The Strom 14.4 kW Single Phase Heat Only Electric Boiler (SBSP15H) is the highest-output model in the Strom single-phase heat-only range, designed to serve larger homes or properties where a separate indirect hot water cylinder already handles domestic hot water. At just 520 × 235 × 120 mm and drawing 62 A from a standard 230 V single-phase supply, it delivers 14.4 kW of continuous central heating output from a unit smaller than most gas boilers. The heat-only format means there is no integrated pump or expansion vessel — these are fitted externally, giving the installer complete control over component selection and positioning. No flue is required, zero CO or CO₂ emissions at point of use, and with almost no moving parts the boiler runs near-silently throughout its service life. Compatible with solar PV diversion, underfloor heating and all standard S-plan and Y-plan central heating systems. LED digital display. 2-year manufacturer’s warranty with registration within 45 days (1 year without).

14.4 kW

Heat output

230V 1 ph

Single phase

62A

Current draw

No flue

Zero CO emissions

20– 80°C

Flow temp range

2 yr

Warranty (registered)

⚠ Professional installation required: This boiler draws 62 A at 230 V and must be connected to the mains by a competent electrician certified to BS 7671 (18th Edition). Plumbing installation must be completed by a qualified and certified heating engineer. Strom Limited accepts no liability for installations carried out by unqualified persons.

ℹ Register within 45 days for the full 2-year warranty: The standard out-of-box warranty is 1 year. Register at stromltd.com/guarantee within 45 days of purchase using the registration card supplied in the box to extend this to 2 years. Only the legal owner of the building can register and make a warranty claim. Keep your merchant invoice as proof of purchase.

ℹ External components required — not included: The heat-only boiler does not include a pump, expansion vessel or filling loop. These must be installed externally by a qualified engineer. An external bypass valve must also be fitted to allow system circulation when all TRVs are closed. Flexi hoses are strongly recommended on the flow and return connections.

What’s in the Box

Strom SBSP15H Boiler Unit

14.4 kW wall-mounted heat-only electric boiler. Built-in auto air vent, LED digital display and 15 mm compression PRV connection. Upright installation only.

Wall Fixings and Mounting Guide

All fixings for wall installation. Wall must support the boiler’s weight when filled. Boiler must be mounted vertically — other orientations void the warranty.

Installation Manual

Strom installation and operating instructions: system design, electrical connection, commissioning and maintenance requirements.

Warranty Registration Card

Register at stromltd.com/guarantee within 45 days of purchase to activate the 2-year warranty. Keep your invoice as proof of purchase.

Heat Only vs System Boiler — Which Do You Need?

	Heat Only (this boiler)	System Boiler
Integrated pump	✘ External (installer’s choice)	✓ Built-in
Integrated expansion vessel	✘ External (installer’s choice)	✓ Built-in
Domestic hot water	✘ Indirect cylinder required	✘ Indirect cylinder required
Physical size	Smallest (520 × 235 × 120mm)	Larger (includes pump and vessel)
Best for	Existing systems with external components; tight spaces; maximum flexibility	New installations wanting all-in-one unit
Bypass valve required	✓ Yes (external)	✓ Yes (external)

Both types require an indirect hot water cylinder for domestic hot water. Choose the heat-only format when an external pump and vessel are already in place, when space is extremely tight, or when the installer needs to specify their own pump grade.

External Components Required — Not Included

The heat-only format contains only the heating element, controls and safety devices. Your heating engineer will need to supply and fit the following:

Circulator Pump (required)

Circulates heated water around the system. Use a high-efficiency variable-speed pump. Full bore isolation valves only on flow and return — standard ball valves restrict flow and reduce performance.

Expansion Vessel (required)

Accommodates thermal expansion of heating water. Size to suit total system volume. Must be pre-charged to match system fill pressure before commissioning.

Bypass Valve (required)

Allows system water to circulate when all TRVs are fully closed. Prevents the boiler from overheating under low-demand conditions.

Filling Loop (required)

For pressurising the system to 1.0 – 1.5 bar at commissioning. Must be removed after filling per Water Supply (Water Fittings) Regulations.

Full Bore Isolation Valves (strongly recommended)

Fit on flow and return to isolate the boiler for maintenance without draining the whole system. Standard ball valves create flow restrictions; full bore valves do not.

