First of all this is the technical data written on the heater: enter image description here

I've been using the following connection for my water heater for 2 years before the switch key got molten as shown in the following two pictures ( The heater was always left in the socket and we used the switch key for turning the heater on/off ): enter image description here enter image description here

Now, I called for an electrician and he replaced that connection with a breaker of 30 Ampere. As far as I know, A heater like this won't use more than 7 ampere, so I believe it's better to replace it with 15 ampere or something like this.

enter image description here enter image description here

My question is:

Am I correct that this breaker isn't functional ?

Can this connection cause any damage if I didn't change it ?


This is the main breaker of the home enter image description here

EDIT 2: The water heater is connected to that C20 breaker with some 7 bulbs of 16 watt each and some times we connect 2000 watt device, so this whole circuit uses about 16.4 Amp. The main circuit breaker of 20A is perfect in my opinion, but still want a perfect connection for the heater itself. Now: What connection is better ?

  1. The old connection but with replacing that 30A switch-breaker with 10A one ?

  2. The new connection as it was, not grounded because no ground sockets in Egypt.

  3. Something else is better ?
  • main breaker of the home which one is for the Water heater circuit ?
    – Ken
    Jan 22, 2018 at 10:56
  • When switching electrical loads that are energised I usually want 2× the current rating. As the voltage gets higher like 480 it requires disconnects that can handle the arcing or the life of the switch will be very short.
    – Ed Beal
    Jan 22, 2018 at 15:02
  • @Ken Can you assume both brakers, the one on which it's written C10 and the other which is C20 ? because I've some working devices I don't want to stop by testing the brakers one by one. Also does 10 and 20 refers to amperage or it's something else ?
    – Youssef13
    Jan 22, 2018 at 18:22
  • It looks like the actual fault that occurred here is that a bad termination failed. No overcurrent-based protection is going to detect this, nor is ground fault, and arc fault isn't required in most of europe AFAIK. This is either bad labour or bad goods. Jan 23, 2018 at 9:02

3 Answers 3


In North America, we have a service panel containing a main breaker which protects the whole panel and a row of circuit breakers which clip into buses and protect individual circuits. Europe has the same function, with breakers all in one location -- but they use random components mounted on "DIN rail" and hand wire all interconnections (no buses).

My guess is your C50 is your "main breaker" which feeds all the others, and then the 10 and 20 amp breakers protect individual circuits, presumably including the water heater circuit. I see 1-2 empty holes in your panel, so you have spare spaces. Let us try a hypothesis, that the water heater was not breaker protected at all: if so, why would they not simply use one of the spare spaces in your panel and an ordinary breaker? Therefore I suspect your water heater is protected by one of these breakers.

Therefore it is protected by 3 breakers: the 50A main, the 10 or 20A branch circuit breaker, and the 30A standalone switch-breaker. You should really study/follow the wires to make sure of that assumption. Or you could turn off the 10/20A breakers one at a time to see if any of them power the water heater.

It really doesn't do any harm to have redundant overcurrent protection. But it doesn't do any good, either. The protection will be the breaker of smallest capacity rating.

It is also possible that this switch-breaker does something special, like provide GFCI/RCD protection. Though I would expect the package to mention that.

Your electrician may have been thinking about your future. 1500W is a very small water heater that will be slow to recover. I can't speak for the rest of the world, but North American practice is to use a higher capacity water heater in the 5500W / 23A range. As Ken discusses, we derate by 125%, so 23A becomes 28.75A, fitting just inside the 30A we typically allocate for water heaters.

However in your house with a 50A main, a 30A water heater is too much. Was your electrician aware of any future plan to upgrade service?

