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ThermoSphere Flex Electric Combi Boiler 4–14kW – TSFLEX14, Heating + Instant Hot Water, No Flue, 7-Year Warranty
The ThermoSphere Flex Electric Combi Boiler (TSFLEX14) is a wall-mounted electric combi boiler providing both central heating and instant domestic hot water from a single self-contained unit — with no flue, no gas connection and no separate hot water cylinder. The Flex name refers to its defining capability: digitally adjustable power output from 4 to 14 kW on the heating circuit and 10 to 14 kW on the DHW circuit, set independently to match the actual heat loss of the property and avoid the wasted energy and cycling of an oversized boiler. It arrives pre-wired with 10mm² cable and pre-plumbed with an integrated pump and 5-litre expansion vessel — reducing on-site installation time significantly. Compatible with radiators, wet underfloor heating, skirting heating and external volt-free controls. At just 585 × 380 × 235mm and operating at 30 dB, it installs in the tightest spaces without noise or ventilation concerns. A 7-year warranty is available when installed with the ThermoSphere Installation Kit and registered online.
14 kW
Max Output
~100%
Efficiency
6 l/min
DHW Flow Rate
30 dB
Noise Level
585mm
Height
7 yr
Warranty (with kit)
ℹ Best Suited To: Smaller homes and flats with one bathroom and one shower — off-grid properties, flats without gas, new builds and gas boiler replacements. At 14 kW the DHW circuit delivers ~6 l/min at a 30°C rise — suitable for showers, not recommended for baths. For bath-filling properties, consider a system boiler with a hot water cylinder instead.
⚠ Hot Water Flow Rate Advisory: At maximum 14 kW output, the DHW heat exchanger delivers approximately 6 l/min at a ΔT of 30°C. ThermoSphere recommends fitting the 5 l/min Caleffi flow restrictor (included in the Installation Kit) to ensure consistent hot water temperature on the coldest days. This flow rate is not suitable for bath filling — for bath-equipped properties, a system boiler and cylinder is the correct solution.
Ideal Applications
🏠
Properties Without a Gas Supply
The Flex is the direct gas-boiler replacement for homes off the gas grid — rural properties, flats, new builds and converted outbuildings where gas connection is impractical or uneconomic.
🏢
Flats and Apartments
Wall-mounted at 585 × 380 × 235mm with no flue, it installs in kitchen cupboards and utility spaces where a gas combi would require an external wall.
🌱
Renewable Energy Integration
Pairs directly with solar PV, solar diverters and green electricity tariffs. When grid electricity is green or self-generated, the Flex is effectively zero-carbon heating.
🔧
Gas Boiler Replacement
Replaces an existing gas combi on the same pipework layout. No new flue required. The existing radiator circuit connects directly to the Flex heating ports.
Key Features & Technology
Flex — Digitally Adjustable Heating and DHW Output, 4–14 kW
The defining feature of the Flex is its digitally adjustable power output for both the heating circuit (4–14 kW) and the DHW circuit (10–14 kW) independently. A heating engineer can set the heating output to match the calculated heat loss of the property — reducing cycling, lowering running costs and extending component life. ThermoSphere recommends a minimum of 12 kW for properties with a shower and no lower than 10 kW for properties with wash-hand basins only. Output must be set by a qualified electrician.
4–14 kW heating10–14 kW DHWDigitally adjustable
Pre-Wired and Pre-Plumbed — Fast, Predictable Installation
The Flex arrives pre-wired with 10mm² supply cable and pre-plumbed with integrated pump and 5-litre expansion vessel. The heating circuit connections, pump and vessel are factory-fitted inside the casing — the installer connects mains cold water in, heating flow and return, hot water out, and the 63A electrical supply. No separate pump wiring, no separate vessel fitting. This reduces on-site time significantly compared with a system boiler and component-by-component assembly.
Pre-wired 10mm² cableIntegrated pump5L expansion vessel
Direct Hot Water — No Cylinder Required
The Flex is a combi boiler: it heats domestic hot water on demand directly from the mains cold supply, eliminating the need for a hot water storage cylinder. At 14 kW full output, the heat exchanger raises incoming cold water temperature by 30°C at 6 l/min — enough for a comfortable shower. ThermoSphere recommends fitting the 5 l/min Caleffi flow restrictor (included in the Installation Kit) to ensure consistent hot water temperature regardless of seasonal variation in incoming mains temperature.
