This popped up last evening on that Thailand based forum of which I'm a member.
A little background.
Thailand is nominally 220V (Phase-Neutral) 50Hz, supplied as 3-phase 4-wire TNC-S with a local earth rod, neutral earthed at every 3rd pole, N-E link in the consumer unit. Supply is invariably aerials with the "weatherproof" meter on the power pole outside your gate.
OP
"Hi,
I have just noticed that the area where my earth rod is is now very hot.
Unfortunately it is under a tiled floor below where the safety cut is. It has been in place for several yeas with no problems.
we recently had improved mains and a new meter. We also recently had earth rods installed for each of the 2 showers.
Anyone any ideas?
Many thanks in advance"
A couple of members noted that this was very possibly a L-N reversal at the meter particularly as there had been work done fairly recently involving a new meter. The member was urged to call the electricity authority (PEA) urgently as this could be potentially lethal.
Next morning:-
"Thank you everyone for your help and concerns.
PEA confirmed reversed LN and corrected.
Discovered that the safety cut doesn’t work -next job- he didn’t seem concerned about the earths to the showers, he did do a stray voltage check on them though. Before voltage after reversal nothing. In addition the case of the distribution board was live or at least enough to give a powerful tingle.
Looking forward to seeing my next meter reading. "
I've seen L-N reversals many times here, always on the older TT supplies. I've never seen a TNC-S supply get swapped and the sparks not notice!
The OP timed his meter at 24 seconds per revolution with the main breaker OFF! That worked out at about 900 Baht (about 20 Squid) a month that he had been paying to warm up his kitchen floor!
The "safety cut" (actually Safe-T-Cut) is a whole-house RCBO usually installed as a retro-fit on older installations. Older units have a "Direct" or "Bypass" mode that disables the RCD section to "get the power back on in an emergency"!
The trials and tribulations of living in a tropical paradise!
