
2. Led diodes of heater stages in use
LED diodes light to show how many heating elements are active.
3. Led diode OK/air in boiler
If there is no air in the boiler, the diode lights green. If air appears in the boiler, the diode lights red and the
boiler shuts down. Upon de-aeration, the diode automatically changes the color to green and operation of the
boiler continues.
4. Led diode insufficient supply voltage
Lights red if the net voltage is below 170 V and the boiler shuts down.
5. Led diode for central heating
Indicates the operation of heating circulation pump, provided that the room thermostat is on.
6. Push button to adjust central heating programming.
7. Central heating switch (0 – standby, 1 – on)
11. Water pressure gauge for heating system.
12. Safety thermostat
IMPORTANT:
If an error is displayed on the LED display (1) the boiler will stop. If the error is corrected the boiler will
automatically continue operation.
If error o3 or c3 occurs, (see 1 above) the boiler will cut out. In this instance it is possible to operate the
boiler in central heating mode until the domestic hot water is operational. This can be done by switching
off the domestic hot water with switch number 9.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 12
5.2. Choose type of heating (radiator or under floor heating)
Factory default is for radiators. To change to under floor heating, follow instructions below.
1. Disconnect from mains supply
2. Remove front cover of boiler.
3. Remove perspex control panel cover (prize off with
screwdriver down channels at either side)
4. Remove control panel, (Push up from bottom and pull
out. Pull out whole of panel, there should be no need
to disconnect any wires connected to control panel)
5. Remove black plastic shroud at rear of control panel
by undoing 2 cross headed screws.
6. Control switches for heating curves are in the position
circled in the image to the right.
7. Default setting for radiators is as shown for under floor heating change to
8. Replace black plastic cover. Re-fit control panel. Re-fit panel protector. Re-fit the boiler front cover.
1
4
2 3
ON
OFF
Function
Pin 1 – ON Set heating type to under floor, curves from 0.1 to 0.9 are active, minimum boiler
temperature is set to 15ºC, maximum boiler temperature is set to 45ºC
Pin 1 – OFF
(Factory settings)
Set heating type to radiator, curves from 1 to 3 are active, minimum boiler temperature is set
to 25ºC, maximum boiler temperature is set to 90ºC
Pin 2 – ON Disable outdoor temperature compensation, user must manually select temperature in boiler
Pin 2 – OFF
(Factory settings)
Enable outdoor temperature compensation, default curve for radiator heating is 1.5 and 0.6
for under floor heating
Pin 3 Used during manufacturing process
Pin 4 Used during manufacturing process
5.2.1 Hybrid Systems combining radiator and UFH.
If the boiler is to be used to heat a hybrid system i.e. wet radiator system and under floor heating no alterations
should be made to the factory setting. In this situation a blending valve should be fitted in the under floor heating
manifold to reduce the flow temperature to maximum 50C.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 13
5.3. Activating system and programming central heating
Off mode - The boiler is connected to the electrical supply but the RCD switch (page 12) is off
Standby mode – the RCD switch is on but the central heating on/off and dhw switches on control panel are off
On mode – RCD switch, dhw and central heating switch are all on
Switch to on mode - Test the RCD switch by pressing T button on it. Reset the RCD switch
Operations with Honeywell or Danfoss control units:
With central heating programmer (Honeywell ST6400, Danfoss TP-9 7-day programmer or similar) it is possible to
program separate periods of central heating from periods for domestic water heating.
Switches 7 and 9 on electronic control panel have a different function when 7-day control unit for central heating
and sanitary water preparing is installed. In this case position ‘’0’’ is AUTO (operations as controlled by control
unit Honeywell/Danfoss) and position ‘’1’’ is MANUAL (operations are controlled by boiler’s control panel).
When sanitary water and apartment temperature rises to desired level, boiler automatically goes to standby
position (everything is switched of except standby led diode).
Factory defined curves
Sample of modified curve
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 14
5.3.1 Heating curves explained.
Heating curves take information from the outside temperature sensor and decides on the required primary
temperature in the heating system to maintain the desired internal temperature based on the insulation properties
of the building.
• The colder it is outside, the higher the temperature needed in the heating system.
• Poorly insulated (older) properties require more heat, hence a higher heating curve is selected.
Heating curves save energy. A correctly set curve will optimize savings. A curve set too low will result in a house
that feels cooler than desired. A curve set too high will not optimize savings.
Termo E boilers are supplied with a full range of curves to choose from.
The choice of a heating curve is dependent on the insulation levels in the building. Heating curves can be altered
at any time by the householder, but once correctly set, should never require adjustment. The best guide to
insulation levels is the age of the building, as insulation levels have steadily improved over time. The factory set
heating curve is for buildings built to 2000 building regulations and UK heating installation common practice.
