The Strom 9kW Electric Heat-Only Boiler with 150L Pre-Plumbed Indirect Cylinder (SKU: SBSP9H150PP) is a complete, factory-assembled one-box heating and hot water system for properties without a mains gas connection. The 9kW single-phase electric boiler arrives pre-mounted on the outside of the 150L duplex stainless steel unvented cylinder, with the expansion vessel, circulator pump, pressure gauge, filling loop and safety controls all factory-fitted. On site, only the flow, return, cold supply and electrical connections need to be made — no boiler assembly, no pump or vessel mounting, no guesswork. The cylinder uses Strom's Prime2o duplex stainless steel construction, with 50mm insulation and a coil rated at 19.94 kW for fast indirect heat-up from the boiler circuit. Backed by a 25-year manufacturing guarantee on the cylinder and a 2-year warranty on the boiler (registration within 45 days required). Suitable for: 2–3 bedroom property (well-insulated semi or end-terrace).
9kW
Heat Output
150L
Cylinder
25 yr
Cyl Guarantee
2 yr
Boiler Warranty
10 bar
Max Pressure
No Flue
Required
⚠ G3 & Electrician Required: The cylinder is unvented (pressurised). Installation must be carried out by a G3 Competent Person for the cylinder and a qualified electrician for the boiler wiring. Building Regulations Part G applies.
⚠ Boiler Warranty Registration: The 2-year boiler warranty must be registered within 45 days of purchase at stromltd.com. Retain the invoice as proof of purchase.
Key Features
One-Box System — Boiler and Cylinder Factory-Mounted Together
The 9kWkW heat-only boiler is mounted directly onto the outside of the 150L pre-plumbed cylinder before despatch, arriving as a single ready-to-position unit. Expansion vessel, circulator pump, pressure gauge, filling loop and safety controls are all pre-fitted — only the flow, return, cold water and electrical connections need to be made on site.
The cylinder is manufactured from duplex stainless steel — the same alloy grade used in marine and chemical processing applications for its superior resistance to corrosion and stress cracking. Strom backs it with a 25-year manufacturing guarantee. 50mm PU foam insulation minimises standby heat loss for efficient round-the-clock performance. Rated to 10 bar maximum working pressure and 3 bar fill pressure.
Duplex stainless steel25-yr cylinder guarantee10 bar rated
Serpentine Heating Element Technology — Efficient and Reliable
The boiler uses Serpentine heating element technology — a continuous wound element with a larger heat-transfer surface area than dry-core or standard sheathed elements. This means more efficient heat transfer to the system water, lower surface temperature per watt, and extended element life compared with conventional designs.
Serpentine elementHigh heat transferLong element life
Touchscreen Control Display — Simple On-Site Commissioning
The boiler features a touchscreen control panel with backlit display. Flow temperature is adjustable from 20°C to 80°C in 1°C steps. The display shows current flow temperature, set-point, fault codes and system pressure at a glance. No separate programmer is included — the boiler integrates with standard wiring centres, room thermostats and zone valves.
Touchscreen20–80°C rangeFault code display
No Flue, No Gas, No Carbon Monoxide — Safe for Any Location
As a fully electric system, the Strom boiler requires no flue, no gas supply and produces no carbon monoxide. It can be sited in cupboards, utility rooms or any location where a gas or oil boiler would not be permitted or practical. Ideal for off-grid properties, flats, conversions and commercial premises without a mains gas connection.
No flue neededNo gas supplyZero CO outputOff-grid ready
Solar Panel Compatible — Reduce Running Costs with PV
The boiler is compatible with solar PV panels via an appropriate solar diverter (such as Solar iBoost+ or myenergi eddi). Surplus solar generation can be diverted to heat the cylinder immersion, substantially reducing electricity running costs. The pre-plumbed cylinder includes a single immersion heater boss for direct electric top-up.
Solar PV compatibleImmersion boss includedDiverter-ready
Heating Pressure Range: 0.5–1.5 Bar — Standard Sealed System
The boiler operates within a 0.5 to 1.5 bar sealed heating circuit pressure range. The pre-fitted expansion vessel accommodates normal system expansion. A pressure relief valve and filling loop are included. System pressure is displayed on the touchscreen — no separate pressure gauge dial to read.