Flexi Hoses (strongly recommended)

Strom recommends flexi hoses on the 3/4" flow and return connections. Overtightening rigid compression fittings can damage boiler internals — this is explicitly excluded from warranty cover.

Key Features

14.4 kW — Maximum Single-Phase Heat-Only Output

This is the highest output available from a 230 V single-phase heat-only electric boiler. A typical UK three-bedroom semi-detached has a design heat load of 6 – 9 kW; larger or poorly insulated properties can reach 12 – 14 kW. At 14.4 kW this boiler covers the full single-phase residential range. Properties needing more than 14.4 kW would require a three-phase supply.

14.4 kW230V single phase62A / min 63A breaker

Smallest Possible Unit — 520 × 235 × 120 mm

Stripping out the pump and vessel leaves a unit roughly the size of a large hardback book. The 120 mm depth is less than many kitchen cupboard shelves. The SBSP15H fits inside a kitchen cabinet, on an airing cupboard wall, in a utility room corner, in a garage, or in any plant room with minimal clear wall space. It must be mounted upright on a vertical wall — any other orientation invalidates the warranty.

520 × 235 × 120mmUpright wall mount only

No Flue, No Gas, No Emissions at Point of Use

With no burner, no combustion and no exhaust gas, no flue is required and there is zero risk of carbon monoxide. This eliminates the structural and regulatory complexity of gas or oil installation and makes the boiler suitable for any indoor location without ventilation requirements. Ideal for off-gas-grid properties, flats where fluing is impractical, and heritage or listed buildings where external penetrations are restricted.

No flueZero CO riskOff-gas-grid compatible

LED Digital Display — External Thermostat Compatible

The LED digital display shows flow temperature and system status. Temperature is adjustable across the full 20 – 80°C range. An external room thermostat or time clock can be wired in for zone control and scheduling — compatible with standard S-plan, Y-plan and wiring centre configurations.

LED display20–80°CExternal thermostat compatible

Solar PV Diversion and Underfloor Heating Compatible

Works with solar PV diversion devices (myenergi Eddi, iBoost, etc.) to use surplus solar generation for space heating instead of exporting at low SEG rates. The 20 – 80°C flow temperature range also makes it compatible with wet underfloor heating systems, which typically operate at 35 – 55°C (use manifold mixing valves to maintain correct UFH temperatures).

Solar PV diversionUnderfloor heating20–80°C range

Near-Silent Operation — Minimal Moving Parts

No burner, no fan, no heat exchanger, no internal pump. The heating element operates in complete silence. The only sound in the system comes from the external pump, which the installer can position to minimise noise transmission. Minimal moving parts means fewer wear components, lower servicing requirements and high long-term reliability.

No burner or fanNear-silentLow servicing requirement

Built-in Auto Air Vent and PRV Connection

An automatic air vent is built into the boiler. If used with an indirect cylinder, an additional auto air vent should be fitted near the cylinder coil. The 15 mm compression PRV connection accepts the pressure relief valve, which must be piped to a safe discharge point. A system drain point should be fitted at the lowest point of the circuit to allow draining without discharging through the PRV.

Built-in auto air vent15mm compression PRV connection

All Standard Heating Configurations Supported

Compatible with S-plan, Y-plan, fully pumped and gravity-assisted systems. Supplies a heating circuit and can feed an indirect hot water cylinder via a motorised valve or cylinder thermostat. System design to BS EN 12828 / 12831. Water treatment to BS EN 7593 with a proprietary inhibitor to protect the heating element and pipework.

S-plan and Y-planSealed systemIndirect cylinder

Installation Quick Reference

Electrical supply

230 V single phase. 62 A draw. Min 63 A circuit breaker. Min 10 mm² cable. Linked isolator with min 3 mm contact gap in every pole. Cable entry at top right panel.

Electrical certification

Connection by a competent electrician to BS 7671 (18th Edition). System must be earthed before any current is applied.

Plumbing certification

By a qualified and certified heating engineer. Design to BS EN 12828, 12831 and 14336. Water treatment to BS EN 7593.

System pressure

Fill to 1.0 – 1.5 bar. Fill slowly, vent all manual release valves to purge air. Remove filling loop after commissioning.

Pipework connections

3/4" male (22 mm pipe). Full bore isolation valves on flow and return. Flexi hoses strongly recommended. Do not overtighten rigid fittings.