The table below shows the suggested heating curves for properties of differing ages. If extra insulation has been
retro-fitted to a building, a lower heating curve will be appropriate.
5.3.2 To set correct curve
Turn central heating on (key 7).
Press key 6 UP and hold for five seconds
to enter curve selection menu. The set
curve blinks in the display. Press key 6 up
or down to alter curve selection in steps of
0,1, see the diagram on the front plate. If
there is no pressure on the key for more
than 5 seconds the curve displayed is
saved.
Construction date Radiator curve under floor curve
Pre 1970 2.0 0.9
1971 – 1990 1.8 0.8
1991 – 1999 1.6 0.7
2000 – 2005 1.5 0.6
2006 1.2 0.5
Factory default 1.5(mod) 0.6(mod)
Factory default curves have been modified specifically for UK heating design standard practice. If curve is altered
and default curve is then subsequently required, a factory reset is required. See instructions page 25.
5.3.3 Setting internal temperature. Heating curves are factory set to achieve a 22°C room temperature.
Should the temperature required differ from this, the primary temperature should be raised or lowered (offset) 3°C
for every 1°C higher or lower required as room temperature. e.g. if 20°C room temperature is required, the
primary temperature should be lowered by 6°C.
Offsetting the heating curve will change the temperature of the water in the boiler without changing the shape of
the curve. See diagram above.
To offset the curve. Press key (6) down and hold for 5 seconds to enter offset curve selection menu
The set offset in ˚C blinks in the display. Press key 6 up or down to change offset in steps of 1˚C. If there is no
pressure on the key for more than 5s shown value of offset in ˚C is saved.
Factory setting is 0˚C. Offset range is from –9 to +20˚C.
Please note that Thermal (heating) processes are slow, and the impact of alterations will not be felt immediately.
Oso recommend that adjustments are given at least 24 hours to take effect.
It is also recommended to make a log of all adjustments made and their result. This will assist in making accurate
alterations in the future.
If settings as described above are not adequate for achieving the wanted room temperature, supplemental
adjustments of the heating curves and offset can be made by the user. See table below
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 15
Conditions experienced Curve selection Offset
(radiator heating)
Offset
(UFH heating)
Room temperature is too low if the external
temperature is above + 5 oC
Lower curve by 0.1 Add with offset
+ 6 oC
Add with offset
+ 4 oC
Room temperature is too low if the external
temperature is between + 5 oC and - 5 oC
Leave the curve Add with offset
+ 3 oC
Add with offset
+ 2 oC
Room temperature is too low if the external
temperature is under - 5 oC
Higher curve by 0.1 Leave offset
0 oC
Leave offset
0 oC
Room temperature is too high if the external
temperature is above + 5 oC
Higher curve by 0.1 Lower with offset
- 6 oC
Lower with offset
- 4 oC
Room temperature is too high if the external
temperature is between + 5 oC - 5 oC
Leave the curve Lower with offset
- 3 oC
Lower with offset
- 2 oC
Room temperature is too high if the external
temperature is under- 5 oC
Lower curve by 0.1 Leave offset
0 oC
Leave offset
0 oC
5.3.4 Programmable room thermostats & setting variable internal temperatures.
Central heating is controlled by the heating curve programmed into the Termo E boiler and fine tuned by a room
thermostat.
With modern central heating controls such as a programmable room thermostat it is possible to set different room
temperatures at different times of the day. e.g. to have a lower temperature set during the night. If this system is
used the heating curve selection is unchanged and the offset of the heating curve should be set to the highest
room temperature required during the day. (See paragraph above). The programmable room thermostat is then
set according to the manufacturers instructions to set lower temperatures when required.
When setting variable temperatures please be aware that the heating system will take some time to heat up from cold and
similarly will remain hot for some time after the temperatures are reduced or the system is switched off. To optimize comfort
levels and minimize energy consumption it is suggested to activate the boiler 30 minutes before the set temperature in heating
system is required and to reduce temperature or switch off 30 minutes before the lower temperature is desired.
5.5 Protection from freezing
To protect the entire central heating system from freezing (if a building is to be left empty for an extended period
of time during cold weather), set the boiler to standby mode. The room thermostat or central heating programmer
must be set to freezing protection mode (usually 5 to 7˚C, depending from room thermostat manufacturer), this
will allow pump to circulate heated medium through central heating system.
6. Recommended annual checks (all boilers)
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).
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 16
7. Central heating controls advanced menu.
Please note that the following information provides full details on the options available for Termo boilers. In most
installations the factory settings do not require alteration.
Instructions for reading current or desired temperatures are shown in blue.