No cylinder6 l/min at ΔT 30°C5 l/min flow restrictor recommended
Radiators, UFH and Skirting Heating — All Compatible
The heating circuit is designed to work with radiators, wet underfloor heating and skirting heating systems. Working temperature range is 30–80°C, covering both low-temperature UFH circuits (35–45°C) and conventional radiator circuits (55–75°C). Compatible with external volt-free controls — including programmers, smart thermostats and zone valves — giving the installer full flexibility to design the control system to suit the property.
RadiatorsWet UFHSkirting heatingVolt-free controls
Digital Timer and Thermostat — Integrated Controls
The boiler has an integrated digital timer and thermostat for both heating and hot water schedules. The control interface allows day-of-week and time-of-day programming directly on the unit, with up/down buttons to set each period. For more advanced control, the EPH Wireless Combi Control Pack 4 is included in the ThermoSphere Installation Kit, providing wireless room thermostat control and hot water scheduling.
Built-in timerBuilt-in thermostatEPH wireless pack in kit
~100% Efficient — Zero On-Site Emissions, No Flue
As an electric boiler, the Flex converts virtually 100% of the electrical energy drawn into useful heat — there are no flue losses, no combustion inefficiency and no standby pilot flame. Zero on-site carbon or fossil fuel emissions means no flue penetration is required, no CO detector is mandated by the boiler itself, and installation is possible on any external or internal wall. Compatible with renewable electricity sources including solar PV, wind and green tariffs.
~100% efficientNo flueZero on-site emissionsSolar compatible
Quiet Operation — 30 dB
The Flex operates at just 30 dB — quieter than a typical library. The electric heating elements have no moving parts and the integrated pump runs quietly within the sealed casing. This makes the boiler suitable for bedroom walls, under-stair cupboards and kitchen cabinets where noise from a gas boiler would be unacceptable.
30 dBNo combustion noise
Minimal Maintenance — No Annual Service Required
Unlike gas boilers, the ThermoSphere Flex has no mandatory annual service. There is no burner, heat exchanger combustion surface, flue or gas valve to inspect. Recommended periodic checks include system pressure, inhibitor levels and magnetic filter condition — all straightforward tasks. No Gas Safe engineer is required for ongoing maintenance; a competent heating engineer handles any hydraulic work.
No annual serviceNo Gas Safe required for maintenance
7-Year Warranty — with ThermoSphere Installation Kit
The Flex carries a 5-year manufacturer's warranty as standard. Install with the ThermoSphere Installation Kit and register online to extend this to 7 years total. The kit includes: WRAS-approved filling loop, Sentinel Vortex 250 magnetic filter, Sentinel X100 inhibitor, Sentinel X300 system cleaner, isolation valves (½" and ¾"), EPH Wireless Combi Control Pack 4, Caleffi 5 l/min flow valve and automatic bypass valve. ThermoSphere provides a zero-callback guarantee for registered installers — technical support is handled directly, freeing the installer after commissioning.
5-yr standard7-yr with kit + registrationZero-callback guarantee
Installation Kit — +2 Years Warranty
Install the Flex with the ThermoSphere Installation Kit and register online to extend the standard 5-year warranty to 7 years. The kit supplies all ancillary components needed for a compliant, best-practice installation including a 5 l/min flow restrictor critical for reliable DHW temperature, a magnetic filter to protect the heat exchanger, and the EPH Wireless Combi Control Pack 4 for wireless heating and hot water scheduling.
✅ 7-Year Warranty: Install with the kit + register online within 30 days of commissioning to activate the full 7-year cover.
