All-Electric Heating for Flats & Homes: Why the Strom Pre-Plumbed System Changes Everything

What Is the Strom A.I.One?

The Strom A.I.One (All-In-One) is a pre-plumbed electric heating package that combines two of Strom's most popular products into a single, factory-assembled frame: their compact heat-only electric boiler and the Prime2o unvented hot water cylinder, manufactured in their Ossett facility in West Yorkshire. Rather than an installer assembling and commissioning these components separately on site, the A.I.One arrives ready to connect — the boiler is already mounted on the cylinder frame, pipework is factory-routed, the circulation pump, expansion vessel, and safety valve group are pre-fitted, and the electrical connections are pre-wired from boiler to the pump circuit.

The result is a complete central heating and domestic hot water system in a single footprint, requiring only four connections on site: a cold mains inlet, a hot water outlet, a heating flow, a heating return — plus one electrical connection to the consumer unit. On a straightforward installation this can genuinely be commissioned in a fraction of the time of a conventional component-by-component build, which is particularly valuable in flat developments, new build programmes, or housing association upgrades where labour cost per unit matters.

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The Technology Inside

The A.I.One is built around two distinct technologies working in combination, and understanding both helps you size and specify the right unit for a given property.

The Strom Heat-Only Electric Boiler

At the heart of the system sits Strom's heat-only boiler, available in four single-phase output ratings: 6kW, 9kW, 11kW, and 14.4kW. Unlike a conventional gas boiler where combustion and heat exchange are complex processes with many failure points, the Strom boiler uses a patented flat serpentine heating element — a direct-contact heat exchanger where water flows across the entire surface area of a multi-strand element rather than through a tube inside a separate tank.

The boiler operates between 20°C and 80°C flow temperature at system pressures of 0.5–1.5 bar, uses 3/4" male heating connections (Strom recommend flexible hoses to protect the internal pipework from torque), and the 15mm PRV is pre-fitted in the A.I.One package. A digital control panel shows flow and return temperatures, pump status, frost protection status, and whether the unit is actively calling for heat — familiar territory for any installer used to working with modern boiler controls.

The Prime2o Unvented Cylinder

The cylinder half of the A.I.One is Strom's Prime2o indirect unvented cylinder, constructed from duplex stainless steel and guaranteed for 25 years against manufacturing defects. "Unvented" means it operates at mains water pressure — typically 2–3 bar for most UK properties — rather than relying on a gravity cold-water tank in the loft. This gives mains-pressure hot water at every tap and shower, with no roof tank, no risk of tank overflow, and no gravity-dependent flow rate.

The cylinder contains a single internal coil rated at 18.25–19.94kW (depending on cylinder size) through which the heating circuit water passes, transferring its heat to the stored domestic water without the two circuits ever mixing. The cylinder also has a factory-fitted immersion heater boss for a backup direct-heating element if required. Importantly, the A.I.One package pre-mounts the expansion vessel, temperature and pressure relief valve, and tundish discharge pipework — all items that Strom's installation manual requires and that commonly add time and cost when fitted individually.

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Why a Hot Water Cylinder Matters on an All-Electric System

This is the most important concept for homeowners switching from gas to understand. On a gas combi boiler, hot water is generated instantaneously — gas ignites, the heat exchanger warms the water in real time, and as long as gas is flowing the system can satisfy unlimited simultaneous demand. Electric systems fundamentally work differently.

The electrical supply into most UK homes is single-phase at 230V. Even a 14.4kW electric boiler — the largest single-phase unit in the Strom A.I.One range — draws around 62 amps continuously at rated output. That is simply the physical upper boundary of what single-phase domestic wiring and a standard domestic consumer unit can deliver without a costly supply upgrade. At 14.4kW you can fill a bath, but it will be slow. At 6kW or 9kW, a bath from an instantaneous electric combi is not realistic.

There is a further advantage specific to all-electric homes that makes a cylinder even more valuable: tariff flexibility. Smart electricity tariffs such as Octopus Intelligent, Agile, or Economy 7/10 offer significantly cheaper rates at off-peak times — often overnight between midnight and 7am, or during periods of grid surplus. A cylinder programmed to heat during these windows stores cheap energy for use throughout the day, fundamentally changing the economics of electric domestic hot water. A combi electric boiler has no such ability — it draws at full rate whenever hot water is demanded, regardless of tariff.

The Strom Prime2o cylinder's heat loss specification matters here too. The 150L unit loses just 1.32 kWh per 24 hours — meaning a fully charged cylinder at 65°C at midnight will still be at usable temperature the following evening, even with no re-heating in between. The 170L and 200L units lose 1.63 and 1.7 kWh per day respectively — still extremely low for their volume, and the trade-off against greater hot water capacity is almost always worthwhile in family-sized properties.

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Choosing Your Cylinder Size: 150L, 170L, or 200L

The A.I.One is available with three cylinder capacities. The choice is primarily driven by the number of people in the household and daily hot water demand. As a rule, a cylinder needs to be able to meet your total peak daily demand in a single charge — so it must be large enough to cover a morning routine without running cold. The sizing below uses standard UK hot water demand figures as a guide.

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Choosing Your Boiler Output: 6kW to 14.4kW

The boiler output determines two things independently: how quickly the cylinder recharges, and how much heat the boiler can provide to your radiators or underfloor heating circuits at any given time. These must both be considered — and importantly, they should be sized separately. Do not size according to how quickly you want hot water without first confirming the boiler output is adequate for your heating demand, and vice versa.

Strom's installation manual is explicit on this point: Part L 2022 of the UK Building Regulations prohibits significantly oversizing boilers, and because electric boilers are 100% efficient, an old gas boiler that was oversized for the property cannot simply be replaced like-for-like. A qualified installer must carry out a proper heat loss calculation for the property.

