The Stiebel Eltron DEM 3 Set (product no. 236584) is a 3.5 kW mini instantaneous water heater designed to deliver hot water on demand to a single hand washbasin. Featuring full electronic closed-loop control with an outlet temperature sensor, it maintains the set outlet temperature to within one degree — without the need to blend cold water at the tap. The unit ships complete with a standard 13 A plug, making it the quickest-to-install option in the DEM Set range. Equally suited to oversink or undersink mounting, and compatible with both pressurised and non-pressurised taps, the DEM 3 Set is ideal for cloakrooms, staff washrooms, offices, and any location where cold-water-only supplies need a compact, point-of-use hot water solution.
3.5 kWRated Output
15.2 ARated Current
16 ACircuit Fuse
30–50 °CTemp. Range
IP25Protection Rating
1.70 kgWeight
Installer Notice — Electrical:
Although the DEM 3 Set includes a standard 13 A plug, the socket must be protected by a dedicated 16 A RCD-protected circuit compliant with BS 7671 and Part P of the Building Regulations. Do not share this circuit with other high-load appliances. Installation must be carried out by a qualified electrician.
Installer Notice — Water Resistivity:
This appliance uses a bare wire heating element. The electrical resistivity of the cold-water supply must be ≥ 1000 Ω·cm (conductivity ≤ 1000 µS/cm) at inlet temperatures up to 25 °C, or ≥ 1300 Ω·cm (conductivity ≤ 770 µS/cm) above 25 °C. Verify local water quality before installation. Do not install on demineralised or RO water supplies without specialist advice.
Anti-Scalding Temperature Lock:
The internal permanent temperature limit is factory-set and provides child-safe, fixed anti-scalding protection. If this limit requires adjustment, it must be set by a qualified contractor — it is not user-accessible. The user-adjustable range is 30–50 °C.
Plug-and-Play Convenience:
The DEM 3 Set is the only model in the DEM Set range supplied with a standard 13 A mains plug, reducing installation time significantly. The remaining DEM Set models (DEM 4 and DEM 6) require hardwired connections.
Key Features
Electronic Closed-Loop Temperature Control
A dedicated outlet temperature sensor feeds real-time data to the onboard control electronics. The system continuously adjusts heating output so the water reaches exactly the set temperature — no cold-blending required. This eliminates the energy waste and user frustration of manual tap adjustment.
Bare Wire Heating Element
The maintenance-free bare wire heating system transfers heat directly into the water stream with minimal thermal mass, delivering instant hot water from the moment the tap opens. The element is suitable for both hard and soft water areas, resisting scale build-up that can compromise conventional elements.
Anti-Scalding Protection
Automatic output matching ensures that if the incoming cold-water supply temperature rises unexpectedly, the unit reduces output power proportionally to prevent outlet temperatures exceeding safe limits. A fixed internal temperature limit provides a permanent, child-safe backstop that cannot be accidentally overridden.
PROFI-RAPID Installation System
The PROFI-RAPID back panel doubles as a drill template, slotted to compensate for drill-hole discrepancies. Wall mounting requires just two fixings. The cover and internal assembly detach with a single hand movement, and external metal water fittings allow direct tap installation without additional adaptors.
Oversink and Undersink Versatility
A single appliance covers both installation orientations. The unit can be rotated 180° for oversink or undersink positioning to suit the available space. External metal G 3/8 A water connections are positioned to align with either configuration, and the power cable is pre-wired to length.
Pressurised and Non-Pressurised Tap Compatibility
The DEM 3 Set operates with both open-outlet (non-pressurised) taps and standard pressurised taps. An integral flow controller and special aerator are included to optimise the flow pattern and maintain consistent performance across different tap types and mains pressures.
LED Diagnostic Traffic Light
A built-in three-LED diagnostic indicator provides at-a-glance fault analysis during commissioning and servicing, helping engineers identify electrical and flow faults quickly without requiring specialist tools.