Instructions necessary for standard installations are shown in red.
Instructions necessary only for advanced programming are shown in black.
Please note that keys 6 and 8 have a rocker action and operate as directed below by up or down pressure
Display of actual primary temperature inside boiler.
Default display is of actual primary temperature inside boiler.
Display of desired primary temperature inside boiler
Press key (6) up and release to see desired primary temperature inside
boiler. (Calculated from selected heating curve)
The Display shows the desired temperature of primary water in the
boiler. The value is shown for 5 s, after which display reverts to show
actual temperature of primary water in the boiler.
Heating curve selection (ensure correct choice of radiator or
underfloor curves – see part 3.5.2 page 12)
Press key (6) up and hold for 5 seconds to enter curve selection menu.
The display blinks showing current curve setting
Values range between 1 and 3 or 0,2 and 0,8. Curves between 1 and 3
are for radiators’ central heating and curves 0,2 to 0,8 are for under floor
heating.
Press the key up or down, to alter curve selection in steps of 0,1,
according to the diagram on the front plate. If there is no pressure on the
key for more than 5 seconds the curve displayed is saved.
Limiting maximum power of boiler (manually deactivating 1 or more
immersion elements).
Press key (6) up and hold for 10 seconds to limit power level.
By pressing the key up and down it is possible to select 1 2 or 3 as
number of available power levels (immersion heaters). If there is no
pressure on key (6) for more then 5 sec. selected power level mode is
saved.
Boilers from 6 to 16 kW have only two power levels.
Limiting maximum primary temperature inside boiler (max
possible is 90°C for radiator heating and 50°C for under-
floor heating)
Press key (6) up and hold for 15 seconds to limit maximum primary
temperature inside boiler.
Factory defined maximum primary temperature starts to blink, by
pressing key (6) up or down user can set new maximum primary
temperature. If there is no pressure on key (6) for more then 5 sec.
selected maximum primary temperature is saved.
This temperature represent temperature maximum that can be
achieved regardless of selected curve.
Manual selection of desired primary temperature inside boiler
>5 sec
0.6
41
>5 sec
>10 sec
>5 sec
3
32
>5 sec
<5 sec
>15 sec
>5 sec
90
>20 sec
60
32
>5 sec
Press key (6) up and hold for 20 seconds to set primary temperature in
boiler, regardless of previously selected curve.
Desired primary temperature starts to blink. By pressing key (6) up or
down user can select fixed primary temperature in boiler. If there is no
pressure on key (6) for more then 5 sec. fixed primary temperature is
saved.
When boiler is in fixed primary temperature mode, LED display blinks
while displaying current primary temperature in boiler. For next change of
fixed temperature, user can just press key (6) up or down.
When boiler is in fixed primary temperature mode, all heating
curves are disregarded. To return to heating curve mode, boiler
must be switch OFF and back ON using ON/OFF switch.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 17
Continuation...
Display of external temperature
Press key (6) down and release to see external temperature.
The Display shows the external temperature. The value is shown for 5 s, after
which display reverts to show actual temperature of water in the boiler.
Offset of currently selected heating curve (see part 3.5.3 page 13)
Press key (6) down and hold for 5 seconds to enter offset curve selection menu
LED display will show current offset in ˚C. Offset doesn’t affect maximal or
minimal temperature, they are set in absolute values
By pressing the key (6) up or down it is possible to change offset in steps of 1˚C.
Factory setting is 0˚C.
Offset range is from –9 to +20˚C.
If there is no pressure on the key for more than 5s shown value of offset in ˚C is
saved.
Setting the minimum primary temperature inside boiler
Press key (6) down and hold for 10 seconds to select minimum primary
temperature inside boiler.
Minimum primary temperature starts to blink.
Factory setting is 45°C for radiator heating.
Factory setting is 30°C for under floor heating.
By pressing the key up or down user can select desired primary temperature in
range from 10 to 50°C. Temperature changes in 1°C steps. If there is no
pressure on the key for more than 5s the value from the display is saved as the
desired minimim primary temperature.
Displaying software version and factory reset
>5 sec
0
- 1
>5 sec
>10 sec
>5 sec
20
32
>5 sec
<5 sec
>15 sec
1.4
Press key (6) down and hold for 15 seconds, LED will show software version
and factory reset of central heating parameters will occur.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 18
8. Fault finding guide
FAULT FINDING
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 separation 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
Noise in heating pipes (Plus & PTV only) if heating circuit is small – reduce speed setting on pump.
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 19
FAULT FINDING
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
The company reserve the right to alter size, shape and specification without prior notice
TMS-UT-0804-Z01-4 page 20
RCCB switch cannot
be switched ON
Check existance
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
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
9. 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.
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