I'm trying to understand an issue my electrician has flagged up but have been finding conflicting information online. I would ask my electrician but he's flagged anything that doesn't meet current regs as "potentially dangerous" (which is nonsense when it would have met the regs in force at the time of installation). But I digress...
He's noted a high impedance on the main earth of 119Ω. I've seen some suggestion that such a high impedance may prevent protective devices from operating as sufficient voltage won't flow to earth. Which makes sense.
It's a TN-S system. There are no RCDs but there is a voltage operated ELD. Wikipedia says that VOELDs are designed for environments with high earth impedance (though it doesn't quantify what "high" means), hence my confusion.
I will get this properly investigated, but I want to understand the issue and figure out whether this needs to be sorted ASAP or whether it can wait a few months (when I'll be getting the CU replaced).
He's noted a high impedance on the main earth of 119Ω. I've seen some suggestion that such a high impedance may prevent protective devices from operating as sufficient voltage won't flow to earth. Which makes sense.
It's a TN-S system. There are no RCDs but there is a voltage operated ELD. Wikipedia says that VOELDs are designed for environments with high earth impedance (though it doesn't quantify what "high" means), hence my confusion.
I will get this properly investigated, but I want to understand the issue and figure out whether this needs to be sorted ASAP or whether it can wait a few months (when I'll be getting the CU replaced).