The EHS Primus 14000C Flex is a 14kW single-phase electric combi boiler with fully range-rated heating and hot water outputs — the installer sets both power levels at commissioning to match the exact heat loss and hot water demand of the property, rather than selecting a fixed-output model. It delivers continuous hot water up to 7 litres per minute and central heating through existing radiators or underfloor heating, with no flue, no gas connection, and no annual Gas Safe inspection required. Part of the EHS FLEX range, it is designed as a direct replacement for a gas combi boiler in properties where a flue route is impractical or unavailable.
14 kW
Max heating & DHW output
6.5 L/min
DHW flow (30°C rise)
No flue
Site anywhere indoors
5 yrs
Manufacturer warranty
⚠ Qualified Installation & Electrical Supply Required
This boiler must be installed by a qualified heating engineer and a Part P registered electrician, in accordance with the EHS installation manual, BS 7671 IEE Wiring Regulations, Building Regulations, and the Water Supply (Water Fittings) Regulations 1999. At full 14kW output it draws 61A and requires a 63A circuit breaker and 10mm² cable as a minimum. An automatic bypass valve must be fitted — its omission can cause F6 error codes, boiler shutdown, and will affect the manufacturer's warranty.
⚠ Suitable for Single-Shower Properties, Not Baths
EHS specify the 14kW combi as suitable for properties with a single shower — the maximum flow rate of approximately 6.5–7 L/min is not sufficient to fill a bath in reasonable time. For properties with baths or multiple bathrooms, EHS recommend a system boiler paired with a hot water cylinder instead.
✔ Range-Rated Flex — One Boiler, Any Property
Both heating and hot water outputs are adjustable at installation, from 2kW up to the 14kW maximum, in six power steps. The installer matches output to the heat loss calculation rather than selecting a fixed model — EHS recommend not reducing DHW output below 12kW where a shower is present.
✔ No Flue — No Gas — No Annual Certificate
With no combustion, no flue, and zero risk of carbon monoxide emission, the boiler can be sited in any interior room — kitchen, hallway, or cupboard — without a flue route to an external wall, and requires no annual Gas Safe safety certificate.
✔ Continuous Hot Water at 6.5–7 L/min
At full 14kW output the boiler raises incoming mains temperature by 30°C at 6.5 litres per minute — sufficient for a standard shower. EHS specify restricting incoming flow to 5–6 L/min to guarantee this temperature rise regardless of mains pressure.
✔ Touch-Screen Display with 24-Hour Timer
A colour touch-screen interface provides direct control of heating mode, hot water temperature, timer programming, frost protection and pump purge — all without needing an external controller for basic operation.
✔ Built-In Frost Protection — Two-Stage
A two-level frost protection system monitors internal temperature whenever the boiler is powered, activating the pump and then the heat exchanger as temperatures fall, to protect the system from freeze damage during cold spells.
✔ Solar PV & Off-Peak Tariff Compatible
The range-rated output and built-in timer allow heating to be scheduled around cheap-rate tariffs or run at reduced output to absorb surplus solar PV generation, supporting lower running costs.
Performance
Heating Power
14kW (range-rateable in 6 steps from 2.3kW)
Hot Water Power
14kW (range-rateable — not recommended below 12kW with a shower fitted)
Function
Heating and Hot Water (Combi)
Hot Water Flow Rate (30°C rise)
6.5 L/min at full power; restrict incoming flow to 5–6 L/min
Heating Flow Temperature Range
30°C – 80°C (radiator mode); 30°C – 60°C (underfloor heating mode)
Hot Water Temperature Range
30°C – 60°C
Electrical
Voltage
230V AC single phase
Current at Rated Output (14kW)
61A
Minimum Circuit Breaker (MCB/RCB)
63A
Thermostat Connection
Zero-volt — must never be supplied with live power
Plumbing & Physical
Water Pressure Range
1–3 bar (max 6 bar mains — fit pressure reducing valve if higher)
Flow & Return Connection
G¾" male thread
Inlet & Outlet Connection
G½"
Internal Expansion Vessel
5 litres
IP Rating
IPX1 (indoor use only — not for bathrooms or shower enclosures)
Dimensions
585mm × 380mm × 235mm
Compliance & Warranty
Wiring Standard
BS 7671 IEE Wiring Regulations
Installation Standards
BS EN 12828, BS EN 12831, BS EN 14336, BS 7593
Manufacturer Warranty
5 years (register within 30 days at ehs-heating.com)
Extended Warranty
+2 years (7 total) when purchased with the EHS Installer Kit and registered
Is 14kW enough to heat my property?
This depends on the heat loss of the property — size, insulation standard, and number of radiators. EHS recommend completing a heat loss calculation to BS EN 12831 before ordering. As a guide, a well-insulated one or two-bedroom flat up to approximately 70m² is typically suitable for a 14kW electric combi. Because the boiler is range-rated, the installer can set a lower maximum output if the heat loss calculation indicates this is more appropriate.
Why does the hot water need a flow restrictor?
The heat exchanger can only add a fixed amount of heat per litre of water passing through it. At 14kW and 6.5 L/min the rise is around 30°C — comfortable for a shower. If mains pressure pushes flow above this without restriction, the same 14kW heats each litre by less, and the water may not reach a comfortable temperature. A 5–6 L/min flow restrictor caps the flow at a rate the boiler can always satisfy.
Why is the automatic bypass valve mandatory?
As thermostatic radiator valves (TRVs) close when rooms reach temperature, the heating circuit becomes increasingly restricted. Without a bypass, the pump forces water against a closing circuit, pressure rises, and flow drops. The boiler's paddle flow switch detects this and triggers an F6 error code or shuts down to protect the heat exchanger. The automatic bypass valve prevents this by opening progressively as pressure rises.
Can this boiler be used with underfloor heating?
Yes. Underfloor heating mode is selected via the engineer's control panel and limits the flow temperature to 30°C – 60°C, appropriate for UFH systems, as opposed to the 30°C – 80°C range available in radiator mode.
Does this boiler require an annual service?
Yes — a yearly service by a suitably qualified engineer is a condition of the EHS warranty. The magnetic filter should be checked at every service, and a record of the service must be kept by the owner to remain covered under the warranty terms.
What is included versus what needs to be bought separately?
This listing is for the boiler unit only. Mandatory components for a compliant installation — automatic bypass valve, magnetic filter, WRAS filling loop, isolation valves, DHW flow restrictor, and a Boiler Plus compliant thermostat — are supplied together in the EHS Installer Kit (EHS-COMBIKIT251F), which also extends the manufacturer warranty to 7 years when registered.
