The Heatrae Sadia Amptec is a compact electric flow boiler that provides wet central heating and domestic hot water with the comfort and controllability of a gas central heating system — wherever there is a mains electricity supply but no gas. Available in 4kW, 6kW, 9kW, 11kW, and 12kW outputs, in both a C-Series for conventional radiator systems (65–80°C flow temperature) and a U-Series for underfloor heating (30–60°C), the Amptec is the established choice for off-gas-grid properties, loft conversions, extensions, apartments, and situations where fluing restrictions prevent the use of a gas boiler. The slender 1050 × 90 × 90mm body — the same footprint across all outputs — installs onto any internal wall in a vertical orientation via two keyhole slots, connects to existing 22mm pipework, and works with standard radiators, programmers, circulating pumps, room thermostats, and TRVs without modification. 99.8% efficient at point of use. Solid state technology with no moving parts, soft start electronics, zero volt switching, and front panel fault indication. 2-year on-site parts and labour guarantee.
⚠ Qualified Electrical & Plumbing Installation Required — The Amptec must be permanently connected to a double-pole linked switch with minimum breaking capacity suitable for the load, wired in accordance with current IET Wiring Regulations (BS 7671). Each model requires a dedicated circuit — MCB ratings range from 20A (4kW) to 63A (11kW and 12kW). Installation should be carried out by a Part P registered electrician working with a qualified heating engineer. Must be mounted vertically only.
ℹ C-Series or U-Series — Which Do You Need?
C-Series (C400 / C600 / C900 / C1100 / C1200): Flow temperature 65–80°C. The standard choice for conventional radiator systems, S-plan and Y-plan heating layouts with an indirect cylinder, and properties where standard panel radiators are the heat emitter. Compatible with thermostatic radiator valves and standard room thermostats.
U-Series (U401 / U601 / U901 / U1101 / U1201): Flow temperature 30–60°C. Specifically designed for wet underfloor heating systems, where the lower flow temperature prevents damage to floor finishes and is thermally optimised for UFH manifold delivery. Also suitable for heat pump compatible low-temperature radiators. The hardware is identical — the difference is the thermostat range.
No flue
Any internal wall
2 years
On-site guarantee
Features & Benefits
✔ No Flue — Flexible Installation Location
With no combustion gases, the Amptec requires no flue terminal, no flue pipe, and no external wall penetration for the boiler itself. It can be installed on any interior wall — including in a hallway, under a staircase, in a kitchen cupboard, or in a loft conversion — without reference to external wall position or proximity to windows and doors. This is the single most significant practical advantage over gas boilers for difficult or space-constrained installations, and it means there are no planning constraints on boiler position in listed buildings or conservation areas where external flue terminals may be restricted or refused.
✔ Low Watts Density Copper Elements — Long Life
The Amptec uses long-life, low watts density copper heating elements in a copper heat exchanger — rather than the stainless steel or nichrome elements used in budget electric boilers. Low watts density means the heat flux at the element surface is deliberately kept low, reducing the temperature differential between the element and the water. This substantially reduces the rate of limescale deposition on the element surface in hard water areas, and lowers the thermal stress cycles on the element material — the two primary failure modes for electric heating elements. The result is measurably longer element life and more consistent performance over the product's service life.
✔ Solid State — No Moving Parts — Soft Start
The Amptec's control electronics are entirely solid state with no mechanical relays or contactors to wear or fail. Element switching uses zero volt switching — the elements switch on only when the AC mains voltage is at zero, eliminating the electrical arcing and interference that causes premature failure in relay-switched electric heating and reduces electromagnetic emissions. A soft start system ramps up element power gradually rather than applying full load instantaneously, preventing the voltage dip and current surge that can cause flicker on shared supply circuits and reduces stress on the element windings at switch-on.
✔ Drop-In Replacement — 22mm Connections
All Amptec models connect via 22mm copper compression connections (flow red, return blue) — the most common primary pipework size in UK heating systems. This means the Amptec is a straightforward drop-in replacement for an existing boiler on a 22mm primary circuit, with no pipework adaptation needed at the boiler connections. The 1050 × 90 × 90mm body is the same physical size across all five output ratings — specifying a higher kW model for a larger property does not require additional wall space or a larger enclosure. Wall mounting via two keyhole slots from a template; a pump supply (2A fused) is included in the boiler output terminals.