Kit Contents
✓ WRAS-approved filling loop
✓ Sentinel Vortex 250 magnetic filter
✓ Sentinel X100 inhibitor
✓ Sentinel X300 system cleaner
✓ 2 × ½" isolation valves
✓ 2 × ¾" isolation valves
✓ EPH Wireless Combi Control Pack 4
✓ Caleffi 5 l/min flow valve
✓ Automatic bypass valve
Technical Specifications (TSFLEX14 Datasheet — 2025)
| Electrical | |
| Voltage | 230V Single Phase 50Hz |
| Recommended MCB | 63A 63A MCB |
| Recommended Cable | 10mm² 10mm² pre-wired |
| Product Code | TSFLEX14 |
| Heating Output | |
| Heating Output (Flex range) | 4 to 14 kW 4–14 kW |
| DHW Output (Flex range) | 10 to 14 kW 10–14 kW |
| Working Temperature | 30–80°C |
| Max System Pressure | 1.5 bar |
| Domestic Hot Water | |
| DHW Flow Rate | 6 l/min at 14 kW, ΔT 30°C 6 l/min |
| Recommended Flow Restriction | 5 l/min (Caleffi valve — in Installation Kit) |
| Minimum DHW Power (shower) | 12 kW |
| Minimum DHW Power (basin only) | 10 kW |
| Physical | |
| Dimensions (H × W × D) | 585 × 380 × 235 mm |
| Noise Level | 30 dB (typical) 30 dB |
| Protection Rating | IPX1 |
| Installation | Wall-mounted, indoor |
| Integrated Components | |
| Pump | Integrated (pre-plumbed) |
| Expansion Vessel | 5 litres (integrated) 5L vessel |
| Supply Cable | 10mm² pre-wired |
| Controls | Digital timer and thermostat (built-in) |
| External Controls | Volt-free terminals for external programmer / thermostat |
| Energy & Ratings | |
| Efficiency | ~100% (electric resistance heating) ~100% |
| ERP Rating — DHW | A ERP A (DHW) |
| ERP Rating — Heating | D |
| Emissions | Zero on-site carbon / fossil fuel emissions Zero on-site emissions |
| Warranty | |
| Standard Warranty | 5 years |
| Extended Warranty | 7 years — with Installation Kit + online registration 7-yr with kit |
ℹ Installation Requirements: Must be installed by a qualified heating engineer and a qualified electrician. Fill system to 1.5 bar; bleed all radiators before powering on. Flush the heating circuit to BS 7593 and add inhibitor before commissioning. Install on a sturdy, dry, well-ventilated wall — avoid locations prone to moisture build-up or extreme temperature. Confirm adequate electrical capacity at the consumer unit before ordering. Register the installation with ThermoSphere online to activate extended warranty.
Frequently Asked Questions
Related Products
ThermoSphere Micro Electric Boiler
Instant DHW only — no heating circuit, A4-sized
ThermoSphere Installation Kit
Extends warranty to 7 years; includes flow valve, filter, inhibitor & controls
Wet Underfloor Heating Kits
Pairs directly with the Flex heating circuit — 30–80°C working range
Product Information
Product Information
Shipping & Returns
Shipping & Returns
ThermoSphere Flex Electric Combi Boiler 4–14kW – TSFLEX14, Heating + Instant Hot Water, No Flue, 7-Year Warranty
ThermoSphere Flex Electric Combi Boiler 4–14kW – TSFLEX14, Heating + Instant Hot Water, No Flue, 7-Year Warranty
The ThermoSphere Flex Electric Combi Boiler (TSFLEX14) is a wall-mounted electric combi boiler providing both central heating and instant domestic hot water from a single self-contained unit — with no flue, no gas connection and no separate hot water cylinder. The Flex name refers to its defining capability: digitally adjustable power output from 4 to 14 kW on the heating circuit and 10 to 14 kW on the DHW circuit, set independently to match the actual heat loss of the property and avoid the wasted energy and cycling of an oversized boiler. It arrives pre-wired with 10mm² cable and pre-plumbed with an integrated pump and 5-litre expansion vessel — reducing on-site installation time significantly. Compatible with radiators, wet underfloor heating, skirting heating and external volt-free controls. At just 585 × 380 × 235mm and operating at 30 dB, it installs in the tightest spaces without noise or ventilation concerns. A 7-year warranty is available when installed with the ThermoSphere Installation Kit and registered online.
