Site cabin EICR

Imagine that somehow wiring or a fitting in the cabin fails, and the metal door becomes live, or that someone walks out the door with an extension lead that is damaged.  If someone could get between the mud outside, and some exposed live parts,  will the ADS operate without exposing the user to a dangerous voltage for a dangerous time? 

That is the killer question.

By which we mean can we manage knock off times of 230V in half a heartbeat period, (0.2 seconds)  or 110V in a heartbeat period  (0.4 seconds), or anything less than 50V more or less for ever (sub kilo-second perhaps ?)

If you have an RCD as the first thing in the line, then we can turn that round, what resistance would operate the RCD suitably fast, with a voltage drop such that no more  than 50v reached the victim. For a 30mA RCD  this is  a very easily met  50/30milli  = ~ 1600 ohms. For ADS of just a 3 amp fuse it is a less easily met 16 ohms, and for a 32A fuse or MCB with no RCD,  forget it, go and buy an RCD.


Actually a sat cabin on its skids in a puddle probably meets the 1.6 kilohm requirement with no further actions, at least until you get a few sunny days,  but a 30mA RCD may be a bit frisky in a large installation, so you may find you have 100mA or 300mA up front RCD before splitting to each final cct. (how many cabins on the genset ?) 


I'd aim for the hundred ohm mark, not from regs, there is not one,  but because it is a number easily net in all but the driest sand, where you cannot get a shock anyway, as the ground is not conductive.

Suggest you start with driving  in a 4ft rod at the genset and if need  be another at the cabin.

calibrate your expectations and
have a laugh at some real figures measured on a cabin, a large tent and a few other things.


I was a bit surprised myself, Essex is a bit more conductive than here (Hants).

Imagine that somehow wiring or a fitting in the cabin fails, and the metal door becomes live, or that someone walks out the door with an extension lead that is damaged.  If someone could get between the mud outside, and some exposed live parts,  will the ADS operate without exposing the user to a dangerous voltage for a dangerous time? 

That is the killer question.

By which we mean can we manage knock off times of 230V in half a heartbeat period, (0.2 seconds)  or 110V in a heartbeat period  (0.4 seconds), or anything less than 50V more or less for ever (sub kilo-second perhaps ?)

If you have an RCD as the first thing in the line, then we can turn that round, what resistance would operate the RCD suitably fast, with a voltage drop such that no more  than 50v reached the victim. For a 30mA RCD  this is  a very easily met  50/30milli  = ~ 1600 ohms. For ADS of just a 3 amp fuse it is a less easily met 16 ohms, and for a 32A fuse or MCB with no RCD,  forget it, go and buy an RCD.


Actually a sat cabin on its skids in a puddle probably meets the 1.6 kilohm requirement with no further actions, at least until you get a few sunny days,  but a 30mA RCD may be a bit frisky in a large installation, so you may find you have 100mA or 300mA up front RCD before splitting to each final cct. (how many cabins on the genset ?) 


I'd aim for the hundred ohm mark, not from regs, there is not one,  but because it is a number easily net in all but the driest sand, where you cannot get a shock anyway, as the ground is not conductive.

Suggest you start with driving  in a 4ft rod at the genset and if need  be another at the cabin.

calibrate your expectations and
have a laugh at some real figures measured on a cabin, a large tent and a few other things.


I was a bit surprised myself, Essex is a bit more conductive than here (Hants).