Junkers miniMAXX WR 11-2 B Series Gas Heater Manual

Information about the heater

Category, type and approval no.

Model WRD 11/14/18 -2 B...
Category II2H3+
Type B11BS

Tab. 1

Technical identification code

W R D 11 -2 B 23
W R D 14 -2 B 23
W R D 18 -2 B 23

Tab. 2

W Water gas heater
R Proportional power adjustment
D Digital display
11 Capacity (l/min)
-2 Version 2
B Electronic ignition powered by 1.5 V batteries
23 Indicator number of natural gas H
31 Indicator number of LPG
S... Country code

Supplied materials

  • Gas heater
  • Attachment elements
  • Connection elements
  • Heater documentation
  • Two 1.5 V batteries type R
  • Rubber holders (LPG heaters).

Description of the heater

Operating convenience, as the heater is ready to operate by simply pressing a switch.

  • Heater for wall-mounting
  • Ignition by electronic device triggered when the water valve opens
  • Gauge to display temperature, burner operation and malfunctions
  • Temperature sensor to monitor the water temperature at the heater output
  • Great savings in comparison with conventional heaters, due to the possibility of power adjustment and no permanent pilot flame
  • Natural gas/LPG burner
  • Semi-permanent pilot burner which only functions during the period between the opening of the water valve and the ignition of the main burner
  • Heat exchanger without tin/lead covering
  • Water automatic in fibreglass-reinforced polyamide, 100% recyclable
  • Automatic adjustment of the water flow by means of a device which permits a constant flow to be maintained in spite of variable pressure supplies
  • Gas flow adjustment proportional to the water flow to maintain a constant high temperature.
  • Safety devices:
    • Ionisation probe to check for accidental extinction of the burner flame
    • Combustion gases monitoring device which turns off the heater in case of inadequate combusted gas evacuation conditions
    • Temperature limiter which prevents overheating of the heat exchanger

Special accessories

  • Conversion kit from natural gas to butane/propane and vice-versa.


Fig. 1

  1. Heat exchanger
  2. Burner
  1. Temperature/volume selector
  1. Gas connection
  1. Ignition unit
  2. Battery compartment
  1. Power selector
  1. LED - Burner status check
  2. Switch / LED - Battery status check
  3. Front
  4. Opening for mounting on the wall
  5. Connection collar to the combustion gases pipe
  6. Flue with non-return device
  7. Gas automatic
  1. Digital display
Dimensions (mm) A B C D E F G H (Ø)
Natural gas LPG
WRD11B 310 580 228 110 463 60 25 3/4" 1/2"
WRD14B 350 655 228 130 510 95 30 3/4" 1/2"
WRD18B 425 655 334 130 540 65 30 3/4" 1/2"

Tab. 3 Dimensions

Functional diagram of the heater

Functional diagram of the heater
Fig. 2 Functional Diagram

  1. Pilot burner
  2. Spark plug
  3. Ionisation probe
  4. Heat exchanger
  5. Main burner
  6. Injector

7a Screw for measurement of pressure in burner
7b Screw for measurement of input pressure

  1. Slow ignition valve
  2. Venturi
  3. Temperature/volume selector
  4. Water automatic
  5. Command cone
  6. Water flow regulator
  7. Water filter
  8. Micro-switch
  9. Cold water pipe
  10. Diaphragm
  11. Main gas valve
  12. Maximum gas adjusting screw
  13. Gas supply pipe
  14. Gas filter
  15. Hot water pipe
  16. Ignition unit
  17. Battery compartment
  18. Servo valve
  19. Power selector
  20. Gas valve
  21. Pilot valve
  22. Pilot injector
  23. Pilot gas pipe
  24. Temperature limiter
  25. Combustion gases monitoring device
  1. Temperature sensor

Electrical diagram

Electrical diagram
Fig. 3 Electrical diagram

  1. Spark plug
  2. Ionisation probe
  1. Micro-switch
  1. Ignition unit
  2. Battery compartment
  3. Servo valve (normally open)
  1. Pilot valve (normally closed)
  1. Temperature limiter
  2. Monitoring of combustion gases
  3. Diaphragm valve
  4. LED - Burner status check
  5. Switch / LED - Battery status check
  1. Temperature sensor
  2. Digital display


This gas heater is equipped with automatic electronic ignition which simplifies its operation.