14 kW
Max Output
~100%
Efficiency
6 l/min
DHW Flow Rate
30 dB
Noise Level
585mm
Height
7 yr
Warranty (with kit)
ℹ Best Suited To: Smaller homes and flats with one bathroom and one shower — off-grid properties, flats without gas, new builds and gas boiler replacements. At 14 kW the DHW circuit delivers ~6 l/min at a 30°C rise — suitable for showers, not recommended for baths. For bath-filling properties, consider a system boiler with a hot water cylinder instead.
⚠ Hot Water Flow Rate Advisory: At maximum 14 kW output, the DHW heat exchanger delivers approximately 6 l/min at a ΔT of 30°C. ThermoSphere recommends fitting the 5 l/min Caleffi flow restrictor (included in the Installation Kit) to ensure consistent hot water temperature on the coldest days. This flow rate is not suitable for bath filling — for bath-equipped properties, a system boiler and cylinder is the correct solution.
Ideal Applications
🏠
Properties Without a Gas Supply
The Flex is the direct gas-boiler replacement for homes off the gas grid — rural properties, flats, new builds and converted outbuildings where gas connection is impractical or uneconomic.
🏢
Flats and Apartments
Wall-mounted at 585 × 380 × 235mm with no flue, it installs in kitchen cupboards and utility spaces where a gas combi would require an external wall.
🌱
Renewable Energy Integration
Pairs directly with solar PV, solar diverters and green electricity tariffs. When grid electricity is green or self-generated, the Flex is effectively zero-carbon heating.
🔧
Gas Boiler Replacement
Replaces an existing gas combi on the same pipework layout. No new flue required. The existing radiator circuit connects directly to the Flex heating ports.
Key Features & Technology
Flex — Digitally Adjustable Heating and DHW Output, 4–14 kW
The defining feature of the Flex is its digitally adjustable power output for both the heating circuit (4–14 kW) and the DHW circuit (10–14 kW) independently. A heating engineer can set the heating output to match the calculated heat loss of the property — reducing cycling, lowering running costs and extending component life. ThermoSphere recommends a minimum of 12 kW for properties with a shower and no lower than 10 kW for properties with wash-hand basins only. Output must be set by a qualified electrician.
4–14 kW heating10–14 kW DHWDigitally adjustable
Pre-Wired and Pre-Plumbed — Fast, Predictable Installation
The Flex arrives pre-wired with 10mm² supply cable and pre-plumbed with integrated pump and 5-litre expansion vessel. The heating circuit connections, pump and vessel are factory-fitted inside the casing — the installer connects mains cold water in, heating flow and return, hot water out, and the 63A electrical supply. No separate pump wiring, no separate vessel fitting. This reduces on-site time significantly compared with a system boiler and component-by-component assembly.
Pre-wired 10mm² cableIntegrated pump5L expansion vessel
Direct Hot Water — No Cylinder Required
The Flex is a combi boiler: it heats domestic hot water on demand directly from the mains cold supply, eliminating the need for a hot water storage cylinder. At 14 kW full output, the heat exchanger raises incoming cold water temperature by 30°C at 6 l/min — enough for a comfortable shower. ThermoSphere recommends fitting the 5 l/min Caleffi flow restrictor (included in the Installation Kit) to ensure consistent hot water temperature regardless of seasonal variation in incoming mains temperature.
No cylinder6 l/min at ΔT 30°C5 l/min flow restrictor recommended
Radiators, UFH and Skirting Heating — All Compatible
The heating circuit is designed to work with radiators, wet underfloor heating and skirting heating systems. Working temperature range is 30–80°C, covering both low-temperature UFH circuits (35–45°C) and conventional radiator circuits (55–75°C). Compatible with external volt-free controls — including programmers, smart thermostats and zone valves — giving the installer full flexibility to design the control system to suit the property.
RadiatorsWet UFHSkirting heatingVolt-free controls
Digital Timer and Thermostat — Integrated Controls
The boiler has an integrated digital timer and thermostat for both heating and hot water schedules. The control interface allows day-of-week and time-of-day programming directly on the unit, with up/down buttons to set each period. For more advanced control, the EPH Wireless Combi Control Pack 4 is included in the ThermoSphere Installation Kit, providing wireless room thermostat control and hot water scheduling.
