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In 2017 my family moved to a new construction. Despite having three-phase power, I've noticed that all the electrical connections are on just one phase. The main breaker for this phase occasionally trips, especially if we run many appliances at once (oven, two room heaters, water kettle, and the home lighting which is almost all LCD bulbs).

  • Is it normal for all circuits of the house to be on a single phase?

  • Might I reduce the phase breaker trippings by moving some circuits to other phases?

  • I am installing a three-phase 22 kW electric vehicle charging station this week (the car is limited to 11 kW), does that change the answer to the previous question?

I am installing a rooftop solar system without battery in the coming weeks, if that has any importance. This is in Israel, we use 230 V 50 hZ household electricity. I have read this similar question but the answers discuss what is possible, with an emphasis on the NA market, but do not discuss what it typical or even best practice for a greenfield three-phase installation.

Late addition:

This is the entire panel. Unrelated to this question, one of the circuits is down because after last week's rain it is tripping the RCD-GFCI. It feeds outlets in the exterior load-bearing wall in two adjacent rooms.

Entire panel.

It appears that I was wrong. I thought that the three triple-breakers were main breakers for each phase. Thus, when only one is tripping (the one next to the RCD) and the whole house goes dark, I thought that the whole house was on a single phase. But that is not the case. Rather, that breaker is 25 amps and breaks all three phases. The 16 amp triple on the left goes to a room air conditioner, and I think that the 16 amp triple on the right is unused.

Close up of the main breaker and RCD from above:

main breaker and RCD

Close up of the main breaker and RCD from below:

main breaker and RCD

Close up of the two triples from above:

two triples

Close up of the two triples from below:

two triples

Is 25 amps really enough for the main breaker?

I do understand that it is 25 amps per phase, so that's 75 amps for the whole house. But a dozen 16 amp circuits shouldn't require a main breaker rated higher than 25 amps? I stress that this breaker pops often. I suspect that many of the heavy loads may be on a single phase, is that something that I can check? I think that using an ohmmeter with the main breaker tripped might work, but I'm not an electrician so I don't ever touch anything inside the panel without a professional.

Second edit, more information:

This is in a stand-alone home on half a dunam of land (1/8 acre) built in 2017. These are the high-load devices in the house, I do not know which devices are on which phases:

  • 120 liter water heater
  • Two 2 Kw IR bathroom heaters
  • Four 1 horsepower room air conditioners
  • One 1.5 or 2 horsepower room air conditioner for the common area
  • Cooking oven
  • 2 kW water kettle
  • Three-phase electric range
  • Washing machine
  • Electric drier
  • Dish washer
  • Vacuum cleaner
  • 2 kW portable IR heater for grandma, could get plugged into anywhere depending on where grandma is.
  • Near future: three-phase electric vehicle supply equipment
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    If a real electrician is doing the solar work, ask them about your panel. If it’s wrong, they can almost certainly reshuffle it quite easily. If it was done conventionally, they can explain why. Mar 20, 2022 at 13:26
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    What is typical may also vary with whether the home is part of a multi-unit building or standalone - in the former case if there's a 3-phase supply then balancing the loads is fully normal, in the latter case it's not uncommon for that balancing to be by putting different units on different phases.
    – Ecnerwal
    Mar 20, 2022 at 13:34
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    Thanks, I'll snap some photos this evening and post them. This is in a stand-alone home on half a dunam of land (1/8 acre).
    – dotancohen
    Mar 20, 2022 at 14:47
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    Yikes! Bare wires hanging in the panel? Even if they're not connected to anything, that's just shoddy workmanship. At a minimum they should be wire-nutted/Wago'd/something to cover the bare ends.
    – FreeMan
    Mar 22, 2022 at 16:17
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    That load shedding gizmo is pretty nice but I think the cost and effort in this case makes it a BAD idea. You need a service upgrade. The load shedder costs about 700 EUR, and it requires contactors to do the actual shedding, and you don't have room in your panel for all this. And then, if you do install it, you can't set it to 25A, you have to set it to what, 20A? Then you'll just be constantly shedding everything, full time. You may as well just turn off a bunch of things and put "DON'T TOUCH" stickers on the power switches.
    – jay613
    Mar 23, 2022 at 18:40

2 Answers 2

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25A per phase isn't very much

However, the main breaker size is decided by the wires feeding it, and the capacity of the power company's transformer. We put breakers in to protect those wires from starting a fire.