  • To do so, just turn on the switch (Fig. 9).

After this procedure, automatic ignition occurs whenever a hot water tap is opened. First, the pilot burner is lit and approximately four seconds afterwards the main burner. The pilot burner flame is then extinguished after a short period of time.
This is a way of saving a great amount of energy as the pilot burner only operates for the minimum necessary time to ignite the main burner, in contrast to conventional systems which operate permanently.

information Air in the gas supply pipe when the heater is started up may cause ignition to fail.

If this happens:

  • Close and open the hot water tap to repeat the ignition process until all the air has been purged.

Technical characteristics

Technical characteristics Symbol Units WRD11 WRD14 WRD18
Power and flow
Nominal useful power Pn kW 19,2 23,6 30,5
Minimum useful power Pmin kW 7 7 9
Useful power (adjustment range) kW 7 - 19,2 7 - 23,6 7 - 30,5
Nominal thermal flow Qn kW 21,8 27 34,5
Minimum thermal flow Qmin kW 8,1 8,1 10,3
Gas data*
Supply pressure
Natural gas H G20 mbar 20 20 20
LPG (butane/propane) G30/G31 mbar 30/37 30/37 30/37
Natural gas H G20 m3/h 2,3 2,9 3,7
LPG (butane/propane) G30/G31 kg/h 1,7 2,2 2,75
Number of injectors 12 14 18
Water data
Maximum permissible pressure** pw bar 12 12 12
Temperature selector in fully clockwise position
Temperature rise °C 50 50 50
Flow range l/min 2 - 5,5 2 - 7 2 - 8,8
Minimum operating pressure pwmin bar 0,1 0,1 0,2
Minimum pressure for maximum flow bar 0,25 0,35 0,5
Temperature selector in fully anti-clockwise position
Temperature rise °C 25 25 25
Flow range l/min 4 - 11 4 - 14 4 - 17,6
Minimum operating pressure bar 0,2 0,2 0,2
Minimum pressure for maximum flow bar 0,6 1 1,3
Combustion products***
Minimum low pressure mbar 0,015 0,015 0,015
Flow g/s 13 17 22
Temperature °C 160 170 180

Tab. 4

* Hi 15°C - 1013 mbar - dry: Natural gas 34.2 MJ/m3 (9.5 kWh/m3)
LPG: Butane 45.72 MJ/kg (12.7 kWh/kg) - Propane 46.44 MJ/kg (12.9 kWh/kg)
** Considering the water dilution effect this value must not be exceeded.
*** For nominal calorific power


Any local by-laws and regulations pertaining to installation and use of gas-heated appliances must be observed. Please refer to the laws that should be attended in your country.


information The gas installation, the connection of exhaust/supply pipes as well as the initial startup are to be performed exclusively by authorised gas fitters.

information The heater can only be used in the countries indicated on the rating plate.

Important information

  • Before installing, call the gas company and check the standard relating to gas heaters and ventilation requirements for rooms.
  • Install a gas cut-off valve as close as possible to the heater.
  • After finishing the gas system, the pipes must be thoroughly cleaned and leak-tested; to avoid damaging the gas automatic by excess pressure, this test must be performed with the gas valve of the heater closed.
  • Check if the heater corresponds to the type of gas provided.
  • Check if the flow and pressure through the installed reducer are appropriate for the consumption of the heater (see technical data in the table 4).

Selection of the place of installation

Requirements regarding the place of installation

  • Do not install the heater in rooms with a volume of less than 8 m3 (not including the volume of the furniture providing this does not exceed 2 m3.
  • Comply with the specific instructions for each country.
  • Assemble the gas heater in a well-ventilated location where it will not be exposed to temperatures below zero and in a place where there is an evacuation pipe for combustion gases.
  • The gas heater must not be installed over a heat source.
  • To avoid corrosion, the combustion air must be free from harmful substances. Examples of particularly corrosive substances: halogenated hydrocarbons contained in solvents, paints, glues, engine gases and various domestic detergents. If necessary, take adequate measures.
  • Respect the minimum installation clearances indicated in Fig. 4.
  • The heater must not be installed in locations where the room temperature can reach 0°C.