Built-in timerBuilt-in thermostatEPH wireless pack in kit
~100% Efficient — Zero On-Site Emissions, No Flue
As an electric boiler, the Flex converts virtually 100% of the electrical energy drawn into useful heat — there are no flue losses, no combustion inefficiency and no standby pilot flame. Zero on-site carbon or fossil fuel emissions means no flue penetration is required, no CO detector is mandated by the boiler itself, and installation is possible on any external or internal wall. Compatible with renewable electricity sources including solar PV, wind and green tariffs.
~100% efficientNo flueZero on-site emissionsSolar compatible
Quiet Operation — 30 dB
The Flex operates at just 30 dB — quieter than a typical library. The electric heating elements have no moving parts and the integrated pump runs quietly within the sealed casing. This makes the boiler suitable for bedroom walls, under-stair cupboards and kitchen cabinets where noise from a gas boiler would be unacceptable.
30 dBNo combustion noise
Minimal Maintenance — No Annual Service Required
Unlike gas boilers, the ThermoSphere Flex has no mandatory annual service. There is no burner, heat exchanger combustion surface, flue or gas valve to inspect. Recommended periodic checks include system pressure, inhibitor levels and magnetic filter condition — all straightforward tasks. No Gas Safe engineer is required for ongoing maintenance; a competent heating engineer handles any hydraulic work.
No annual serviceNo Gas Safe required for maintenance
7-Year Warranty — with ThermoSphere Installation Kit
The Flex carries a 5-year manufacturer's warranty as standard. Install with the ThermoSphere Installation Kit and register online to extend this to 7 years total. The kit includes: WRAS-approved filling loop, Sentinel Vortex 250 magnetic filter, Sentinel X100 inhibitor, Sentinel X300 system cleaner, isolation valves (½" and ¾"), EPH Wireless Combi Control Pack 4, Caleffi 5 l/min flow valve and automatic bypass valve. ThermoSphere provides a zero-callback guarantee for registered installers — technical support is handled directly, freeing the installer after commissioning.
5-yr standard7-yr with kit + registrationZero-callback guarantee
Installation Kit — +2 Years Warranty
Install the Flex with the ThermoSphere Installation Kit and register online to extend the standard 5-year warranty to 7 years. The kit supplies all ancillary components needed for a compliant, best-practice installation including a 5 l/min flow restrictor critical for reliable DHW temperature, a magnetic filter to protect the heat exchanger, and the EPH Wireless Combi Control Pack 4 for wireless heating and hot water scheduling.
✅ 7-Year Warranty: Install with the kit + register online within 30 days of commissioning to activate the full 7-year cover.
Kit Contents
✓ WRAS-approved filling loop
✓ Sentinel Vortex 250 magnetic filter
✓ Sentinel X100 inhibitor
✓ Sentinel X300 system cleaner
✓ 2 × ½" isolation valves
✓ 2 × ¾" isolation valves
✓ EPH Wireless Combi Control Pack 4
✓ Caleffi 5 l/min flow valve
✓ Automatic bypass valve
Technical Specifications (TSFLEX14 Datasheet — 2025)
| Electrical | |
| Voltage | 230V Single Phase 50Hz |
| Recommended MCB | 63A 63A MCB |
| Recommended Cable | 10mm² 10mm² pre-wired |
| Product Code | TSFLEX14 |
| Heating Output | |
| Heating Output (Flex range) | 4 to 14 kW 4–14 kW |
| DHW Output (Flex range) | 10 to 14 kW 10–14 kW |
| Working Temperature | 30–80°C |
| Max System Pressure | 1.5 bar |
| Domestic Hot Water | |
| DHW Flow Rate | 6 l/min at 14 kW, ΔT 30°C 6 l/min |
| Recommended Flow Restriction | 5 l/min (Caleffi valve — in Installation Kit) |
| Minimum DHW Power (shower) | 12 kW |
| Minimum DHW Power (basin only) | 10 kW |
| Physical | |
| Dimensions (H × W × D) | 585 × 380 × 235 mm |
| Noise Level | 30 dB (typical) 30 dB |
| Protection Rating | IPX1 |
| Installation | Wall-mounted, indoor |
| Integrated Components | |
| Pump | Integrated (pre-plumbed) |