✔ No Annual Safety Certificate — Minimal Maintenance
Unlike gas or oil boilers, the Amptec carries no legal requirement for an annual safety inspection — there are no combustion products, no heat exchanger to inspect for flue gas leakage, and no CO risk. Landlords and property managers save the cost and administrative burden of annual boiler service certificates. Routine maintenance is minimal: the unit has no moving parts beyond any external pump, no ignition components, no gas valve, and no flue system to service. This makes the Amptec particularly attractive for rental properties and managed multi-unit buildings where compliance overhead is a significant operating cost.
✔ Multiple Units — Relay Accessories for Load Sharing
Two or more Amptec boilers can be installed in parallel to meet heating loads exceeding a single unit's capacity — for example, two 12kW units providing 24kW total for a larger property. Heatrae Sadia relay accessories coordinate operation: the RL2 and RL3 relays manage multiple Amptec units to share the total load and prevent simultaneous full-power start-up. The RL1 relay is used where an electric shower is installed in the same property — it prevents the shower and boiler operating simultaneously, protecting the incoming supply fuse from overload. These accessories allow the Amptec system to be scaled to properties of almost any size within single-phase supply limits.
Full Model Range — C-Series (Radiator) & U-Series (Underfloor)
| Model |
Output |
Temp Range |
Supply (A) |
MCB |
Weight |
Code |
| C400 |
4 kW |
65–80°C |
17A |
20A |
7.5 kg |
95:022:001 |
| C600 |
6 kW |
65–80°C |
25A |
32A |
7.5 kg |
95:022:002 |
| C900 |
9 kW |
65–80°C |
38A |
50A |
8.5 kg |
95:022:003 |
| C1100 |
11 kW |
65–80°C |
45A |
63A |
8.5 kg |
95:022:004 |
| C1200 |
12 kW |
65–80°C |
50A |
63A |
8.5 kg |
95:022:005 |
| U401 |
4 kW |
30–60°C |
17A |
20A |
7.5 kg |
95:022:101 |
| U601 |
6 kW |
30–60°C |
25A |
32A |
7.5 kg |
95:022:102 |
| U901 |
9 kW |
30–60°C |
38A |
50A |
8.5 kg |
95:022:103 |
| U1101 |
11 kW |
30–60°C |
45A |
63A |
8.5 kg |
95:022:104 |
| U1201 |
12 kW |
30–60°C |
50A |
63A |
8.5 kg |
95:022:105 |
Technical Specifications — All Models (Common)
| Manufacturer / Range |
Heatrae Sadia — Amptec
|
| Dimensions (H × W × D) |
1050 × 90 × 90 mm — identical across all output sizes |
| Nominal Water Capacity |
1.3 litres |
| Plumbing Connections |
22mm compression — flow (red) & return (blue) |
| Min. Flow Rate |
4kW & 6kW: 6 L/min · 9kW, 11kW & 12kW: 12 L/min |
| Max. Operating Pressure |
3 bar (pressure tested to 15 bar) |
| Heating Systems |
Sealed or open vented · S-plan · Y-plan · UFH (U-series) |
| Element |
Long life, low watts density copper in copper heat exchanger |
| Efficiency |
99.8% (ErP D-rated — see FAQ) |
| Thermal Insulation |
Armaflex closed-cell (dust, fibre & CFC free) |
| Outer Casing |
White stove-enamelled corrosion-resistant steel |
| Inner Container |
Copper |
| Power Supply |
240V ~ single phase (see model range table for amps) |
| Safety Features |
2A fused pump supply · Dual control circuits · Dual switching · Self-check & fault indication · Re-settable trips · Soft start · Zero volt switching |
| Approvals |
BEAB · CE · CCA · BS EN ISO 9001:2000 |
| Guarantee |
2 years on-site parts & labour (from date of purchase) |
Frequently Asked Questions
What size Amptec do I need for my property?
