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| My first scope is arriving but my home (old) doesn't have mains grounding |
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| Jeroen3:
Does a GFCI also interrupt on broken ground or neutral? Since you all have a ground wire connected to it. I've never seen a RCD in a european store with a ground wire or terminal on it. Is that an extra feature required by code? Since broken ground or neutral is very rare here with all underground wiring. |
| Mechatrommer:
it should as per wiki i linked and from logic thinking of how it is constructed, any current imbalance will create non zero magnetic field and open the elecromagnetic coil circuit inside it, it alone doesnt required ground to work, ground wiring is imho only for double fold safety for current return path safely to earth in case wiring fault downstream such as live wire broken inside appliance and touching exterior body. with earth wiring, current flow to ground, gfci tripped, if no earth wiring, no current flow, gfci not tripped, the exterior body just float on mains potential waiting for somebody to touch to complete circuit for current to flow back to earth. without earth wiring, human body is the only mean for current to flow, but if there is earth wiring, both will share the current, either way, as long as there is current lost (non zero net) inside gfci, it will tripped, such as when a person touch bare live line (no appliances needed), i accidentally tripped gfci this way several time, never it tripped due to appliances fault (live touching metallic body) because i think products design are robust enough or i got lucky to not have shabby one hung low items in the house. not sure why is this difficult to be understood that it has to be explained several times. otoh, broken wiring is another matter, gfci should not be blamed for that. ps: why gnd wire is connected to neutral uptream gfci? to create low impedance path to ground localized to that house/area in case neutral line got raised in the middle by lightning, short on the pole or whatever (i've seen corona short somewhere, real magnificent!). by right neutral line is earthed back in the dist transformer, if not, the contractor who installed it should be blamed (at least in our country). if someone installed ground wire to neutral downstream the gcfi, thats why gfci probably not tripped in case electric shock, the current will flow from human to earth back to gfci downstream back to gfci, no current difference, net is zero, gfci will not tripped. |
| Jeroen3:
Your GFCI are dual throw and short downstream to ground? I know this is how it can work on high voltage, but for low voltage is a bit weird... |
| Mechatrommer:
--- Quote from: Jeroen3 on August 16, 2019, 10:00:32 am ---Your GFCI are dual throw and short downstream to ground? --- End quote --- no! dont do that i already explained that just before :palm: it should be upstream ie before the GFCI to your lab. if you look at reply #21, following mains supply from right to left, earth wiring is connected to neutral before the GFCI, ie after the isolator (the big CB, high current trip for all distribution smaller CBs, leftmost white component in Fergo diagram reply #39) but i dont check inside of my switchbox, whether it should be after or before isolator. i think its better after the isolator since everything (LNE) will be disconnected when isolator is tripped. what is certain, is NE connection should be before GFCI (RCCB). someone may check their certified switchbox to see at which point E and N is connected together. GFCI only for mains supply 110-220V, for non lethal low voltage you dont need any of that. |
| Jeroen3:
I asked why an GFCI's has a ground terminal. Not why the distribution network has a neutral-earth bond. That is obvious. I recently developed an automated tester for IEC 61009/62423 RCD's, and a ground terminal on an GFCI is not something I have seen before. |
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