DEL 18 AU / DEL 27 AU

  • Made in Germany
  • Temperature selection up to a maximum of 50°C - overcoming the need for a tempering valve (G12 NZ Building Code)
  • Accurate hot water temperature through 3i Technology
  • Barewire element suitable for hard and soft water areas
  • Instantaneous, endless supply of hot water
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Product Overview

The STIEBEL ELTRON DEL AU three-phase 415V electric mains pressure instantaneous hot water systems provide instant hot water up to a maximum of 50°C with the reliability you have come to expect from STIEBEL ELTRON. These instant hot water heaters utilise sophisticated electronic technology to maintain a hot water delivery temperature not exceeding 50°C. This overcomes the need for a separate tempering valve in situations where 50°Celsius hot water is required.

Available at:
Or your local plumbing supply store.

Product Details

Engineering excellence from STIEBEL ELTRON

  • Made in Germany, designed for New Zealand conditions
  • Electronically controlled to accurately regulate the water temperature
  • Electronic safety system with air detection
  • LED display shows hot water temperature selection
  • Memory function and TMax function for premium comfort and safety
  • WaterMark Lic No. WMKA00301, AS3498

Efficient by design

  • Heats water to a maximum of 50°C
  • Point of use installation saves water by not waiting for hot water to arrive at the outlet
  • The three-phase water heater saves power due to the fact that no water is stored

Installation flexibility

  • Maximum hot water output temperature 50°C, no tempering valve needed (complies with the G12 New Zealand Building Code)
  • Bare wire element provides quick control over the water temperature and is suitable for hard or soft water areas
  • Compact in size for space saving installation
  • No safe tray required
  • No ventilation required

Available in electrical size:

  • DEL 18 AU - 19.4kW, 27 Amps per phase, three phase 415V
  • DEL 27 AU - 28kW, 40 Amps per phase, three phase 415V


  • 5 year full parts and labour domestic warranty*

*Conditions apply - refer warranty policy for full details.

Technical Data

Model number DEL 18 AU DEL 27 AU
Rated output (415V) 19.4kW 28kW
Rated current (415V) 27Amp 38.9Amp
Phases 3/PE 3/PE
Electrical Installation As per AS/NZS3000
Installation requirements AS/NZS3500.4.2 & local requirements
Switch on flow rate (minimum flow rate required to switch on the water heater) 2.5L/min 2.5L/min
Permissible operating pressure 1000kPa 1000kPa
Temperature adjustment 30-50°C 30-50°C
IP Rating IP25 (IP24 at electrical connection finished walls) IP25 (IP24 at electrical connection finished walls)
Height 478mm 478mm
Width 225mm 225mm
Depth 105mm 105mm
Weight (filled with water) 4kg 4kg
Colour white white
Nominal capacity 0.4L 0.4L
Flow rate limiter (if fitted) L/min 7.5 (blue) | 12 (brown) 7.5 (blue) | 12 (brown)
Approvals WaterMark Lic No. WMKA00301, AS3498
For one/several draw off points Yes/Yes Yes/Yes
Heating system Bare wire Bare wire
Electronic flow rate control - -
Electronic air detection system Yes Yes
Accepts pre-heated water (solar) Yes (incoming water must not exceed 50°C)
Programmable temperature Yes Yes
Wellness shower programs - -
ECO energy & water function - -


File Category Type Download
DEL AU Data SheetData SheetPDF
663.25 kB
DEL AU Operation and InstallationOperation and Installation GuidePDF
10.83 MB
DEL AU WarrantyWarrantyPDF
109.73 kB
718.99 kB
Revit file of STIEBEL ELTRON's DELTechnical DrawingRFA
396.00 kB
STIEBEL ELTRON Tech Line Drawing DELTechnical DrawingJPG
1.84 MB
STIEBEL ELTRON Exploded Diagram DEL AUExploded DiagramPDF
205.88 kB
Model & Serial Number LocationSerial Number LocationPDF
141.08 kB


1. How do I know if I have 3 phase power available at my property?

Contact your local energy provider and inform them of your address. They will be able to let you know if you have three-phase power available at your address.

2. I have 3 phase power at my property, can I install a DEL AU instant hot water system?

You will need to check with your electrician to find out how much three-phase power is available in "Amps per phase". The DEL 18 AU water heater requires 27 Amps per phase, whereas the DEL 27 AU requires 40 Amps per phase.

3. I have a 3 phase electric instantaneous unit I want to replace, what STIEBEL ELTRON system should I select?

You will need to confirm the amperage supply to the hot water unit from the circuit breaker in the switchboard. Please contact us to confirm the appropriate instantaneous electric hot water system.

4. What size instantaneous electric water heater do I need for my apartment or house?

As a general rule, the instant hot water system required will be based on the number of hot water outlets the hot water system needs to service, along with the incoming cold water temperature. As a general guide in an apartment/house with 1 bathroom, a 19.4kW three-phase electric instantaneous water heater (e.g. DHE 18 AU, DEL 18 AU or DHB-E 18 AU) is suitable. In a house with 2 bathrooms, a 28-29.1kW three-phase electric instantaneous water heater (e.g. DHE 27 AU, DEL 27 AU or DHB-E 27AU) should be selected.

5. How can I tell if I have a DEL 18 AU or a DEL 27 AU?

Underneath the dial that adjusts the temperature there is a flap that pulls forward and then drops down. A rating label is located up under the flap showing the model and size - DEL 18 AU or DEL 27 AU.  Within the downloads section of the DEL you can download a pdf showing you exactly where and how to locate this sticker.

6. What hot water temperature can the DEL AU water heaters deliver?

The STIEBEL ELTRON DEL AU instantaneous electric water heater delivers hot water not exceeding 50 degrees Celsius in accordance with AS3498, overcoming the need for a temperature control device in hygienic areas where hot water must be limited to 50°C.

7. Does the DEL AU need a tempering valve to limit the hot water to 50 degrees Celsius?

No, the DEL AU hot water system delivers hot water not exceeding 50 degrees Celsius in accordance with AS3498, overcoming the need for a tempering valve in hygienic areas where the water must be limited to not exceed 50°C.

8. Where can the DEL AU instant hot water system be installed?

The DEL AU water heater can be installed almost anywhere due to its compact size. The water heater does not require ventilation, relief drain or safe trays so it can be installed in a cupboard, in the roof space, below the sink, in a service cavity, in a Euro laundry just to name a few options. If installing outdoors, the hot water system must be protected from the elements by a protective covering such as a meter box.

9. How far can the water heater be installed from the hot water outlet?

The DEL AU water heaters are designed to be installed as close as practical to the most used hot water outlet. Installing closer to the point of use can help to save water and energy by delivering hot water quickly to the outlet. The STIEBEL ELTRON 3 phase electric instantaneous water heaters are designed to service multiple outlets located several metres away from the system.

10. How efficient is an instantaneous electric water heater compared to an electric storage hot water system?

Compared to a storage hot water unit an electric instantaneous water heater can be at up to 30% more efficient. This is due to the water heater not storing any hot water and not having heat losses from storing a body of hot water.

11. Where can I purchase a DEL AU water heater?

The DEL AU water heater range is available from all leading plumbing stores.

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