Mounting and location

Upright on vertical wall only — other orientations void warranty. Wall must support boiler weight when filled. Allow access for front panel removal. Avoid frost-risk locations.

Technical Specifications

Boiler Performance
Model	SBSP15H
Heat output	14.4 kW
ERP rating (heating)	D
Flow temperature range	20 – 80°C (adjustable)
Heating pressure range	0.5 – 1.5 bar
Electrical
Power supply	230 V, single phase
Current draw	62 A
Minimum circuit breaker	63 A
Minimum cable size	10 mm²
Connections
Flow and return	3/4" Male (22 mm pipe)
PRV connection	15 mm compression
Physical
Dimensions (H × W × D)	520 × 235 × 120 mm
Mounting	Wall-mounted, upright only (warranty void otherwise)
Features
Display	LED digital display
Built-in auto air vent	Yes
Integrated pump	No — external pump required
Integrated expansion vessel	No — external expansion vessel required
Flue required	No
Emissions at point of use	Zero (no combustion)
Compatibility
Heating systems	S-plan, Y-plan, sealed system, fully pumped
Domestic hot water	Via indirect cylinder (sold separately)
Solar PV diversion	Compatible
Underfloor heating	Compatible
Standards
Heating design	BS EN 12828, BS EN 12831, BS EN 14336
Electrical	BS 7671 (18th Edition IEE Wiring Regulations)
Water treatment	BS EN 7593
Warranty
Standard warranty	1 year (without registration)
Extended warranty	2 years (register within 45 days at stromltd.com/guarantee)
Warranty holder	Legal owner of building only
Box Contents
Included	Boiler unit, wall fixings, mounting guide, installation manual, registration card
EAN barcode	5060438333571

Frequently Asked Questions

What is the difference between a heat-only and a system electric boiler?

A heat-only boiler contains only the heating element, controls and safety components. There is no pump or expansion vessel. These are installed externally by the engineer, who chooses their specification and positioning. A system boiler includes both components in a larger housing. The heat-only format is the better choice for existing systems that already have an external pump and vessel, for installations where space is extremely tight, or where the engineer wants full control over component selection.

What size indirect cylinder does this boiler need?

The cylinder size depends on the property’s daily hot water demand, not the boiler output. General UK guidance: 1 – 2 people = 120 – 150 litres; 3 – 4 people = 150 – 210 litres; 5+ people = 250 – 300 litres. At 14.4 kW the boiler will heat a 150 litre cylinder from cold to 60°C in approximately 30 minutes. Your heating engineer should complete a full heat loss and cylinder sizing calculation.

Does this boiler work with Economy 7 or Economy 10 tariffs?

Yes. The SBSP15H can be controlled via external time clocks or a room thermostat, allowing it to be scheduled to run during off-peak tariff periods. On Economy 7 or Economy 10, the boiler can heat the property and charge the hot water cylinder overnight at reduced electricity rates. Pairing with a solar PV array and diversion device can further reduce daytime grid import by directing surplus solar generation to heating.

Why does Strom recommend flexi hoses rather than rigid fittings?

The 3/4" male connections on the boiler require tightening to form a watertight seal. The force applied to rigid compression or push-fit fittings can be transmitted to the boiler’s internal connections, potentially damaging the element housing. Flexi hoses absorb this mechanical stress and accommodate minor misalignment. Strom’s installation manual explicitly states that damage from overtightening rigid fittings is not covered under warranty.

Why must I use full bore isolation valves rather than standard ball valves?

Standard ball valves have a reduced bore that creates a flow restriction when open. Immediately adjacent to the boiler, this limits circulation rates and can cause localised overheating of the heating element. Full bore isolation valves have the same internal diameter as the connected pipework and create no restriction, maintaining correct flow and protecting long-term performance.

Is this boiler suitable for a property off the gas grid?

Yes — this is one of the SBSP15H’s primary use cases. Properties that cannot access mains gas, where an LPG installation is impractical, or where fluing is restricted (listed buildings, upper-floor flats) are well served by an electric boiler. The running cost per kWh is higher than gas, but this can be offset by pairing with a solar PV system and/or battery storage, and by taking advantage of Economy 7 or Economy 10 off-peak tariffs to heat the property and charge hot water storage at lower electricity rates.

Heat Only Electric Boilers | For Open-Vented & Gravity-Fed Heating Systems