Point-of-Use Efficiency
By heating water directly at the draw-off point and only when the tap is open, the DEM 3 Set eliminates the standing heat losses and dead-leg waste associated with cylinder-fed or central instantaneous systems. Energy is consumed only for the water actually used, making it highly efficient in low-demand, single-basin applications.
Technical Specification
| Identification |
|---|
| Product Number |
236584 |
| Model |
DEM 3 Set |
| Electrical |
|---|
| Rated Voltage |
230 V (1/N/PE) |
| Rated Output at 230 V |
3.53 kW |
| Rated Output at 200 V |
2.7 kW |
| Rated Output at 220 V |
3.2 kW |
| Rated Output at 240 V |
3.8 kW |
| Rated Current at 230 V |
15.2 A |
| Circuit Fuse (all voltages) |
16 A |
| Frequency |
50 / 60 Hz |
| Connection |
1/N/PE — standard 13 A plug supplied |
| Water |
|---|
| Water Connection |
G 3/8 A (external metal fittings) |
| Switch-On Flow Rate |
> 1.5 l/min |
| Water Resistivity ρ₁₅ ≥ (inlet ≤ 25 °C) |
1000 Ω·cm (conductivity ≤ 1000 µS/cm) |
| Water Resistivity ρ₁₅ ≥ (inlet > 25 °C) |
1300 Ω·cm (conductivity ≤ 770 µS/cm) |
| Performance |
|---|
| Outlet Temperature Range |
30–50 °C (user-adjustable) |
| Internal Anti-Scalding Limit |
Fixed — qualified contractor only |
| Control Method |
Electronic closed-loop (outlet sensor) |
| Physical |
|---|
| Height |
143 mm |
| Width |
190 mm |
| Depth |
82 mm |
| Weight |
1.70 kg |
| Colour |
White |
| IP Rating |
IP25 (splash-proof) |
Frequently Asked Questions
Does the DEM 3 Set come ready to plug in?
Yes. Unlike the DEM 4 and DEM 6 Set models, the DEM 3 Set is the only variant in the range supplied with a standard 13 A mains plug. However, the socket must still be on a dedicated 16 A RCD-protected circuit — it must not be shared with other high-current loads. Installation must comply with BS 7671 and should be carried out by a qualified electrician.
Can it be installed above or below the basin?
Yes. The DEM 3 Set is designed for both oversink and undersink installation using the same unit. Rotating the appliance 180° changes the orientation, and the external G 3/8 A water fittings and cable routing accommodate both configurations. The PROFI-RAPID back panel acts as a drill template, making accurate positioning straightforward.
Does the DEM 3 Set work with a non-pressurised (open outlet) tap?
Yes. The appliance is compatible with both pressurised taps and non-pressurised (open-outlet) taps. An integral flow controller and special aerator are included to ensure optimal water flow patterns for both types. Confirm tap compatibility before ordering.
Is it suitable for hard water areas?
Yes. The bare wire heating element used in the DEM 3 Set is inherently resistant to scale build-up and is approved for both hard and soft water areas. There is no anode rod or sacrificial component to inspect or replace. However, the water resistivity must meet the minimum specification (≥ 1000 Ω·cm at ≤ 25 °C inlet temperature) — verify your local supply before installation.
How does the electronic control prevent scalding?
The DEM 3 Set uses two complementary protections. First, the closed-loop outlet sensor continuously adjusts output to hold the set temperature. Second, the automatic output matching function reduces power if the incoming water temperature rises unexpectedly, preventing the outlet exceeding safe limits. A permanent internal temperature limit (set by a qualified contractor) provides a fixed backstop that cannot be accidentally altered by the user.
What maintenance does the DEM 3 Set require?
Routine maintenance is minimal. The bare wire element is maintenance-free. The built-in strainer should be inspected and cleaned periodically — particularly during initial commissioning and after any work on the incoming water supply. If the unit has been drained or isolated for more than a short period, it must be re-vented before restoring power to protect the heating element. No annual Gas Safe or G3 inspection is required.
