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I want to replace my current electric stove that's powered by a single phase line with a 20A fuse. I'm in Germany with 230V AC. The overall power that can be delivered is 20A*230V = 4.6kW.

I'm looking at radiant electric stovetops. Some of the new electric stoves I look at come with a power rating of 7kW or even 10kW (oven and top combined). Many can be attached to 1-phase or 3-phase lines. The connector panel on the oven is configured for 1- or 3-phase with metal bridges which connect the three phase terminals in the case of a 1-phase line. Here is a typical schematic where the left side is configured for single phase: connection schematic 1 phase vs. 3 phase

My question is basically: Since the single phase line cannot deliver the 7, let alone 10 kW, the stove must operate differently in a way I don't understand. The stove consists of a number of "consumers" which are essentially independent (the four burners plus oven plus grill). They are probably ohm's resistors (as opposed to induction ovens). My questions are:

  • Does the oven start to reduce consumption only when operating several consumers at the same time would exceed the rating (supposedly, it would be limited to pull no more than 20A from single phase)? (Reduction could be by alternatingly switching the burners on and off or by reducing constant output.)
  • If yes, how is that achieved?
  • Or does it already work with reduced power on a single burner? That would affect all cooking.

The latter would automatically happen if the burners were driven by phase-to phase 400V in the three-phase-configuration but the normal phase-to-neutral in the 1-phase configuration, provided they are essentially ohmic resistors: A burner would never be able to operate at its nominal maximum rating but instead max out at a fraction of it.

But the fact that the three phase connectors are shorted in the 1-phase configuration makes me think that the burners cannot be driven by phase-to-phase power, unless the shorting is detected and reconfigures the wiring.

Essentially, this question boils down to a pragmatic one (how does 1-phase affect my cooking) and a theoretical one (how does the oven work?).

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As you can see, the 2-phase solution is specified with 4mm² wires while the 3-phase solution is specified with 1.5mm² wires. For wires on a wall, that corresponds to 36A vs 17.5A of maximum permitted current (the 17.5A is for 3 carrying wires).

So with your installation, it seems most likely that 1-phase will affect your cooking by triggering the breaker. The desired stove will not likely run on a single 20A line. The wiring spec strongly suggests that three-phase vs one-phase will not load the lines differently.

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  • \$\begingroup\$ In a wall, German specifications appear to indicate 23-26A for 4 sqmm (p.145). \$\endgroup\$ Commented Oct 28, 2023 at 11:12
  • \$\begingroup\$ 3-phase ovens are used from 1-phase all the time. They are designed to do that. It needs more amps over L - N than L1 - L2 - L3, and it's slower, that's the real drawback. \$\endgroup\$
    – MiNiMe
    Commented Oct 28, 2023 at 11:31
  • \$\begingroup\$ @Peter-ReinstateMonica Wires don't come out of a wall. The specs for the wires are for the connection from access point to oven. The access point is rated for a certain current, and it is the job of the electrician wiring the building to ensure that the in-wall wire is good for the access point specs and corresponds to the breaker. \$\endgroup\$
    – user107063
    Commented Oct 28, 2023 at 14:12
  • \$\begingroup\$ @user107063 Ah, I was not aware that there may be an "access point" on the wall and a different cable from that to the stove (I have not taken it out far enough yet). \$\endgroup\$ Commented Oct 28, 2023 at 20:42
  • \$\begingroup\$ I was also pondering over the fact that the current stove most likely has a higher rating as well but has never triggered the breaker. In all reality we probably only ever use all burners + oven for Christmas or Thanksgiving (I have an American partner), and then we don't max them out but there's something simmering on one or two so that the burner is on on maybe 20% of the time, the oven is probably running at 50% or 60% for the goose or turkey and not using the grill, so that we stay below the limit, and the slow fuse bridges the occasional "bad timing" peaks. Interesting. \$\endgroup\$ Commented Oct 29, 2023 at 8:08

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