Sizing should always be based on a heat loss calculation to BS EN 12831, which your heating engineer can carry out. As a rough guide from Heatrae Sadia: the 4kW suits a small flat, mobile home or single extension; 6kW covers a small 1–2 bedroom flat with around 4 radiators; 9kW suits a 2–3 bedroom property with around 7 radiators; 11kW covers a larger 3–4 bedroom house; and the 12kW (or multiple units with RL2/RL3 relay accessories) covers larger properties or high-insulation buildings where the heat loss demands more capacity. If the boiler will also be heating a domestic hot water cylinder, add approximately 3kW to the calculated space heating requirement to account for cylinder reheat loads.
The Amptec is described as 99.8% efficient but has an ErP D-rating. How can both be true?
These two statements measure different things. The 99.8% efficiency figure measures the conversion of electrical energy into useful heat at the point of use — essentially all the electricity consumed by the Amptec becomes heat in the heating circuit, with only 0.2% lost as standing heat loss from the unit body. This is genuinely very high. The ErP D-rating is a different metric: it assesses the full life-cycle carbon and energy impact, which includes the efficiency of electricity generation at the power station. Because the current UK electricity grid is still partly generated from fossil fuels, the grid efficiency factor reduces the overall ErP score for all-electric heating products. As the grid decarbonises — increasing its share of wind, solar, nuclear and hydro — the effective carbon impact of electric heating improves. Properties already on 100% renewable electricity tariffs can reasonably treat the Amptec as a near-zero carbon heating option today.
Can this boiler work with my existing radiators and controls?
Yes — the Amptec is specifically designed as a drop-in replacement for a gas or oil boiler on an existing wet central heating system. It works with standard panel radiators, conventional thermostatic radiator valves (TRVs), wiring centres, zone valves (S-plan or Y-plan), programmers, and room thermostats without modification. The 22mm compression connections match standard UK primary pipework. The only change from a gas installation is the electrical supply — the existing gas supply is capped off and a new electrical circuit is run to the boiler position. The Amptec also includes a 2A fused pump supply terminal, allowing the circulating pump to be wired and powered via the boiler rather than separately.
Can I use the Amptec with solar PV to reduce running costs?
Yes — the Amptec is fully compatible with solar PV diversion systems. A solar diverter (such as a myenergi Eddi or iBoost) monitors surplus generation and diverts excess solar electricity to the Amptec rather than exporting it to the grid at a low SEG rate. For maximum benefit, the system should be sized so that the boiler's heating loads can be partially covered by daytime solar generation — most effective for DHW cylinder heating (which can be timed to the solar generation window) and background space heating during sunny daytime periods. Pairing the Amptec with battery storage and time-of-use tariffs (Octopus Go, Agile) can further reduce the effective running cost by shifting electricity consumption to low-rate overnight periods.
Does the Amptec need an annual service, and can landlords use it in rental properties?
There is no legal requirement for an annual safety inspection on the Amptec — unlike gas boilers, which require annual Gas Safe certificates under the Gas Safety (Installation and Use) Regulations 1998. For landlords, this removes the statutory annual cost and the obligation to arrange access for gas safety checks. However, Heatrae Sadia recommend periodic checks by a competent person — typically every 3–5 years — covering system pressure, water quality, element condition, and control function. The unit's re-settable trips and front panel fault indication assist with diagnosis if a problem occurs. For rented properties, the boiler must still be properly commissioned and the installation certificate retained as evidence of compliant installation under Part P.
What consumer unit supply do I need, and will my existing supply cope?
The Amptec requires a dedicated circuit from the consumer unit. Required MCB ratings are: 4kW → 20A; 6kW → 32A; 9kW → 50A; 11kW and 12kW → 63A. A 63A circuit for the 11 or 12kW models is a significant load — if your property has a 60A or 80A main incoming fuse (common in older properties), adding a 63A boiler circuit may exceed the total available supply. A Part P electrician should assess the consumer unit rating and total connected load before installation. In some cases a 100A supply upgrade from the DNO may be needed — this is typically free for residential properties and takes several weeks to arrange but should be factored into project timescales.
