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Is there a current differential sense coil inside this ELCB (Earth Leakage Circuit Breaker) just like GFCI or RCD? I took it from a unit and I dont want to break it apart to peek I cant find any schematic in the part no. I read in wiki ELCB is based on voltage sensing, but isn't this was old 1950s tech. Modern ELCB still use it?

enter image description here

Jtl
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    I think ELCB, GFCI and RCD are alternate names for the same general type of device used in different jurisdictions. – Peter Bennett Sep 18 '20 at 00:32
  • But if you will read the internet. ELCB only protects from earth meaning if a person is between them. No protection whereas RCD can. – Jtl Sep 18 '20 at 00:45

2 Answers2

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Is there a current differential sense coil inside this ELCB (Earth Leakage Circuit Breaker) just like GFCI or RCD?

No there isn't if the device is a true old-fashioned ELCB. There will be a coil but that coil will be sensing current flow through the earth connection like this: -

enter image description here

The ELCB relies on an intact earth connection to the downstream equipment and an intact earth connection back to the fuse board. It is the forerunner of the GFCI or RCD: -

enter image description here

The great thing about the GFCI or RCD is that it doesn't require an intact earth connection to be able to infer an earth current. That's where the differential transformer plays its role.

ELCBs are old-tech now and not as safe as GFCIs or RCDs.

Andy aka
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  • I wonder why most water heaters have ELCBs and not RCDs. Any idea? – Jtl Sep 18 '20 at 06:54
  • Hmm maybe because water heaters are earthed by default hence the wire is present AND maybe elcbs are cheaper tech? – Andy aka Sep 18 '20 at 07:46
  • What happens if water heaters are not earthed? It's plastic enclosure. In my place. All tankless instant water heaters are not earthed and i have never seen one that is earthed. – Jtl Sep 18 '20 at 08:14
  • I have no idea on your country's regulations for this type of apparatus. If no earth wire then use an RCD/GFCI. – Andy aka Sep 18 '20 at 09:13
  • I bought another tankless water heater, a stiebel eltron. They used RCCB/RCD already. See https://electronics.stackexchange.com/questions/522816/why-is-there-a-fuse-in-this-rccb-rcd/522820#522820 but in their ads they stll used the term ELCB. It will be better to use the more modern RCD term isnt it. – Jtl Sep 23 '20 at 10:20
  • I'm unsure what you are asking me @Jtl – Andy aka Sep 23 '20 at 10:22
  • Just sharing they used RCD in latest models. I thought it was still old ELCD tech. I guess the industry got stuck with the old term. – Jtl Sep 23 '20 at 10:28
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The pictured device is a current sensing RCD type ELCB

enter image description here

note the trim level is given in millampreres note also the two terminals each side (in the original photo) a voltage sensing ELCB would have three terminals each side.

Kyokuto's website does not list this part, but does list some with similar part numbers. It also has this picture:

enter image description here

I doubt that this is 60 years old, the Chinese weren't making anything like this 50 years years ago. I suspect that it's now old stock from a discontinued line.

Jasen Слава Україні
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  • Its used in present panasonic tankless water heaters..so its really an RCD? Why did they call it ELCB? According to wiki entry of it. An ELCB senses the voltage. – Jtl Sep 18 '20 at 06:59
  • @jasen There is a technical difference between an ELCB and an RCD. – Andy aka Sep 18 '20 at 09:15
  • @Jtl I agree with wikipedia: "RCD/RCCB is the commonly used ELCB type." – Jasen Слава Україні Sep 18 '20 at 11:03
  • Then Wiki is incorrect. – Andy aka Sep 18 '20 at 11:04
  • @Andyaka the difference is that all RCD are ELCB but not all ELCB are RCDs. if you have evidence to the contrarary please cite it. – Jasen Слава Україні Sep 18 '20 at 11:07
  • I bought another tankless water heater, a stiebel eltron. They used RCCB/RCD already. See https://electronics.stackexchange.com/questions/522816/why-is-there-a-fuse-in-this-rccb-rcd/522820#522820 but in their ads they stll used the term ELCB. It will be better to use the more modern RCD term isnt it. – Jtl Sep 23 '20 at 10:21