4 Core SWA linking two legs of a ring circuit

[Chris Packet]

Hmmm good points about the bill being split and I'll have a look at the volt drop again. The main argument I keep hearing for an earth spike is that the loop readings will probably be too high without one and why wouldn't you put one in?

It's only a quote at the end of the day but one that could easily spiral into a right cluster hence why I thought I'd get some opinions!

 

[VoltzElectrical]

Hmmm good points about the bill being split and I'll have a look at the volt drop again. The main argument I keep hearing for an earth spike is that the loop readings will probably be too high without one and why wouldn't you put one in?

It's only a quote at the end of the day but one that could easily spiral into a right cluster hence why I thought I'd get some opinions!

Unless you are already on a TT system, an earth spike won't bring the readings down, and given my previous point, is the least of the concerns regarding the viability of this installation.

Note that I don't use 'your concerns' as what you have been asked to do has been very poorly thought through by the customer.

 

[Engineer54]

Just think about someone using a JetWash outside his garage, many of which are over 2 KW, and even most vacuum cleaners run at around 1.6 to over 2KW as well.... Then think about the guy that just uses his garage to park his car in, maybe uses the light now and again, he'll be paying a portion for all his neighbours annual car cleaning costs etc!! lol!!

 

[HandySparks]

The occasional-use appliances aren't such a big deal.

However, someone leaving a heater on over the winter to keep his car (or workshop) warm could get mighty expensive.

 

[davesparks]

Hmmm good points about the bill being split and I'll have a look at the volt drop again. The main argument I keep hearing for an earth spike is that the loop readings will probably be too high without one and why wouldn't you put one in?

It's only a quote at the end of the day but one that could easily spiral into a right cluster hence why I thought I'd get some opinions!

That's a pretty big earth nest you 're planning to install if it's going to have a low enough Ra to lower your loop impedances!

You wouldn't put one in because on a TNS supply it will have no effect unless you install multiple long rods well spaced apart. (Earth nest) and get a reliable and very low (below 1ohm) Ra.

If your Calculated Zs is too high then a bigger cpc will do more good than adding an earth rod.

 

[Engineer54]

The occasional-use appliances aren't such a big deal.

However, someone leaving a heater on over the winter to keep his car (or workshop) warm could get mighty expensive.

It is, when you are talking about/in annual costs!!

They will all soon know who's leaving a heater on over winter, it'll be the only garage where there isn't any snow sitting on the roof!! lol!!

 

[Octopus]

All in all its a pretty stupid idea!

 

[Chris Packet]

That's a pretty big earth nest you 're planning to install if it's going to have a low enough Ra to lower your loop impedances!

You wouldn't put one in because on a TNS supply it will have no effect unless you install multiple long rods well spaced apart. (Earth nest) and get a reliable and very low (below 1ohm) Ra.

If your Calculated Zs is too high then a bigger cpc will do more good than adding an earth rod.

Well that's an interesting point, would it also make no difference on a TNCS system? (Gaps in my earthing system knowledge showing here...) Although with an rcd protecting the circuit the max Zs could be up to 1667 ohms and still comply in theory. Not that anyone would find that acceptable!

 

[amckay]

Maybe an afterthought, but you said a row of 6 garages with another row of six about 11meters opposite? Has the client requested external lighting to illuminate the "yard"? Maybe a few extra quid in it there too for a pint!

 

[VoltzElectrical]

Maybe an afterthought, but you said a row of 6 garages with another row of six about 11meters opposite? Has the client requested external lighting to illuminate the "yard"? Maybe a few extra quid in it there too for a pint!

Did you just completely IGNORE all of the much more important points regarding the viability of the proposed installation, and if so, why?

 

[Lucien Nunes]

Quite apart from the billing issues, one circuit for all the separate occupiers? What happens if one tenant has a dehumidifer which occasionally trips the RCD when its water tank leaks, or the OCP trips when seven heaters happen to come on at once on their thermostats? How is the landlord going to trace / identify the problem? Doesn't meet basic design requirements by my book.

 

[VoltzElectrical]

Quite apart from the billing issues, one circuit for all the separate occupiers? What happens if one tenant has a dehumidifer which occasionally trips the RCD when its water tank leaks, or the OCP trips when seven heaters happen to come on at once on their thermostats? How is the landlord going to trace / identify the problem? Doesn't meet basic design requirements by my book.

Totally agree, well put.

 

[VoltzElectrical]

DNO supply to external street lighting type pillar, then radial to each garage each with it's own meter.

 

[Octopus]

Or what happens when one tennent decides to grow "things" in his garage!

 

[VoltzElectrical]

Or what happens when one tennent decides to grow "things" in his garage!

Not a problem if they are the only ones paying for all those UV lights, heaters, ventilation units.

Hang on, how come I know so much about it!

 

[ipf]

Or what happens when one tennent decides to grow "things" in his garage!

Pinocchio.....plenty tall tales around.

 

[amckay]

Maybe an afterthought, but you said a row of 6 garages with another row of six about 11meters opposite? Has the client requested external lighting to illuminate the "yard"? Maybe a few extra quid in it there too for a pint!

Did you just completely IGNORE all of the much more important points regarding the viability of the proposed installation, and if so, why?

Yes, I'm having problems with the forums phone app.
But I can now see Chris' post re, clients requests.

 

[urbanmonkey]

I'm not usually one to jump in with the rest of you keyboard warriors and jump on people but in this case if the OP by his own admission doesn't have much knowledge of Earthing systems (basics) then perhaps this job may not be suitable for him. No offence, but if I didn't know that putting in an Earth spike won't do anything to TN-S/TN-C-S Ze values then I wouldn't be attempting a can of worms like this one.

Personally I wouldn't touch it, far too many problems when joe public cotton on to the fact they aren't solely responsible for the bill... 11 tumble driers anyone?

 

[VoltzElectrical]

Earthing is the least of the problems of this proposed installation, but point taken.

 

[Chris Packet]

Yep a lot of fair comments about this job and I'm still learning but earthing at outbuildings seems to be one of the most disputed topics among sparks. I've seen a lot of earth spikes on outbuildings on TN earth systems and I've been told on more than one occasion if in doubt, put a spike in.

Extraneous conductive parts seems to be the deciding factor in whether to TT an outbuilding am I right?