| Expansion Vessel | 5 litres (integrated) 5L vessel |
| Supply Cable | 10mm² pre-wired |
| Controls | Digital timer and thermostat (built-in) |
| External Controls | Volt-free terminals for external programmer / thermostat |
| Energy & Ratings | |
| Efficiency | ~100% (electric resistance heating) ~100% |
| ERP Rating — DHW | A ERP A (DHW) |
| ERP Rating — Heating | D |
| Emissions | Zero on-site carbon / fossil fuel emissions Zero on-site emissions |
| Warranty | |
| Standard Warranty | 5 years |
| Extended Warranty | 7 years — with Installation Kit + online registration 7-yr with kit |
ℹ Installation Requirements: Must be installed by a qualified heating engineer and a qualified electrician. Fill system to 1.5 bar; bleed all radiators before powering on. Flush the heating circuit to BS 7593 and add inhibitor before commissioning. Install on a sturdy, dry, well-ventilated wall — avoid locations prone to moisture build-up or extreme temperature. Confirm adequate electrical capacity at the consumer unit before ordering. Register the installation with ThermoSphere online to activate extended warranty.
Frequently Asked Questions
Related Products
ThermoSphere Micro Electric Boiler
Instant DHW only — no heating circuit, A4-sized
ThermoSphere Installation Kit
Extends warranty to 7 years; includes flow valve, filter, inhibitor & controls
Wet Underfloor Heating Kits
Pairs directly with the Flex heating circuit — 30–80°C working range
$623.14
Original: $2,077.15
-70%ThermoSphere Flex Electric Combi Boiler 4–14kW – TSFLEX14, Heating + Instant Hot Water, No Flue, 7-Year Warranty—
$2,077.15
$623.14Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
The ThermoSphere Flex Electric Combi Boiler (TSFLEX14) is a wall-mounted electric combi boiler providing both central heating and instant domestic hot water from a single self-contained unit — with no flue, no gas connection and no separate hot water cylinder. The Flex name refers to its defining capability: digitally adjustable power output from 4 to 14 kW on the heating circuit and 10 to 14 kW on the DHW circuit, set independently to match the actual heat loss of the property and avoid the wasted energy and cycling of an oversized boiler. It arrives pre-wired with 10mm² cable and pre-plumbed with an integrated pump and 5-litre expansion vessel — reducing on-site installation time significantly. Compatible with radiators, wet underfloor heating, skirting heating and external volt-free controls. At just 585 × 380 × 235mm and operating at 30 dB, it installs in the tightest spaces without noise or ventilation concerns. A 7-year warranty is available when installed with the ThermoSphere Installation Kit and registered online.
14 kW
Max Output
~100%
Efficiency
6 l/min
DHW Flow Rate
30 dB
Noise Level
585mm
Height
7 yr
Warranty (with kit)
ℹ Best Suited To: Smaller homes and flats with one bathroom and one shower — off-grid properties, flats without gas, new builds and gas boiler replacements. At 14 kW the DHW circuit delivers ~6 l/min at a 30°C rise — suitable for showers, not recommended for baths. For bath-filling properties, consider a system boiler with a hot water cylinder instead.
⚠ Hot Water Flow Rate Advisory: At maximum 14 kW output, the DHW heat exchanger delivers approximately 6 l/min at a ΔT of 30°C. ThermoSphere recommends fitting the 5 l/min Caleffi flow restrictor (included in the Installation Kit) to ensure consistent hot water temperature on the coldest days. This flow rate is not suitable for bath filling — for bath-equipped properties, a system boiler and cylinder is the correct solution.
Ideal Applications
🏠
Properties Without a Gas Supply
The Flex is the direct gas-boiler replacement for homes off the gas grid — rural properties, flats, new builds and converted outbuildings where gas connection is impractical or uneconomic.
🏢
Flats and Apartments
Wall-mounted at 585 × 380 × 235mm with no flue, it installs in kitchen cupboards and utility spaces where a gas combi would require an external wall.