0.5–1.5 bar working pressurePRV + filling loop includedExpansion vessel pre-fitted
Qualified Installation Required — G3 Competent Person + Qualified Electrician
The cylinder is unvented (pressurised) and must be installed by a G3 Unvented Competent Person in accordance with Building Regulations Part G. The boiler wiring must be carried out by a qualified electrician to BS 7671. Strom recommend a dedicated RCD-protected circuit for the boiler. Boiler warranty requires registration within 45 days of purchase at stromltd.com.
G3 competent personQualified electricianRegister within 45 days
Technical Specifications
Boiler
Heat Output
9kW
Power Supply
230V, single phase
Current Draw
41A
Minimum Breaker Size
50A
Minimum Cable Size
6 mm²
Heating Temperature Range
20°C – 80°C
Heating Pressure Range
0.5 – 1.5 bar
Flow & Return Connection
¾" male (flexi hoses or push-fit recommended)
PRV Connection
15mm compression
Boiler Dimensions (H×W×D)
520 × 235 × 120 mm
Controls
Touchscreen with display
ERP Rating (Heating)
D
Cylinder
Cylinder Type
Pre-plumbed indirect unvented (Prime2o)
Nominal Capacity
150L
Actual Capacity
147 litres
Cylinder Material
Duplex stainless steel
Insulation
50mm PU foam
Weight Empty
48 kg
Weight Full
196 kg
Heat Loss
1.32 kWh/24h
Coil Rating
19.94 kW
Max Water Pressure
10 bar
Max Fill Pressure
3 bar
Number of Immersions
1
Cylinder Dimensions (H×W×D)
1075 × 580 × 660 mm
ERP Rating (Cylinder Only)
C
Compatibility & Warranty
Heating Type
Heat-only (regular boiler) — requires separate system controls (programmer, room stat, zone valves)
Solar PV Compatible
Yes — via solar diverter to immersion
SKU / Part Number
SBSP9H150PP
Boiler Warranty
2 years (registration within 45 days at stromltd.com)
Cylinder Guarantee
25-year manufacturing guarantee
Manufacturer
Strom Ltd, UK
Frequently Asked Questions
What electrical supply does the 9kWkW boiler require?
A 230V single-phase supply is required. The 9kWkW boiler draws 41AA at full load. Minimum MCB/RCB size: 50AA. Minimum cable size: 6 mm². Calculations should always be verified for the specific installation, as local voltage and cable run length affect the correct breaker and cable size. Wiring must be carried out by a qualified electrician to BS 7671.
Does this unit need a flue or gas connection?
No. The Strom 9kWkW is a fully electric boiler — it requires no flue, no gas supply and produces no carbon monoxide. It can be installed in any indoor location that meets the electrical supply and physical access requirements, including airing cupboards, utility rooms and plant rooms.
Who can install this unit?
The unvented cylinder must be installed by a G3 Competent Person (registered with a relevant scheme such as CIPHE, APHC or similar). The electrical connection must be made by a qualified electrician. The boiler warranty requires registration within 45 days of purchase.
Can it work with solar PV?
Yes. The cylinder includes an immersion heater boss, and the boiler is compatible with solar PV diverters such as Solar iBoost+ or myenergi eddi. Surplus solar generation can be diverted to heat the cylinder, reducing electricity running costs substantially on sunny days.
What is included in the package?
The unit includes: 9kWkW single-phase electric heat-only boiler (with built-in expansion vessel, circulator pump, pressure gauge, filling loop, touchscreen controls and safety cut-out), mounted onto a 150L pre-plumbed duplex stainless steel unvented indirect cylinder (with pre-fitted pipework, immersion heater, T&P relief valve and tundish connection). Flexi hoses, fixings and electrical cable are not included.
Related Products
Strom Electric Heat-Only Boiler (Boiler Only)
Boiler-only option for pairing with existing cylinder
Strom Prime2o Unvented Cylinder (Cylinder Only)
Standalone cylinder for pairing with existing boiler
Solar iBoost+ Solar Diverter
Divert surplus PV to heat the cylinder immersion
myenergi eddi PV Diverter
Intelligent solar diverter compatible with this installation
BTU & WATT Calculator
Room Dimensions
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)
Required Heating
0
Watts
0
BTUs
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