In case of a frost risk:

  • Turn the heater off
  • Remove batteries
  • Purge the heater.
    Requirements regarding the place of installation
    Fig. 4 Minimum clearances

Combustion gases

  • All gas heaters must be connected in a leak-roof manner to a gas evacuation pipe of adequate dimensions.
  • The flue must:
    • be vertical (reduced horizontal sections or no horizontal sections at all)
    • be thermally insulated
    • have an exit above the maximum roof level
  • A flexible or rigid pipe should be used, fit it inside the flue socket. The external diameter of the pipe should be slightly smaller than the dimension specified in the appliances dimensions table.
  • The extremity of the evacuation pipe must be protected against wind/rain.

Ensure that the extremity of the evacuation pipe is placed between the ledge and the ring of the flue

If these conditions cannot be met, a different location must be selected for the gas intake and evacuation.

Surface temperature

The maximum surface temperature of the heater is less than 85°C, with the exception of the combustion gases evacuation device. No special protection measures are required for flammable construction materials or built-in furniture items.

Air intake

The place where the heater is to be installed must have an area of air supply according to the table.

Heater Minimum useful area
WRD11B ≥60 cm2
WRD14B ≥90 cm2
WRD18B ≥120 cm2

Tab. 5 Useful areas for air intake

The minimum requirements are listed above; however, each country's specified requirements must also be respected.

Heater mounting

  • Remove the temperature/flow selector and the power selector.
  • Unscrew the front fixing screws.
  • With a simultaneous movement towards you and upwards, release the front of the two lugs from the back.
  • Fix the heater vertically, using the provided screw hooks and plugs.

Never support the gas heater on the water or gas connections.

Water connection

It is advisable to purge the installation beforehand, because the presence of dirt may reduce the flow and, in extreme cases, cause a blockage.

  • Identify the cold water pipe (Fig. 5, item A) and the hot water pipe (Fig. 5, item B), so as to avoid any possible mis-connection.
  • Connect the water pipes to the water automatic using the provided connection accessories.
    Water connection
    Fig. 5 Water connection

information It is advisable to install a non-return valve on the supply side of the heater to avoid problems caused by sudden changes in supply pressure.

Gas connection

Any local by-laws and regulations pertaining to installation and use of gas-heated appliances must be observed.
Please refer to the laws that should be attended in your country.


  • Open the water and gas flow valves and check that all connections are leak-tight.
  • Insert the two batteries correctly (Fig. 8) 1.5 V type R supplied with the heater.
  • Check the combustion gases monitoring device is functioning correctly, proceed as explained in " Combustion gas probe".


information Open all water and gas blocking devices. Purge the pipes.

The front panel in the burner and pilot burner area may reach high temperatures, with risk of burning in case of contact.

Digital display - description

Digital display - description
Fig. 6 Digital display

  1. Temperature/error code
  2. Malfunction indicator
  3. Temperature measurement units
  4. Heater in operation (burner turned on)


Battery insertion

  • Insert the two 1.5 V R20 batteries.

    Fig. 7 Inserting the batteries

Replacing the batteries

The batteries must be changed if the red LED starts flashing.
Replacing the batteries
Fig. 8 Replacing the batteries

Precautions when using the batteries

  • Do not insert flat batteries.
  • Only use the type of batteries indicated.

Before starting up the heater

  • Initial startup must be performed by a qualified technician who will provide the client with all the necessary information for optimum operation of the gas heater.
  • Check if the gas indicated on the rating plate is the same as the one used at the location.
  • Open the gas valve.
  • Open the water valve.

Turning the heater on and off

Turning on

  • Press the switch , position .
    Turning on - Pressing the switch
    Fig. 9

Green light on = Main burner on
Turning on - Green diode indication
Fig. 10

Turning off

  • Press the switch , position .

Power adjustment

Lower water temperature.
Less power.
Power adjustment - Lower Water Temperature
Fig. 11
Higher water temperature.
More power.
Power adjustment - Higher Water Temperature
Fig. 12

Temperature/flow adjustment

  • Turn anti-clockwise
    Increases flow and decreases water temperature.