🌱
Renewable Energy Integration
Pairs directly with solar PV, solar diverters and green electricity tariffs. When grid electricity is green or self-generated, the Flex is effectively zero-carbon heating.
🔧
Gas Boiler Replacement
Replaces an existing gas combi on the same pipework layout. No new flue required. The existing radiator circuit connects directly to the Flex heating ports.
Key Features & Technology
Flex — Digitally Adjustable Heating and DHW Output, 4–14 kW
The defining feature of the Flex is its digitally adjustable power output for both the heating circuit (4–14 kW) and the DHW circuit (10–14 kW) independently. A heating engineer can set the heating output to match the calculated heat loss of the property — reducing cycling, lowering running costs and extending component life. ThermoSphere recommends a minimum of 12 kW for properties with a shower and no lower than 10 kW for properties with wash-hand basins only. Output must be set by a qualified electrician.
4–14 kW heating10–14 kW DHWDigitally adjustable
Pre-Wired and Pre-Plumbed — Fast, Predictable Installation
The Flex arrives pre-wired with 10mm² supply cable and pre-plumbed with integrated pump and 5-litre expansion vessel. The heating circuit connections, pump and vessel are factory-fitted inside the casing — the installer connects mains cold water in, heating flow and return, hot water out, and the 63A electrical supply. No separate pump wiring, no separate vessel fitting. This reduces on-site time significantly compared with a system boiler and component-by-component assembly.
Pre-wired 10mm² cableIntegrated pump5L expansion vessel
Direct Hot Water — No Cylinder Required
The Flex is a combi boiler: it heats domestic hot water on demand directly from the mains cold supply, eliminating the need for a hot water storage cylinder. At 14 kW full output, the heat exchanger raises incoming cold water temperature by 30°C at 6 l/min — enough for a comfortable shower. ThermoSphere recommends fitting the 5 l/min Caleffi flow restrictor (included in the Installation Kit) to ensure consistent hot water temperature regardless of seasonal variation in incoming mains temperature.
No cylinder6 l/min at ΔT 30°C5 l/min flow restrictor recommended
Radiators, UFH and Skirting Heating — All Compatible
The heating circuit is designed to work with radiators, wet underfloor heating and skirting heating systems. Working temperature range is 30–80°C, covering both low-temperature UFH circuits (35–45°C) and conventional radiator circuits (55–75°C). Compatible with external volt-free controls — including programmers, smart thermostats and zone valves — giving the installer full flexibility to design the control system to suit the property.
RadiatorsWet UFHSkirting heatingVolt-free controls
Digital Timer and Thermostat — Integrated Controls
The boiler has an integrated digital timer and thermostat for both heating and hot water schedules. The control interface allows day-of-week and time-of-day programming directly on the unit, with up/down buttons to set each period. For more advanced control, the EPH Wireless Combi Control Pack 4 is included in the ThermoSphere Installation Kit, providing wireless room thermostat control and hot water scheduling.
Built-in timerBuilt-in thermostatEPH wireless pack in kit
~100% Efficient — Zero On-Site Emissions, No Flue
As an electric boiler, the Flex converts virtually 100% of the electrical energy drawn into useful heat — there are no flue losses, no combustion inefficiency and no standby pilot flame. Zero on-site carbon or fossil fuel emissions means no flue penetration is required, no CO detector is mandated by the boiler itself, and installation is possible on any external or internal wall. Compatible with renewable electricity sources including solar PV, wind and green tariffs.
~100% efficientNo flueZero on-site emissionsSolar compatible
Quiet Operation — 30 dB
The Flex operates at just 30 dB — quieter than a typical library. The electric heating elements have no moving parts and the integrated pump runs quietly within the sealed casing. This makes the boiler suitable for bedroom walls, under-stair cupboards and kitchen cabinets where noise from a gas boiler would be unacceptable.
30 dBNo combustion noise
Minimal Maintenance — No Annual Service Required
Unlike gas boilers, the ThermoSphere Flex has no mandatory annual service. There is no burner, heat exchanger combustion surface, flue or gas valve to inspect. Recommended periodic checks include system pressure, inhibitor levels and magnetic filter condition — all straightforward tasks. No Gas Safe engineer is required for ongoing maintenance; a competent heating engineer handles any hydraulic work.
