The Strom 24kW Electric Combi Boiler (three-phase, model SBTP24C) is the range-topping combi in Strom's electric boiler line-up, combining central heating and instant hot water in one compact, flue-free unit. Running on a 400V three-phase supply, its 24kW output is intended for larger properties or higher-demand applications such as multiple bathrooms and back-to-back showers, where a smaller electric combi wouldn't keep up.
Built around Strom's patented serpentine heat exchanger for fast, even heat transfer, the SBTP24C pairs a full-colour touchscreen interface with an integrated pump and expansion vessel, running at over 99% efficiency with zero carbon monoxide emissions at the point of use. It suits off-grid homes, flats, and properties transitioning away from gas or oil, particularly where a three-phase electrical supply is already available.
24 kW
Heat Output
400V 3PH
Power Supply
36 A
Rated Current
99%+
Efficiency
IPX4
Protection Class
2 Yr
Warranty*
Qualified Electrician & Plumber Required
Installation must be carried out by a qualified electrician and plumber in accordance with BS 7671 wiring regulations and current building regulations. An electrical installation certificate and Part P certificate are legally required for the new circuit, and are also a condition of the manufacturer's warranty.
Three-Phase Supply Required
This model requires a three-phase 400V electrical supply. Where only single-phase power is available, Strom's single-phase system and combi boilers (up to 14.4kW) should be considered instead. Actual delivered hot water flow rate also depends on incoming mains water pressure, so this should be checked alongside the electrical supply before ordering.
Correct Sizing Matters
A proper heat loss calculation should be carried out before purchase. Electric boilers are 100% efficient at the point of use, so replacing an older gas or oil boiler like-for-like will typically oversize the new unit, which Part L 2022 of the Building Regulations advises against.
Combi Design, No Cylinder Needed
Heating and instant hot water from one compact unit, removing the need for a separate hot water cylinder and freeing up airing cupboard or plant room space.
Patented Serpentine Heat Exchanger
Heat spreads evenly across the whole element surface rather than at a single hotspot, improving heat-up speed and reducing limescale-related performance loss over time.
Full-Colour Touchscreen Interface
An intuitive touchscreen gives precise control over flow temperature and system status, simplifying day-to-day operation for the end user.
Integrated Pump & Expansion Vessel
The circulation pump and expansion vessel are built in, simplifying installation and reducing the number of separate parts to source and fit.
Highest Output in the Combi Range
At 24kW, this is the largest Strom electric combi available, suited to properties with the greatest simultaneous heating and hot water demand.
Solar & Economy Tariff Compatible
Works alongside solar PV systems and is well suited to Economy 10 and similar time-of-use electricity tariffs to help manage running costs.
General
Model / MPN
SBTP24C
Boiler Type
Electric Combi Boiler (heating & instant hot water)
Heating Output
24 kW
Heating Element
Patented multi-strand serpentine heat exchanger
Efficiency
99%+, zero carbon monoxide at point of use
Protection Class
IPX4
Electrical Supply
Phase
Three-phase
Voltage
400V AC
Rated Current
36 A
Minimum Recommended Breaker
40 A
Minimum Recommended Cable Size
3 x 6mm²
Heating & Hot Water Circuit
Max. Heating Pressure
1.5 bar
DHW Flow Rate Note
Limited by incoming mains supply; three-phase supply recommended for bath filling
Max. Flow Temperature
Suitable for domestic hot water and central heating
Physical & Compliance
Dimensions (H x W x D)
700 x 425 x 260mm
Weight
29.1 kg
Mounting
Wall-mounted, no flue required
Warranty
2-year manufacturer warranty (extendable to 24 months upon registration)
Compatible With
Solar panels, Economy 10 tariffs, most UK domestic heating systems
Does this boiler need a flue or gas connection?
No. The SBTP24C is fully electric with no flue, no gas supply and no carbon monoxide risk at the point of use, making it suitable for off-grid homes, flats, or properties where a flue can't be fitted.
What electrical supply does this boiler need?
A three-phase 400V supply drawing 36A, with a minimum 40A breaker and 3 x 6mm² cable recommended; an electrician should always confirm this against the property's actual supply and load.
How does this compare to the 21kW combi model?
The SBTP24C is the largest Strom combi available, suited to properties with the highest simultaneous heating and hot water demand. A heat loss and hot water demand calculation should confirm whether the smaller 21kW model would be sufficient, since Strom advise against oversizing.
Can it also run underfloor heating?
Yes, the boiler is compatible with underfloor heating systems as well as standard radiator central heating circuits.
Can it work with solar panels?
Yes, it is compatible with solar PV systems and Economy 10-style tariffs to help reduce running costs.
Who can install this boiler?
Installation must be carried out by a qualified electrician and plumber in accordance with BS 7671 and current UK building regulations, with full electrical and plumbing checks completed before use.
