PME earthing to a group of static caravans TT earth required?

In terms of the regs, maybe not, as static caravans are not explicitly mentioned. But you should ask is the risk the same - the problem with a PME system generally, and this is true for car chargers garden sheds and containers / portakabins, and barns in farm yards, that the PME ' earth'  is not quite at the same potential as the true terra- firma earth, and this can lead to discomfort tingles if the user has simultaneous good contact to bare earth, or something at bare earth potential, and something at the PME earth potential . Also under network fault conditions, the PME 'earth' can be at a significant fraction of the phase voltage, but indoors in the dry, who cares, as it is all bonded, and goes to the same high voltage, and no shock is felt.


So we should ask is this a problem for this case - can someone touch the PME earth on the caravan door frame perhaps, while also touching the true ground with their feet ?

Professionally, I'd not worry about things that are seldom touched and normally painted, such as a lamp post on PME, nor would I worry if the ground path is poor, as it is indoors on a wooden floor, or even for an occasionally used storage container used by booted workmen on a thick layer of free-draining gravel. I would worry about the same container in frequent use in a farm yard sitting in lots of mud and conductive animal residue, or where children in bare feet, or expensive livestock, may get near it.

The regs require us to worry about metal cars on EV chargers outdoors, and caravans. In other cases, like this, you need to decide how much of a risk this is. For comparison, the static vans round here, (mother in law has one) are all installed as TT, as they have little flower beds beside  and are entered  via metal steps that are concreted to the true ground, so the credible risk is simultaneous contact with the hand rail of the steps and the front door, and I'd tend to suggest what you have in mind may be similar.

In terms of the regs, maybe not, as static caravans are not explicitly mentioned. But you should ask is the risk the same - the problem with a PME system generally, and this is true for car chargers garden sheds and containers / portakabins, and barns in farm yards, that the PME ' earth'  is not quite at the same potential as the true terra- firma earth, and this can lead to discomfort tingles if the user has simultaneous good contact to bare earth, or something at bare earth potential, and something at the PME earth potential . Also under network fault conditions, the PME 'earth' can be at a significant fraction of the phase voltage, but indoors in the dry, who cares, as it is all bonded, and goes to the same high voltage, and no shock is felt.


So we should ask is this a problem for this case - can someone touch the PME earth on the caravan door frame perhaps, while also touching the true ground with their feet ?

Professionally, I'd not worry about things that are seldom touched and normally painted, such as a lamp post on PME, nor would I worry if the ground path is poor, as it is indoors on a wooden floor, or even for an occasionally used storage container used by booted workmen on a thick layer of free-draining gravel. I would worry about the same container in frequent use in a farm yard sitting in lots of mud and conductive animal residue, or where children in bare feet, or expensive livestock, may get near it.

The regs require us to worry about metal cars on EV chargers outdoors, and caravans. In other cases, like this, you need to decide how much of a risk this is. For comparison, the static vans round here, (mother in law has one) are all installed as TT, as they have little flower beds beside  and are entered  via metal steps that are concreted to the true ground, so the credible risk is simultaneous contact with the hand rail of the steps and the front door, and I'd tend to suggest what you have in mind may be similar.