    Fig. 13
  • Turn clockwise.
    Decreases flow and increases water temperature.

Regulating the temperature to the minimum required value reduces energy consumption as well as the possibility of limescale deposits in the heat exchanger.

The temperature on the display is not precise, always check before bathing children or elderly people.


Heater adjustment

information * Sealed elements must not be opened.

Natural gas

Heaters for natural gas (G 20) are supplied sealed from the factory after being adjusted to the values indicated on the rating plate.

information Heaters must not be turned on if the coni nection pressure is lower than 15 mbar or higher than 25 mbar.

Liquefied gas

Heaters for propane/butane (G31/G30) are supplied sealed from the factory after being adjusted to the values indicated on the rating plate.

The following procedures must only be performed by a qualified technician.

It is possible to adjust the power using the burner pressure process, although a manometer is necessary for this procedure.

Pressure adjustment

Accessing the adjusting screw

  • Remove the front part of the heater.

Connecting the manometer

  • Unscrew the shut-off screws (Fig. 14).
  • Connect the manometer to the burner pressure measuring point.

    Fig. 14 Pressure measurement point

Maximum gas flow adjustment

  • Remove the seal from the adjusting screw (Fig. 15).
  • Turn on the heater with the power selector set to the left (maximum position).

    Fig. 15 Maximum gas flow adjusting screw
  • Open various hot water taps.
  • Using the adjusting screw (Fig. 15), regulate the pressure until achieving the values indicated in the table 6.
  • Seal the adjusting screw once again.

Minimum gas flow adjustment

information The minimum gas flow adjustment is performed automatically after the adjustment of the maximum gas flow.

Natural gas H Butane Propane
Injector code WR11
8708202113 (1,10) 8708202130 (0,70)
8708202124 (1,20) 8708202128 (0,72)
8708202113 (1,10) 8708202128 (0,72)
8708202116 (1,25) 8708202132 (0,75)
8708202115 (1,15) 8708202130 (0,70)
8708202116 (1,25) 8708202132 (0,75)
Connection pressure (mbar) WR11
20 30 37
MAX (mbar) WR11 12,7 28 35
WR14 12 28 35
WR18 10,3 25,5 32,5

Tab. 6 Burner pressure

Conversion to a different type of gas

Only use the original conversion kits.
The conversion must only be performed by a qualified technician. The original conversion kits are supplied with assembly instructions.


information Maintenance must only be performed by a qualified technician. After one or two years of use a general overhaul must be performed.

Before performing any maintenance work:

  • Close the water flow valve.
  • Close the gas flow valve.
  • Only use original spare parts.
  • Order the spare parts according to the spare parts catalogue for the heater.
  • Replace the joints and removed O-rings with new ones.
  • Only the following lubricants must be used:
    • Hydraulic part: Unisilikon L 641 (8 709 918 413)
    • Coil unions: HFt 1 v 5 (8 709 918 010).

Periodic maintenance work

Functional check

  • Check the operation of all safety, adjustment and monitoring elements.

Heat exchanger

  • Check the heat exchanger is clean.
  • In case of dirt:
    • Remove the heat exchanger and take out the limiter.
    • Clean the chamber with a powerful jet of water.
  • If dirt persists: Soak the plates in hot water with detergent and clean thoroughly.
  • If necessary: De-lime the interior of the heat exchanger and the connection pipes.
  • Install the heat exchanger using new joints.
  • Install the limiter on the support.


  • Check the burner annually and clean it if necessary.
  • If it is very dirty (grease, soot): Remove the burner, soak it in hot water with detergent and clean it thoroughly.

Water filter

  • Replace the water filter installed in the water automa- tic entry.

Burner and pilot injector

  • Remove and clean the pilot burner.
  • Remove and clean the pilot injector.

Without a water filter installed, turning on the heater is prohibited.

Startup after maintenance work

  • Tighten all connections once more.
  • Read chapter 4 "Use" and chapter 5 "Adjustments".