A useful way to understand the cylinder reheat time at each kW rating: a 150L cylinder needs approximately 8.5 kWh of energy to heat from cold (10°C) to 65°C. A 6kW boiler delivers that energy in around 1 hour 25 minutes of continuous running; a 14.4kW boiler does it in around 35 minutes. In practice with off-peak tariff scheduling, the reheat time matters less than ensuring the cylinder is charged before your peak demand period — but for properties with fast-cycling demand (such as HMOs or accommodation), a higher boiler rating accelerates recovery.

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Electrical Requirements and Supply Considerations

The Strom A.I.One operates entirely on single-phase 230V supply — the same domestic electricity supply used by all UK homes. There is no three-phase requirement, which is an important practical advantage over larger electric boilers and some heat pumps. However, the boiler does draw significant current, and the electrical installation has several requirements that must be met for both safety and warranty compliance.

Two points deserve particular attention. First, the 14.4kW model draws 62A at rated output. Many older UK consumer units have a main fuse or cutout rated at 60–80A total. If other high-draw appliances (electric shower, EV charger, induction hob) are on the same supply, a load assessment is essential — you may be close to or at the property's maximum supply capacity. Your electrician must measure the actual voltage at the supply to the property, not assume it is exactly 230V; variance above nominal increases the current draw proportionally and changes the cable and breaker sizing.

Second, Strom's design produces a higher-than-average level of intentional earth leakage current for the safety protection systems to function correctly. If a Type A or Type B RCD is fitted as part of the circuit protection, this may cause nuisance tripping. Your electrician should measure earth leakage at commissioning and may need to provide the boiler with its own dedicated RCD, or confirm that the circuit design does not require one for compliance.

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Installation: What "Pre-Plumbed" Actually Means

The term pre-plumbed is used a lot in the industry but means different things depending on the product. For the Strom A.I.One specifically, the factory assembly includes the following — all of which would otherwise be individual line items in a conventional boiler-and-cylinder installation:

• Boiler factory-mounted to the cylinder frame in the correct orientation
• Heating circuit pipework routed between boiler flow/return and cylinder coil connections
• Circulation pump pre-fitted and pre-wired to the boiler PCB
• Heating expansion vessel pre-installed and pre-charged
• Pressure relief valve pre-fitted and positioned
• Cylinder temperature and pressure relief valve (T&P) pre-fitted
• Tundish and discharge pipe routing pre-set (installer connects the final discharge pipework to drain)
• Boiler digital display and control board factory-configured

What the installer still needs to provide on site are the four plumbing connections (cold mains in, hot water out, heating flow, heating return), the electrical supply to the unit (including cable, isolator, and MCB sized to the boiler output), an external thermostat and programmer (the boiler has no internal timer — time and temperature control is always external), the automatic bypass valve on the heating circuit, zone valves if the system has more than one heating zone, and the tundish discharge pipework from the T&P valve to a safe disposal point.

One installation consideration unique to the pre-plumbed format is access and positioning. The unit must be placed on a structurally sound floor surface capable of bearing its full weight (up to 253kg for the 200L when full), positioned in an upright orientation at all times, and with a minimum 100mm clearance on all sides for airflow and future servicing access. It requires a floor drain or safe tundish discharge route nearby for the T&P valve. As with all unvented systems, installation must comply with G3 of the Building Regulations and be carried out by a qualified engineer holding a relevant unvented cylinder qualification (such as Part P and G3 competency, or equivalent).

Strom's installation manual also specifies that the system must be properly flushed before commissioning — if installed into an existing heating circuit, a power flush of existing radiators and pipework is required to remove debris that could block the pump or damage the heating element. System inhibitor must be added to the heating circuit water. These requirements are standard for any electric heating installation but are worth confirming with the installer before work begins, as they affect the total installation timeline.

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Applications: Where the A.I.One Excels

A Note on Underfloor Heating Specifically

Underfloor heating is an excellent pairing with the Strom A.I.One for several reasons beyond simple compatibility. UFH systems work most efficiently at lower flow temperatures — typically 35–45°C for well-insulated properties, up to 55°C for older screeds. Because the Strom boiler modulates down to as little as 1kW, it can maintain these lower temperatures accurately without the on/off cycling that causes energy waste in fixed-output systems. This matters particularly in flats and well-insulated new builds where the heating load is low and the boiler would otherwise short-cycle at minimum output.

The cylinder also helps here. UFH typically runs on a slow, continuous or semi-continuous heating regime rather than the sharp peaks of a radiator system. The combination of a programmable room thermostat controlling zone actuators on the UFH manifold, feeding a switch-live signal to the Strom boiler, is a proven and simple control strategy. For properties with both UFH and radiators on separate zones — common in mixed renovations or extensions — the A.I.One works equally well as the heat source for a two-zone system using a two-port valve on each zone and a junction box for the zone switching logic, consistent with Part L requirements for properties under 150m².

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Shop Our Strom A.I.One Range

We stock the full Strom A.I.One pre-plumbed package range at AIZO Quality Heating. Each unit is the genuine factory-assembled Strom product shipped from their UK facility, backed by Strom's 5-year boiler warranty (2 years parts and labour, 3 years parts, on registration within 45 days of purchase) and the Prime2o cylinder's 25-year manufacturing guarantee. All units are supplied with the installation manual; certification documentation is provided by the installing engineer.

The table below shows the available combinations and the corresponding product codes from Strom's specification sheet. Not all combinations are available — the 6kW boiler is only paired with the 150L cylinder, and the 200L cylinder requires a minimum 11kW boiler to ensure reasonable reheat times.