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#146270 - 11/22/06 09:37 AM Portable Generators  
Kenbo  Offline
Joined: Apr 2006
Posts: 233
Quick question

If you use a portable generator should you use it with an RCD, or is it pointless as the generating set is isolated from earth?

Thinking of the small ones popular with caravans and small works.

der Gro├čvater

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#146271 - 11/22/06 10:36 AM Re: Portable Generators  
32VAC  Offline
Joined: Jun 2004
Posts: 202
Alice Springs, NT, Australia
In regards to the earthing, depends if the unit has been fitted with a MEN link. Which country are you in?

#146272 - 11/22/06 02:59 PM Re: Portable Generators  
Wolfgang  Offline
Joined: Sep 2005
Posts: 153
the very West of Germany
Kenbo being from Scotland, I'd suppose that the small units work as IT-systems. This means they are probaby isolated. RCD won't function in this case and is not necessary. Often there is even no metal in the place of the earth pin (or brackets on the continent).

#146273 - 11/22/06 04:55 PM Re: Portable Generators  
Kenbo  Offline
Joined: Apr 2006
Posts: 233
32VAC sorry forgot the interantional scope of this forum. As Wolfgang says I am in Scotland so working with the UK system. (MEN link is that an earth-neutral link?)

Wolfgang, that is my thinking also but I do not know for shure I will have to go and look at one now.

I was just reading my issue of "Wiring Matters" and there is an artical about small generators and this para got me wondering
A small single phase generator is often run as a floating system. A means of earthing is not required. In such a system the generator is deliberately not connected to external metallic parts nor is one pole of the single phase electrical system connected to earth.
In such a system there is no path for an earth fault current to return to the 'seperated' winding of the generator. Safety must be ensured by meeting the following conditions....."
(no mention of RCDs)

The magazine is not yet posted on the net but I will put in a link once it has been


der Gro├čvater

#146274 - 11/23/06 03:17 AM Re: Portable Generators  
32VAC  Offline
Joined: Jun 2004
Posts: 202
Alice Springs, NT, Australia
MEN is multiple earth neutral where the neutral & earth are tied together at switchboard.

A look at Australian Standard 3010:2005 chapter 4 shows two different methods of connection. The first picture is of a genset with the earth not tied to the neutral & using double pole switching of the outlets.

The other picture shows an RCD fitted to a portable genset with the lines side of the RCD connected to the earth point. The use of the RCD permits the use of single pole switching outlets.

If I can find an online copy of these pictures, I will arrange to have them put in this thread.

#146275 - 11/23/06 09:11 AM Re: Portable Generators  
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
If the generator output is truly floating, then an RCD would be of little use.

The issue of a bond between one side of the generator output and its frame raises some more points though. If such a bond is in place, then I'd definitely want the genset earthed, otherwise an accidental earth fault on the other side would raise the genset frame and everything else connected to it to 240V.

#146276 - 01/25/07 02:00 PM Re: Portable Generators  
lyledunn  Offline
Joined: Jun 2002
Posts: 159
It is generally accepted that such arrangements are confined to a single circuit supplying a single class 2 tool. Thus the possibility of a double fault is very much reduced.


lyle dunn

#146277 - 01/27/07 07:00 AM Re: Portable Generators  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,223
SI,New Zealand
I know the diagrams you are talking about.
I just can't rip them from a PDF file I have here on my computer.
Can anyone else help?.
Send me an e-mail if you want the file.

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