I have a few 400v appliances with 5 pin plugs (pressure washer etc.) but no 5 pin plugs. I would like to easily add a 5 pin 400v socket to my existing fuse boxes, but I only have two breaker spaces left on my sub-panel.

I have found some good instructions online for adding sub-panels or 400v 3 phase sockets via a 4 pin fuse and then a 3-way circuit breaker (see photos below), but I don't quite understand how to connect this from my existing circuit board, particularly considering there are only two circuit breaker spaces left.

4 pole fuse


3-way circuit breaker

To connect to this space somehow?

Available 2 space gap


Option 1: Adding new Fuse in 2-space gap (Preferred option)

Option 1 Question: - Can I fit a 2 pin fuse (or whatever fits in the available space) and then wire it to the 4 pole fuse pictured above? If so, can you suggest how I can wire something in this two space gap without adding extra capacity to an existing fuse?

Option 2: Somehow reworking an existing fuse/collection of circuit breakers to just slip in a 400V socket to the existing generous 35A/50A fuses

Option 2 Question: - Confusingly, there is a three pin campervan socket wired with a fat wire to a ciruit breaker with a '3' symbol written on it. In the pic below youc can see this fat wire at top of pic with black, blue and earth wire going to 3 locations in fuse box. I don't understand this.

I could only get 230v out of the socket when testing with a voltometer. Could this somehow be better wired to become three phase?

3 phase circuit breaker?

Fat wire at top of pic can be seen with black, blue and earth wiregoing to 3 locations? Don't undertand this...

Confusing existing campervan 3 pin socket

Useful info:

The electric meter is rater for 400A

The existing fuses are all 35A or 50A

Most of the existing circuit breakers are capable of both 230V and 400V (I'm in Germany).

Here are some extra pics you may find useful:

enter image description here enter image description here


  • I'm no electrician so may have some of the terminology wrong.
  • Any advice/discussion is for learning purposes and I act on it at my own risk, so please feel free.
  • More pics/info available on request (max 8 allowed in this 1st post :( )
  • I appreciate any input : )

Extra photos now I have the 'reputation' to allow me more than 8 photos:

Thick wires can be seen going from meter to main panel:

 Thick wires can be seen going from meter to main panel

These Same wires (in a split grey PVC housing) can be seen going from left to right panel at the top here:

Left to right panel joined with four thick wires

Neutral and ground on top rows of left panel (joined) and seen travelling to right panel:

Neutral and ground on top rows of left panel and seen travelling to right panel

Ground and neutral on right panel (not joined):

Ground and neutral on right panel

The path of the brown and black wires on the right panel is less clear to me: The path of the brown and black wires on the right panel is less clear to me

But the black and brown wires are in some way connected to a number of fuses and circuit breakers, which I think means they are all ultimately connected directly to the electricity meter power source?

brown and black wire connections on right panel


brown and black wire connections on right panel 2

  • Those are din rail spots each breaker is hard wired to the power source. You really need to understand what you are doing, I don't usually say this but get some help. We have no idea wht type of system you want to tie into delta or Wye and there can be additional safety factors you need to know about. This looks like a industrial panel to me not a home DIY project.
    – Ed Beal
    Commented Oct 27, 2017 at 18:24
  • 1
    I'm voting to close this question as off-topic because looks like an industrial control panel not a home system.
    – Ed Beal
    Commented Oct 27, 2017 at 20:53
  • Hi Ed, This is the fuse box in a shop/flat unit in a residential building that I live in. People have always lived and worked in this property, so the fuse-box reflects that mixed usage. It is a DIY home project because I am DIYing it in my home. I am getting some very helpful hints from others, so I vote to keep it open and look forward to your input and collaboration on other posts. Best, Paul Commented Oct 27, 2017 at 21:56
  • Is one of these panels fed from the other panel? E.g. Is the right panel fed from the left panel? I.e. A subpanel of the main panel? I see 35A fuses(?) in both left and right, and wonder if one feeds the other. Commented Oct 28, 2017 at 18:19
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    @EdBeal, that's what residential breaker panels look like in much of Europe.
    – Nate S.
    Commented Feb 12, 2020 at 20:37

2 Answers 2


When you're out of room, you add a subpanel. Relocate 3 or 4 of the breakers from the current main panel to the new subpanel to make room for the new high amperage 3 pole breaker you're going to need to add to it.

  • 1
    Hi Jeff, Thanks for your input. The problem with your suggestion is that the breakers are all allocated for plugs etc as far as I can tell (they are not very well labelled). Is there a way I could use the two available slots somehow? Cheers, Paul Commented Oct 27, 2017 at 20:27
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    @PaultheDIYMonkey you're misunderstanding the advice. A subpanel is another panel with space for many more circuit breakers. When you remove breakers from the existing panel to make the needed space, you subsequently install those breakers for the removed loads into the new panel. Commented Oct 27, 2017 at 20:49
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    @Jeff: Oh, thats a great idea to surface mount the Grasslin. I'm not really sure what purpose that serves as nothing is on a timer. So, I can just extend the wires for the Grasslin to any nearby suitable place on the wall? Thanks Harper: I see what you mean about reallocating the breakers. Great, so now that space has been successfully cleared for the new 4-pin fuse, have you got a good link for instructions for how to wire up the 4 pin fuse to the power source? : ) Commented Oct 27, 2017 at 21:22
  • 1
    Why are more people not upvoting this? Good answer from new contributor. Those first few points count the most! Commented Oct 28, 2017 at 15:35
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    Still to me this is a collection of din rail breakers not a panel that most of us have seen unless working on panels for industrial locations. I have large welding outlets and connections in my shop but have not seen this kind of panel other than in a multi family dwelling in the UK when I was there to work on systems for HP. As I said it is d din rail system hard wired breakers looking at it on my computer makes me think the o.o should get some professional assistance thus my vote to close but I could down vote if a vote is needed
    – Ed Beal
    Commented Oct 28, 2017 at 20:38

I think you really need to look for advice from people more familiar with German wiring, this site is mostly populated by Americans, whose electrical standards are totally different from those in Europe. I'm a brit which is closer but still not the same.

A three phase system has three phase conductors that are out of phase with each other by 120 degrees and a three phase load must be connected to all three of them. On a normal European system you have 230V from phase to neutral and 400V from phase to phase.

Your board appears to have the breakers grouped by phase. That is fine if all the loads are single phase, but it is problematic if the loads are 3-phase as it means you can't easily achieve common maintenance shut-off or common trip, both of which are at least highly desirable (whether they are required by German regulations I cannot say).

I also see a mixture of fuses and circuit breakers, it is not clear to me from the photographs if the fuses are for different circuits from the breakers or if the fuses are in-line before the breakers. I even see blue wires going into fuses, which makes me worry that you may have fused neutrals, which are a very bad ides if you are feeding three phase loads (and may be a no-no even for single phase, again i'm not an expert on German rules).

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