Problem: when I connect the electricity fuse, a continuous alert goes off and the display errors with 4U00 (photo below) which according to the manual means the hob installation is not correct. How to fix this problem?

More details: I moved to a new apartment which did not have any kitchen, and hence got a Bosch oven and hob among other things. The oven has a normal plug which I did not have any trouble connecting.

The hob however has a 5-wire cable. The cable needed to be installed to to both the hob and the wall/electricity source manually, which I did based on the color with a one to one map, the photos are as below. Now when I connect the electricity fuse, the problem above occurs.

Update 1: We are in Germany and the product is Bosch, which have the same standard. Also added the two last images from the manual.

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

  • Usually those devices come with a wiring diagram showing which wire is which, different countries might have different wire colour meaning. Your country and the country of the hub placed in the question should help.
    – crip659
    Commented Nov 27, 2022 at 16:16
  • @crip659 Thanks I updated and added the relevant info Commented Nov 27, 2022 at 16:32
  • have you contacted Bosch technical support?
    – jsotola
    Commented Nov 27, 2022 at 17:28

4 Answers 4


If anything I mention makes you uncomfortable, or you feel like you don't know what I'm talking about, or what are you supposed to do- I would suggest paying an electrician to connect your stove, as you are dealing with electricity, and failures may be costly if not lethal.

There is some common misconception about cooking hobs which comes from the fact that people call them three-phase, and single-phase, where in fact they are mostly single phase (you can see it at the connection diagrams, which "accept" only 220-240V). You can supply them with two conductors to split the load between separate phases, but you can bridge connection terminals, and it will work on a single conductor (which can be seen in the middle connection schematics).

First thing to check - make sure that your apartment (and the wall socket you showed) is indeed supplied with 3-phase voltage. (go to the end of this post for explanation)

Second - seeing you are from Germany I would assume that wiring is done with some common standard for European Union (i.e. IEC_60446) which means that wall socket is not wired correctly, but if they are color-coded correctly and you stick with color coding for wires you'll be good.

If you indeed have a three-phase connection, your to-go schematic (from your photos) is the most left one. The error probably comes from the fact that you connected a 230V hob to 400V on at least one "internal" circuit (which I'm afraid might have fried it).

How to connect it in case of three-phase supply:

  • Green-Yellow- you leave it as is
  • from Black, Brown, and Gray you pick TWO and connect one of them to terminal 2, and one of them to terminal 3. THIRD ONE REMAINS DISCONNECTED (and should also be disconnected at wall outlet to prevent any shorts)
  • there should be a bridging bracket (basically a piece of metal) supplied with the cooker - you bridge terminals 4 and 5 and connect Blue to one of them.

How to check if you have three-phase supply (and if wiring is correctly color coded): You will need a volt-meter, with capability of measuring AC voltage. You set the voltmeter to 600V AC measurement. You probe the Gray, Brown, and Black wires in pairs - each pair should give you a reading of around 400V You probe Blue with (one by one) Gray, Brown, and Black - you should get around 230V each time.

  • Thanks, I removed the gray wire and connected 4 and 5 in hub connector and it works. I think as the instructions also say my hub only needed two phase instead of three Commented Nov 29, 2022 at 8:56

I struggled with a similar stove from Siemens. Since you are in Germany, I think the options are:

  1. you have a 2N/2L service, but that would typically come with a Perilex wall connector, which doesn't seem to be the case.
  2. you have a true three-phase service
  3. you have a 3x16A service (one phase)

You should check with a volt meter, but since you mention that your groups have separate breakers, I suspect that case 3 applies. If you have 3-phase, you should also have 3 main breakers in your box.

Please check with a volt meter!

Case 3 is missing from your instructions. I've attached the instructions from mine, which are similar (identical as far as I can tell even), and note that you need to

  • connect, on the stove, 4 and 5 together (the stove should come with a little bridge connector for that
  • connect each of the live wires to 1, 2 and 3

You don't have power on connector 1, which would explain the error message.

Excerpt from Siemens stove instructions.

excerpt from Siemens stove instructions

  • Thanks indeed case 2 is my case, which I had to cut the gray from socket and the hub connector and now it works Commented Nov 29, 2022 at 8:54
  • Although your answer is also correct, I accepted another one as they answered earlier in terms of time Commented Nov 29, 2022 at 8:56

The installation in the wall outlet terminal looks like a normal 3 phase system.

How to check it: If there are 3 phases for the range, the breaker in the panel must be a 3 phase type, i.e. must have 3 ingoing and 3 outgoing wires with colors

Black Gray Brown

on at least one side (ingoing and/or outgoing).

All those 3 phases will be switched simultaneously, if one phase has a short or draws too much current, always all 3 phases will trip. Most likely there will be one (bridged) handle for three breakers.

In that case, the gray wire is one of the three phases and must not be connected to Neutral.

There should be diagrams for an installation in a 3 phase system as well.

There are always 2 different choices for a 3 phase connection:

Case Star: Neutral needed

Case Triangle: Without Neutral

Case Star is more likely here.

Normally the upper right screw would be connected to the third phase, i.e. the gray left lower cable in the range has to be shifted to the right upper (unused) screw.

But of course, this must be confirmed by documents of the manufacturer before any work. A call would be a little bit risky (misunderstandings, unskilled/unmotivated/unconcentrated call center service personal etc.).

If confirmed, most likely the configuration for Case Star would be:

Left screw column ...... right screw column

green/yellow.......... gray



For Case Triangle, the Neutral = Blue wire must not be connected and must be isolated and secured in order to avoid any contact, f.e. in a Wago clamp.

Since ranges draw much power, a 3 phase connection is often an option.

All above is only valid in case of a 3 phase connection.

In case of a 2 phase connection (instead of 3), a change in the wall outlet and the range both is necessary:

Wall outlet: The gray wire going to the range needs to be shifted to Neutral, i.e. to the clamp with the 2 blue wires if possible and allowed with that type of clamp by the manufacturer of that wall outlet. Another option would be a double sleeve.

This would result in two blue and one gray wires electrically clamped together in the wall outlet.

In the range a bridge (should be part of the range's accessories) must be added between the left column middle and lower screws = blue and gray wire as shown in the diagram.

In other words, the Neutral path would consist of 2 parallel wires in the 2 phase case: blue and gray.

  • Thanks a lot for the detailed explanation. You mentioned that all the three phases need to to be switched simultaneously, which I am not doing at the moment, I turn on the three fuses one by one, maybe that is the problem? In this video they have mentioned a DP cooker switch, do I need one? youtu.be/WumOQq8ekWA?t=215 Commented Nov 28, 2022 at 9:42
  • Couldn't see the video yet, but if the wall outlet is provided with 3 phases (L1, L2 and L3), 3 separately switchable breakers are against code, are not allowed since many years. 3 phase appliances must always be provided via a special 3 phase circuit breaker as described in order to assure exactly 2 status: either all phases are connected or no phase.
    – xeeka
    Commented Nov 28, 2022 at 15:03

I suggest you have just matched color to color in that wall plate connection.

I think you need the blue and grey connected together based on the diagrams showing that it is either 2 live or phase with neutral as blue and grey.

However, I seriously suggest you get a professional at this point since if you get the combination wrong then you will get a bang and be buying a new one.

  • Fortunately, Bosch have a very good protection against wrong wiring, so if the OP got the U400 message, it's most likely fine. However, it's not fine to experiment with this sort of a thing if you don't know what you're doing...
    – yo'
    Commented Nov 28, 2022 at 21:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.