can someone tell me why?

[wattsup]

So, install a transfer switch single phase 100a 230v (double pole changeover) why does the maker of the switch insist on an earth spike?

All earths are connected anyhow through the switch. In reality all earths are as one, just like the incoming supply. The earth spike does nothing?
Does it?

It don't matter cost wise, but I can't get my head round the reasoning

 

[trebor]

sorry I could not find the original question but it would appear you may be talking about a generator via a c/over switcth ?

if so the earth electrode is a regs requirement BS7671 551.4.3.2.1, the reason being that if the loss of supplly is due to a network cable severance then its higly likely that the earthing source has been lost also , especially the case with pme

if it wasnt about gennys then ignore all I said!!

 

[wattsup]

Yes a gen transfer switch. neutral earth protection on utility incommer. Water, lead pipe earthed, gas earthed and normal bonding.
The lead water pipe is better than any earth spike..normally. All earths combined in effect.

Yet the earth spike will not protect the gen steel frame, nor will the combined earth combination. All the spike does is give slight protection if not pme, in effect a double earth spike, utility supply and on mains failure gen supply. I don't get the reasoning behind the rule. The pme will protect the installation, but it does nothing to protect the source feed, ie the generator, all... well, most are floating earths, by installing an earth spike will not prevent shock through the gen steel framework, unless of course a physical connection is made, which if a portable generator cannot be accomplished for normal joe bloggs usage.

 

[trebor]

Hi wattsup

I think this link may help you Which Generator advice and tips

it explains why the seperate electrode, how to configure the genny link up to use mains rcd protection when supplying via a transfer switch and ccu

basically portable generators are safe to use with the floating earth as far as the frame is concerned due to the configuration of the generator windings

trebor

 

[wattsup]

Yeah thanks for that trebor, it seems portable gensets escape the rule. A fixed set ie Auto transfer must have the framework earthed, yet portable or manual changeover do not.
Which begs the question that the iee make, 'Temp installations should be treated as fixed'
I would assume a gen backup is temp, especially the biggies 12kva and over...

I understand the n&e link (to give protection for existing cu's rcd's etc) when on gen power, but in real terms the gen frame is unprotected if using a manual changeover switch.

Some sets are basically identicle, auto start or manual changeover, all that differs are the electronics to provide autostart. So the actual windings are the same for both sets. The autostart is of course more expensive, but the auto start set framework must be earthed, the manual changeover set does not.
I can see an anomaly with iee guidence

What I'm saying is:
fault on gen output (manual changeover), trapped flex, swa,etc etc, under gen set or whatever. Fault current to earth (none protected gen frame) may not trip the set, especially a n&e fault.
I believe this is not beyond reasonable doubt considering the lengths taken to avoid 'natural shocks' from normal mains supply in all electrical installations.