Testing a 50+ year old installation I found a Ze of 0.56 ohms. What I the main earth wire (which is a 6mm^2 wire but hey it's 50 years old, and it's using the earth bar in the fuse box as the MET just fyi) disappears into the wall cavity behind the fuse box and my original suspicion was that it went to an earth spike somewhere (based on the knowledge that another house of a similar age down the street is using TT). However I'm surprised to see just 0.56 ohms on a 50 year old TT system, I was expecting a lot more than that. The whole area around the house is concreted over plus paving over most of the concrete, so my fruitless search for an earth spike doesn't mean there isn't one hidden under there.
Could it possibly be a TN-S with a high reading? If so would the DNO have record of this and would they do anything about it? It's not PME, and it's in the EDF area.
Or should I forget about it and suggest sticking an RCD (in a separate insulated unit) in before the fuse box just to be sure?
Or if there's any other ideas please have a say.
Could it possibly be a TN-S with a high reading? If so would the DNO have record of this and would they do anything about it? It's not PME, and it's in the EDF area.
Or should I forget about it and suggest sticking an RCD (in a separate insulated unit) in before the fuse box just to be sure?
Or if there's any other ideas please have a say.
