So reading the latest regs I take it we are to provide an earth rod in a prosumer setup for island mode supplies.
Any ideas how this works practically in a top floor flat?
True, but only while it is a self contained box, and a shock or fault to something truly earthed is impossible. As soon as that mobile unit parks, and an extension lead is thrown out the back for a floodlight or something, then it gets sticky, what happens if that extension lead lands in a puddle or snags on barbed wire so that the brown core is now earthed to terra-firma ?
You can be the first to grab hold of the vehicle door handle in that case if you like...
Similar situation to using ADS out of doors and grabbing hold of a damaged flex while standing on the ground - we primarily rely on double/reinforced insulation (i.e. sheathed flex) to make the occurrence less likely, and then on additional protection (30mA RCD) - in the mobile unit scenario the current would be returning via the brown core as it were, but the RCD should see the imbalance just the same.
So when we park up, you are supposed to drive a spike or park with a contact plate under one of the tyres squished into something moist like grass verge.
Might well be 'a good thing', but not a regs requirement in all situations as far as I can see.
I might even point to Fig A722 for another example of "unearthed" TN system (IN-S perhaps?) - complete with RCD for ADS on the secondary side (if misdescribed as a separated system).
- Andy.
Similar situation to using ADS out of doors and grabbing hold of a damaged flex while standing on the ground - we primarily rely on double/reinforced insulation (i.e. sheathed flex) to make the occurrence less likely, and then on additional protection (30mA RCD) - in the mobile unit scenario the current would be returning via the brown core as it were, but the RCD should see the imbalance just the same.
In one important aspect it differs -
The RCD trips the moment the extension lead goes in the puddle or snags on the wire fence with the equipment in the garden case, so disconnection times are not always a safety of life thing, while with the unearthed vehicle, the RCD only starts to trip when someone grabs hold of it with one foot on the floor, and enough current passes through them to fire the RCD, the chassis may be live for days before that occurs - the 'Automatic' part of the ADS is much weaker.
In someways it is more like a live class one device with a broken CPC - and that would not normally be considered safe.
A stand alone vehicle or trailer with generator and all the electrical loads inside is not an issue.
Mike.
Similar situation to using ADS out of doors and grabbing hold of a damaged flex while standing on the ground - we primarily rely on double/reinforced insulation (i.e. sheathed flex) to make the occurrence less likely, and then on additional protection (30mA RCD) - in the mobile unit scenario the current would be returning via the brown core as it were, but the RCD should see the imbalance just the same.
In one important aspect it differs -
The RCD trips the moment the extension lead goes in the puddle or snags on the wire fence with the equipment in the garden case, so disconnection times are not always a safety of life thing, while with the unearthed vehicle, the RCD only starts to trip when someone grabs hold of it with one foot on the floor, and enough current passes through them to fire the RCD, the chassis may be live for days before that occurs - the 'Automatic' part of the ADS is much weaker.
In someways it is more like a live class one device with a broken CPC - and that would not normally be considered safe.
A stand alone vehicle or trailer with generator and all the electrical loads inside is not an issue.
Mike.
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