No annual serviceNo Gas Safe required for maintenance
7-Year Warranty — with ThermoSphere Installation Kit
The Flex carries a 5-year manufacturer's warranty as standard. Install with the ThermoSphere Installation Kit and register online to extend this to 7 years total. The kit includes: WRAS-approved filling loop, Sentinel Vortex 250 magnetic filter, Sentinel X100 inhibitor, Sentinel X300 system cleaner, isolation valves (½" and ¾"), EPH Wireless Combi Control Pack 4, Caleffi 5 l/min flow valve and automatic bypass valve. ThermoSphere provides a zero-callback guarantee for registered installers — technical support is handled directly, freeing the installer after commissioning.
5-yr standard7-yr with kit + registrationZero-callback guarantee
Installation Kit — +2 Years Warranty
Install the Flex with the ThermoSphere Installation Kit and register online to extend the standard 5-year warranty to 7 years. The kit supplies all ancillary components needed for a compliant, best-practice installation including a 5 l/min flow restrictor critical for reliable DHW temperature, a magnetic filter to protect the heat exchanger, and the EPH Wireless Combi Control Pack 4 for wireless heating and hot water scheduling.
✅ 7-Year Warranty: Install with the kit + register online within 30 days of commissioning to activate the full 7-year cover.
Kit Contents
✓ WRAS-approved filling loop
✓ Sentinel Vortex 250 magnetic filter
✓ Sentinel X100 inhibitor
✓ Sentinel X300 system cleaner
✓ 2 × ½" isolation valves
✓ 2 × ¾" isolation valves
✓ EPH Wireless Combi Control Pack 4
✓ Caleffi 5 l/min flow valve
✓ Automatic bypass valve
Technical Specifications (TSFLEX14 Datasheet — 2025)
| Electrical | |
| Voltage | 230V Single Phase 50Hz |
| Recommended MCB | 63A 63A MCB |
| Recommended Cable | 10mm² 10mm² pre-wired |
| Product Code | TSFLEX14 |
| Heating Output | |
| Heating Output (Flex range) | 4 to 14 kW 4–14 kW |
| DHW Output (Flex range) | 10 to 14 kW 10–14 kW |
| Working Temperature | 30–80°C |
| Max System Pressure | 1.5 bar |
| Domestic Hot Water | |
| DHW Flow Rate | 6 l/min at 14 kW, ΔT 30°C 6 l/min |
| Recommended Flow Restriction | 5 l/min (Caleffi valve — in Installation Kit) |
| Minimum DHW Power (shower) | 12 kW |
| Minimum DHW Power (basin only) | 10 kW |
| Physical | |
| Dimensions (H × W × D) | 585 × 380 × 235 mm |
| Noise Level | 30 dB (typical) 30 dB |
| Protection Rating | IPX1 |
| Installation | Wall-mounted, indoor |
| Integrated Components | |
| Pump | Integrated (pre-plumbed) |
| Expansion Vessel | 5 litres (integrated) 5L vessel |
| Supply Cable | 10mm² pre-wired |
| Controls | Digital timer and thermostat (built-in) |
| External Controls | Volt-free terminals for external programmer / thermostat |
| Energy & Ratings | |
| Efficiency | ~100% (electric resistance heating) ~100% |
| ERP Rating — DHW | A ERP A (DHW) |
| ERP Rating — Heating | D |
| Emissions | Zero on-site carbon / fossil fuel emissions Zero on-site emissions |
| Warranty | |
| Standard Warranty | 5 years |
| Extended Warranty | 7 years — with Installation Kit + online registration 7-yr with kit |
ℹ Installation Requirements: Must be installed by a qualified heating engineer and a qualified electrician. Fill system to 1.5 bar; bleed all radiators before powering on. Flush the heating circuit to BS 7593 and add inhibitor before commissioning. Install on a sturdy, dry, well-ventilated wall — avoid locations prone to moisture build-up or extreme temperature. Confirm adequate electrical capacity at the consumer unit before ordering. Register the installation with ThermoSphere online to activate extended warranty.
Frequently Asked Questions
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