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?
My current install is a house and so it’s fine to use a rod as an electrode (though I always worry I’m going to hit a stray drainage pipe). I just wanted to query the flat situation and wondered whether an electronic solution had been considered? Rather than the passive electrode.
I ask as Ive seen lots of TNCS EV installs without an electrode or PEN protection and feel this is bound to happen at the cheaper end of installs with ‘island’ modes.
Although after thinking about it, is the objective to provide an uninterrupted reliable earth electrode for island mode, rather than reliance on the DNO main earth which has a greater risk of being disconnected during this “Grid failure” time.
After all no point in a backup island mode and all the reconfiguration required if it just fails during grid failure!
That third floor flat I gave as an example that has its intake on the ground floor has an earth conductor from the flat to ground level, it does not need to be disconnected from the DNO earth, so it should be possible to use it to connect to a rod, but I would not particularly want to be the person actually trying to put a rod in.
Regards the IET Code of Practice for Electrical Energy Storage Systems I am going to have to have a discussion with the IET sales team, I had a copy from the IET stand at Elex in Coventry last week and there was a debate about if the card payment had gone through, so they took my contact details just in case, at the moment it does indeed seem that I have the book but have not paid for it!
I just wanted to query the flat situation and wondered whether an electronic solution had been considered?
Some products available on the market at the moment offer "floating" output option.
BUT
The IET Code of Practice does not recommend this is used in domestic installations, and provides the reasoning for it. The MCS standard for battery storage aligns with that line of thinking.
Oh dear, you (or rather your bank details) might be sent to Coventry.
I need an earth to provide ADS.
Not necessarily - in a TN system the actual ADS part will work perfectly well with just the c.p.c.s connected to the supply star point (N) - the connection with Earth merely gives the system a 0V reference (which has a number of other safety and practical benefits) . In some situations - e.g. self contained generators aboard mobile units - the regs specifically say that a connection to something like the vehicle chassis may be used instead of an actual Earth electrode, despite it being pretty well insulated from the ground by rubber tyres.
- Andy.
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...
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.
Mike
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.
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site