Heater purge

In case of a frost risk, proceed as follows:

  • Remove the fixing lock from the filter screw cap (no. 1) situated in the water automatic.
  • Remove the filter screw cap (no. 2) from the water automatic.
  • Empty all the water contained in the heater.
    Heater purge
    Fig. 16 Purging
  1. Lock
  2. Filter screw cap

Combustion gas probe

The probe must never be turned off, modified or replaced with a different part under any circumstances.

Operation and precautions

This probe verifies the conditions of flue evacuation and, in case of malfunction, it automatically turns off the heater. This prevents the combustion gases from entering the room where the gas heater has been installed. The probe restarts after a reset period.

If the heater turns off during operation:

  • Ventilate the room.
  • 10 minutes later, turn on the heater once again. Call a qualified technician if the same thing happens again.

The user must never touch the device.


If the probe malfunctions, proceed in the following manner:

  • Unscrew the probe fixing screw.
  • Detach the ignition unit terminal.
  • Replace the damaged part and proceed with its assembly using the steps indicated in the previous table, in reverse order.

Operating check

To check the correct operation of the combustion gas probe, proceed in the following manner:

  • Remove the combustion gases evacuation pipe.
  • Replace it with a pipe (approximately 50 cm long) blocked at one end.
  • The pipe must be routed vertically.
  • Turn on the heater at nominal power and with the temperature selector adjusted to maximum temperature.
    In these conditions, the heater must turn off two minutes afterwards, at most. Remove the pipe and replace the evacuation pipe.

*Maintenance and Operating Check procedures must be performed by a qualified installer.



Assembly, maintenance and repairs must be performed by qualified technicians only. The following chart offers solutions to possible problems (solutions followed by an * must be undertaken by qualified technicians only).

Problem Cause Solution
The heater does not ignite and digital display is turned off. Batteries flat or not inserted correctly, or switch turned off. Check battery position and/or replace them, check switch position.
Slow and difficult ignition of the burner. Flat batteries. Replace them.
Red LED in switch flashes. Flat batteries. Replace them.
Water at low temperature. Check the temperature selector position and adjust it according to the desired water temperature.
Water is not heated, no flame.
Insufficient gas supply.
Check reducer, and if inadequate or malfunctioning, replace it.
Check if the bottles (butane) freeze during operation, and if so, move them to a warmer place.
The burner turns off the heater is operating.
Temperature limiter has tripped (digital display shows "E9"). Wait 10 minutes and restart the heater. If the problem persists, call a qualified technician.
Monitoring device of combustion gases evacuation has tripped (digital display shows "A4"). Vent the area. Wait 10 minutes and restart the heater. If the problem persists, call a qualified technician.
Incorrect temperature informa-tion in the appliance digital display. Insuficient contact of the temperature sensor. Check and correct the temperature sensor assembling.
Digital display shows "E1". Water temperature sensor has tripped (outlet water temperature above 85°C). Reduce the water temperature using the power and/or temperature adjustment selector. If the problem persists, call a qualified technician.
Digital display shows "A7". Temperature sensor incorrectly connected. Check and correct connection.
Temperature sensor defective. Replace the temperature sensor.
Blocked heater. Digital display shows "F7" or "E0". Turn the heater off and on, if the problem persists, call a qualified technician.
There is spark but the main burner does not ignite, heater blocked. No ionisation probe signal (digital display shows "EA"). Check:
  • Gas supply.
  • Ignition system (ionisation electrode and electrovalves).
Blocked heater, digital display shows "F0". Supply (switch or battery replacement) was activated with a hot water tap running. Turn the water off and on. If the problem persists, call a qualified technician.
Reduced water flow.

Insufficient water supply pressure. Check and correct. *
Dirty taps or mixers. Check and clean.
Gas automatic blocked. Clean filter.*
Heat exchanger blocked (limescale). Clean and de-lime if necessary.*

Tab. 7

Documents / Resources

Download manual

Here you can download full pdf version of manual, it may contain additional safety instructions, warranty information, FCC rules, etc.

Download Junkers miniMAXX WR 11-2 B Series Gas Heater Manual


Need Assistance?

Do you have a question about the Junkers miniMAXX WR 11-2 B Series that isn't answered in the manual? Leave your question here.

Error while submitting your question. Please, reload page and try again.

Thank you! Your question has been received!

Table of Contents