The Strom 18kW Electric Combi Boiler (three-phase, model SBTP18C) delivers both central heating and instant domestic hot water from a single unit, with no separate hot water cylinder or gas connection needed. Running on a standard 400V three-phase supply, it produces up to 9 litres per minute of hot water at a 30°C temperature rise, suiting larger family homes with two to four bathrooms or properties with genuinely high simultaneous hot water demand.
Built around Strom's patented serpentine heat exchanger, which spreads heat evenly across the whole element rather than at a single hotspot, the SBTP18C combines a touchscreen control panel with LED display, an integrated pump and expansion vessel, and near-silent operation at just 15dB. With no flue, no gas supply and zero carbon monoxide risk, it's a practical, space-saving replacement for a gas or oil combi in homes already wired for three-phase power.
18 kW
Heat Output
9 L/min
DHW Flow @ 30°C Rise
400V 3PH
Power Supply
26 A
Current Per Phase
15 dB
Sound Pressure
5 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.
Check Mains Flow Rate Before Buying
The 9 litres/minute DHW figure is the boiler's maximum output at a 30°C temperature rise; the actual hot water flow rate delivered depends on the incoming mains water pressure and flow. Strom recommend sizing by heating demand first and then checking that the mains flow rate is adequate, since an electric combi may not suit every property's water supply.
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.
Near-Silent 15dB Operation
With minimal moving parts, the boiler runs quietly enough to be installed close to living areas or bedrooms without disturbance.
Touchscreen & LED Display
A full touchscreen interface gives precise control over flow temperature, timer settings and live system status at a glance.
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.
Solar & Economy Tariff Compatible
Works alongside a solar PV diverter to use surplus generation for water heating, and is well suited to Economy 10 and similar time-of-use electricity tariffs.
General
Model / MPN
SBTP18C
EAN
5060797570044
Boiler Type
Electric Combi Boiler (heating & instant hot water)
Heating Output
18 kW
Heating Element
Patented multi-strand serpentine heat exchanger
Sound Pressure Level
15 dB (near-silent operation)
Electrical Supply
Phase
Three-phase
Voltage
400V AC
Current Draw
26 A per phase
Minimum Recommended Breaker
32 A per phase
Minimum Recommended Cable Size
6mm² per phase
Heating & Hot Water Circuit
Max. Heating Pressure
1.5 bar
Min. Heating Pressure
0.5 bar
Max. DHW Pressure
6.0 bar
DHW Flow Rate (30°C Rise)
9 litres/minute
Max. Flow Temperature
80°C
Heating Connection
3/4" Male
DHW Connection
1/2" Male
PRV Connection
1/2" Female
Physical & Compliance
Dimensions (H x W x D)
700 x 425 x 260mm
Weight
20 kg
Mounting
Wall-mounted, integrated bracket, upright position only
ErP Rating (Heating / DHW)
D / A
Compatible With
Solar PV diverters, underfloor heating, Economy 10 tariffs
Does this boiler need a flue or gas connection?
No. The SBTP18C is 100% electric with no flue, no gas supply and no carbon monoxide risk, making it safe to install in almost any property, including new-builds and urban retrofits.
How much hot water can it supply?
Up to 9 litres per minute at a 30°C temperature rise, suiting larger family homes or properties with two to four bathrooms and higher simultaneous hot water demand.
Can it work with solar panels?
Yes, when paired with a solar PV diverter it can use surplus solar generation to help heat water, reducing running costs alongside compatible time-of-use electricity tariffs.
How quiet is the boiler in operation?
Very quiet: Strom quote a 15dB sound pressure level, making it suitable for installation near living areas or bedrooms.
What electrical supply does it need?
A three-phase 400V supply drawing 26A per phase, with a minimum 32A breaker per phase and 6mm² cable per phase recommended; an electrician should always confirm this against the property's actual supply.
Can it also run underfloor heating?
Yes, the boiler's maximum flow temperature of 80°C is compatible with underfloor heating systems, which typically run at lower flow temperatures than radiators for efficient operation.
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.