Particularly if you plan to do EV charging here, your electric service is far too small for the job. 22,000 VA is about 30A per phase, and that is not going to happen on a 25A service (though note: EVSE's are extremely modern and can be configured to a lower current rating, depending on what the service can handle).

You will need to acquaint yourself with which breakers are on which phase, which loads are on each breakers, and the current draw of each load. AKA the "Green Acres system". Make sure that no circuit exceeds its trip and no phase exceeds its 25A phase trip.

The main question will be determining which breakers are on which phase. You can do that with a quality voltmeter. Start at the main breaker at one phase. Measure to each other breaker's output terminal (it needs to be on). If you see 0 volts it is on the same phase. If you see ~400 volts it is on a different phase (no practical way to determine which).

If you prefer to do this with all breakers off and measuring continuity, that can work if you have access to the input side of each breaker. Measuring continuity with any beakers on won't work, because the stuff on the circuit will effectively short the outputs together (at low test currents).

Now, on this DIN Rail type breaker panel system, they don't have pre-defined "bus bars", and everything is just bodged together with many jumper wires (and sometimes some bus combs). That is normal for European style systems. The upside of this system is the phasing of each circuit is easy to change. So if you find yourself with an excessive number of practical loads on one phase, that can be tuned easily by an electrician.

Your questions

There are 2 major systems of electrical in the world: North American 240V center-tap (giving 120V also), and "European" 3-phase "wye" with 230V per phase (400V corner to corner).

Q1: In most Euro-system countries, the 230/400V is created at a transformer which serves several city blocks, and each house is given 1 phase and neutral. (though 2 phases or all 3 can be had).

Israel is a nation of relatively recent immigrants. It wouldn't surprise me at all if the person who wired your house came from a "1-phase" country and followed their training and habit, ignoring the other 2 phases.

Q2: Probably you can move loads to the 2nd or 3rd phase. Many larger electric appliances are certainly designed for that. In fact where 3 phases are available, this is preferred as it evenly loads the 3 phases. (Americans wonder why almost every size of tankless water heater takes three 240V circuits -- that's why.)

Q3: Can I do that with an EVSE? Maybe - but the breaker would need to have common trip. Most likely an EVSE is going to be drawing from the 3 phases and ignoring neutral - that is, it will be "Delta-connected". When a load is Delta-connected, it needs to have common trip so all 3 breakers throw if one trips. And unfortunately the "Type 2" IEC 62196 connector leaves it up to the car whether to be a wye or delta load. So you must plan for the worst and have one 3-phase common-trip breaker.

What a bad design - there was no earthly reason to bring four phase wires to an EV - if you have all 3 phases, neutral contributes nothing, and if you only have 2 phases, you only need 3 wires. EV chargers onboard the car are silicon electronic devices which dynamically limit their current draw, so they certainly can adjust "on the fly" to suit different currents and phasing arrangements.

