ThermoSphere Electric Heat Only Boiler (4.5kW-15kW)

Description

The ThermoSphere Electric Heat Only Boiler is a wall-mounted electric boiler designed to heat water for central heating radiators, wet underfloor heating circuits, and domestic hot water via an indirect cylinder coil. Built around a cluster of resistive heating elements housed in an insulated steel cylinder, it delivers a 99.8% efficient heat source with no flue gas emissions and no fossil fuel burned on site.

It is the natural alternative to a gas or oil boiler for properties without a gas supply, or where flue routing and space are at a premium. The range spans 4.5kW to 15kW across five models, all sharing the same compact wall-mounted casing, plumbing layout and control logic — so sizing is simply a matter of matching output to heating/hot water demand.

4.5-15kW

Output Range

99.8%

Efficiency

230/400V

Supply Options

65°C

Max Temperature

IP22

Protection Rating

5 Years

Warranty

Good to Know

Works with standard radiators, programmers, thermostats and thermostatic radiator valves, and can be plumbed into an indirect hot water cylinder to provide domestic hot water alongside space heating — making it a straightforward drop-in for existing wet heating systems.

Important Safety Information

This appliance must only be installed and maintained by a qualified, competent professional. It must be safely earthed at all times, fed from a dedicated, suitably rated supply circuit with provision for safe electrical isolation, and the boiler must never be energised before the plumbing circuit is filled and pressurised. Models up to and including 12kW can run on single-phase (230V) or three-phase (400V) supply; the 15kW model is three-phase (400V) only.

Zero On-Site Emissions

With 99.8% efficiency and no flue gas emissions, the boiler removes the need for any flue routing, making it ideal for flats, outbuildings or renovations where running a flue is impractical or impossible.

Resistive Element Cluster Design

Heat is generated by a cluster of resistive heating elements housed inside an insulated steel cylinder, with cold water entering at the base and heated water leaving via the top flow connection.

Single or Three-Phase Flexibility

Models from 4.5kW to 12kW can be wired for single-phase (230V) or three-phase (400V) supply by removing a jumper clip on the live terminals, giving installers flexibility based on the property's existing supply.

Built-In Control Circuit Supply

A 3 Amp fused control circuit supply is built into the boiler, removing the need for a separate fused spur when wiring in external thermostats or programmers.

Dual Safety Cut-Out Protection

A thermal cut-out switch isolates the heating elements above 80°C, while the internal 3 Amp control circuit fuse protects the low-voltage control wiring.

Compact Wall-Mounted Footprint

At just 220mm × 575mm × 115mm, the boiler mounts directly to a load-bearing wall with 500mm clearance recommended on all sides for safe access and servicing.

General
Dimensions (W×H×D)	220mm × 575mm × 115mm
Max working temperature	65°C
Max working pressure	2.0 BAR (rated system pressure 0.5-2 BAR; 1.5 BAR recommended)
Protection rating	IP22
IEC protection	Class I
Efficiency	99.8%, zero flue gas emissions
Warranty	5 years
Safety & Control
Thermal cut-out	Isolates elements above 80°C
Control circuit fuse	Internal 3 Amp fuse
Control circuit supply	3 Amp, built-in (no separate fused spur required)
Compatible controls	External room/cylinder thermostats, programmers, TRVs, S Plan/Y Plan
Plumbing connections	3/4" BSP flow and return
Earthing	Must be permanently earthed to mains earth

Code	Output	Output per Element	Voltage	Current	Weight	EAN
TSEFB-4.5	4.5kW	1.5kW	230/400V	21A	13kg	5056257307954
TSEFB-6	6.0kW	2.0kW	230/400V	27A	13kg	5056257307961
TSEFB-9	9.0kW	3.0kW	230/400V	40A	13kg	5056257307978
TSEFB-12	12.0kW	4.0kW	230/400V	53A	13kg	5056257307985
TSEFB-15	15.0kW	5.0kW	400V	22A	13kg	5056257307992

The manufacturer's data sheet lists maximum working pressure as 2.0 BAR, while the installation manual states the safe operating range as 0.5-2 BAR, with 1.5 BAR recommended.

Can this boiler provide domestic hot water as well as heating?

Yes. When plumbed into an indirect hot water storage cylinder, the boiler can provide both central heating and domestic hot water from the same unit.

Does the 15kW model work on a single-phase supply?

No. The TSEFB-15 is 400V three-phase only. Models from 4.5kW to 12kW can run on either single-phase (230V) or three-phase (400V) supply.

Do I need a separate fused spur for room thermostats or programmers?

No. The boiler includes a built-in 3 Amp fused control circuit supply, so external controls can be powered directly from the boiler.

What size circuit breaker do I need?

The circuit breaker must be rated higher than the maximum current draw of the chosen model — for example, a boiler drawing 21A should be protected by at minimum a 25A MCB. Always confirm sizing with a qualified electrician.

Can this boiler be installed without a flue?

Yes. As an electric resistive-element boiler, it produces no flue gases and requires no flue, making it suitable for properties without gas or where flue routing isn't possible.

What is the warranty on this boiler?

Each unit carries a 5-year warranty from Thermogroup Ltd, subject to installation by a qualified professional in accordance with the ThermoSphere instructions.

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Room Dimensions

Length (in m):

Width (in m):

Height (in m):

Room Type

Living Room

Bedroom

Kitchen

Bathroom

Conservatory

Hallway

Glazing Type

Single Glazed

Double Glazed

Triple Glazed

External Walls

0 Wall

1 Wall

2 Walls

3 Walls

4 Walls

Insulation Level

Poor

Average

Good (New Build)

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