  • The rest of the world Europe included is generally smaller appliances - less water storage / water recovery for heat as well. Just like homes and cars - everything in USA is generally bigger than the rest of the world..
    – Ken
    Jan 22, 2018 at 10:41
  • 1
    There absolutely can be busses in European panels. Comb bar is common for single-phase installations, though it is available for three-phase systems too, and pan assemblies (much like a US panel except for DIN breakers) are common in larger commercial three-phase installs. Jan 23, 2018 at 8:13
  • @Ken I live in a 400ft apartment in Hong Kong and I deliberately got a 57L 6000W water heater on a 32A circuit. It really depends on the personal choices and whether you understand how the heater works. We have a mini sit-in bathtub that the tank just perfectly have enough water to heat up.
    – Nelson
    Dec 19, 2019 at 1:54
  • 57 litres, that's amazing, you must be able to take showers for hours. Our 30 gallons don't last 20 minutes. unclear on Metric system Dec 19, 2019 at 3:56
  • 1
    @Harper-ReinstateMonica a liter is about 32oz, so 4 liters around a gallon - 57L about 16 Gallons.
    – Ken
    Dec 20, 2019 at 8:54

NEC Code 210.20 Overcurrent protection for continuous loads must be sized at no less than 125% of the load So you take that 6.8 Amps (or lets just say 7 Amps and multi ply by 1.25 = 8.75 So a 10 AMP breaker would be MORE than sufficient. A breaker higher rated than this - what do you prefer to burn up first the Water heater or trip a breaker.

Your water heater manual SHOULD specify the manufacturers recommended breaker. Just doing my calculations based on code if the Water Heater is the only thing on that circuit - then I would Reduce the breaker to a 10 AMP circuit and protect the water heater.

  • okay, Now I knew that 30 AMP won't protect the water heater, but can it cause a damage ? How can I know if there is anything else on that circuit ?
    – Youssef13
    Jan 22, 2018 at 9:54
  • @Youssef13 - if it will not protect it - it will cause damage by not tripping soon enough. BTW the NEC code is for USA; I notice your WH has 50HZ power - Where in the world are you located ?
    – Ken
    Jan 22, 2018 at 9:58
  • What about my previous connection, Was it protecting the heater ? I'm in Egypt.
    – Youssef13
    Jan 22, 2018 at 10:00
  • @Youssef13 you never state what was there for previous connection, as for the amperage nor does your picture make that clear either. Please state that or post a picture of it. (In the USA a breaker is not used to turn a device on or off - this will wear out the effectiveness of the breaker to perform as it should) so we either leave the unit on all the time or we have a power switch to turn the unit on/off.
    – Ken
    Jan 22, 2018 at 10:38
  • to be clear about my previous connection: On the switch key it's written: 10/250~ On the socket it's written: 16A 250V~ I just want to know if the previous connection was better and effective.
    – Youssef13
    Jan 22, 2018 at 10:49

30A for a 1500W appliance is too big (In this case is your boiler that 'protects' the braker), just go for a T7A (slow-blow fuse), water heater is a resistive load and doesn't have a big start up overcurrent. So keep the fuse little.

If your fuse breaks too often consider going for a 10A but no higher

Also suggest (if not yet done) to use a proper socket and not to force a schuko a regular receptacle. Your (old) connection was also un-grounded and you're at risk of being electrocuted while taking a shower

  • If by ground you mean that socket with 3 holes, It's not in Egypt at all, so in that case, is replacing that breaker with 10A with the same connection is better or the old connection is better , or there's better than both of them ?
    – Youssef13
    Jan 22, 2018 at 18:17
  • @Youssef13 The new connection appears to be stripped back to far (can just see inner cores poking out from behind the plate), and has no strain relief. IMHO this would be much worse than your previous install. The right answer is either a grounded socket or a proper permanent flexible cable connection. Jan 23, 2018 at 9:05
  • @SomeoneSomewhere There are no grounded sockets in Egypt as I mentioned in my previous comment, so replacing that 30A breaker with 10A with the same connection is better or the old connection is better , or there's better than both of them ?
    – Youssef13
    Jan 23, 2018 at 10:01
  • Note: I don't think ground will be important as we turn off heater switch before we go shower.
    – Youssef13
    Jan 23, 2018 at 10:06
  • I Suggest: Permanent wiring (with ground connected) and a 10A braker. Or buy a couple soket/receptacle (type F or L) that can carry the ground for such kind of appliance. A fuse is recomanded.
    – DDS
    Jan 23, 2018 at 12:22

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