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  • Thank you! I'm embarrassed to state that I've misrepresented the problem - in fact the main breaker that keeps popping does not control a single phase but rather it control all three phases. But your answer is informative nonetheless, I think that it should stay. I have updated the question with better information and photos.
    – dotancohen
    Mar 21, 2022 at 9:15
  • The electric vehicle charging station is 22 kW, not 2 kW as previously stated. Sorry for the confusion.
    – dotancohen
    Mar 22, 2022 at 15:19
  • @dotancohen That makes more sense, but you'll need 30A for that alone. Ain't gonna happen on a 25A service that is already tripping the main (it's very unusual to trip a main). The fact that you expect this tells me you are totally unrealistic, which to me suggests "uninformed". That's why you need the survey of loads and circuits as I discussed in my edit ... to determine why it's tripping now - is it imbalance or general overload. Note that EVSE's can be "dialed down" to use less power, so you could detune the EVSE to say, 8KW if that is the power you can spare. Mar 22, 2022 at 18:28
  • I appreciate your honesty. I do concede to being uninformed, that is quite why I posted the questions here! I would like to survey which known-heavy loads are on which phase to perhaps balance them. With the main breaker thrown, can I safely test continuity between circuit fuses to determine if they're on the same phase? With the power on, can I safely measure the voltage across circuit fuses with a common AC voltmeter to determine if they're on the same phase (I know that this is possible with 180-degree US split-phase)? I suspect this might trip the RCD though.
    – dotancohen
    Mar 23, 2022 at 8:45
  • @dotancohen I edited to correct that. It can be done like a 180-degree US panel... with the snag that if you're on an "opposite" phase, it won't tell you which one. So you'll need to make a second pass. Continuity will only work if you have access to the supply side of the branch circuit breakers - but if you do, you can simply look at the wires or combs. Mar 23, 2022 at 17:11
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To your last question

There is no need to repeat the good content of Harper. I just want to answer your last question.

You cannot balance the phases with an ohmmeter. The professionals do it by measuring the current with a clamp meter, on the live circuit.

Most of the time that won't even be necessary, as the average electrician has a fairly good idea on how the loads are distributed by just looking at the circuits..

Update

I expect the distribution of the phases to be like this: enter image description here

Update, response to your comments

You can of course verify the phase distribution with an multi-meter:

  • Switch off the main breaker.
  • Switch off all of the individual circuit breakers (the "leaves", so to speak).
  • Verify that there is no more tension.
  • Don't touch or probe the hot side of the main breaker.
  • Use a suitable device (600V CAT III device or superior)
  • Test for continuity across the different phases.

If you feel confident enough to work on the live panel, and have a suitable device (600V CAT III device or superior) you can also measure the tension across the breakers. Please note that 400V is to be taken seriously.

If the tension across the breakers is at about 400V, the breakers are on a different phase (yes, 120° degree). If the tension is 0V, the breakers are on the same phase.

Since you can verify the phase distribution with the main breaker off, I'd recommend to take the safe way and test just the continuity without working on the live panel.

Small comment upon the grounding errors

I don't know your local electrical code, but one RCD for the entire panel strikes me as the bare minimum. Maybe one RCD per row would be better, but requires extensive alterations (one neutral bar per RCD)

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    Good point .... if the breakers are labelled an experienced electrician would be able to quickly tell you if rebalancing is likely to solve your existing problems, without measuring anything. Those panels usually have labels in the space between the rails. I can see the tabs where the label panels would mount. Did you remove them for these pictures? Do they exist?
    – jay613
    Mar 21, 2022 at 22:09
  • Of course I won't be able to balance the phases with an ohmmeter, but if I see that e.g. the water boiler, oven, induction range, and resistance heater are all on the same phase then I could maybe move one or two high-load devices to another phase. I don't expect to actually measure the loads, rather I already know what the high-load devices are.
    – dotancohen
    Mar 22, 2022 at 7:26
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    @dotancohen oh, I understand you now. I updated my answer
    – Martin
    Mar 22, 2022 at 8:39
  • Yes, I would expect that too, with the caveat that the second row might be shifted left. But honestly, there have been other electrical problems in this house, such as a ground fault that you can see as one of the breakers is down (The RCD pops if I raise it). I suspect that the electrician did just the bare minimum to pass the eyeball inspection and I'd like to check the phasing.
    – dotancohen
    Mar 22, 2022 at 9:25
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    I see that I didn't answer your first question. You are correct, I removed the label panel to photograph the panel. When we moved in the labels were all blank, but I've been filling them in over time.
    – dotancohen
    Mar 22, 2022 at 10:02

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