Generator Earthing/Voltage etc

[Nightmare1308]

Evening all,

Got a 5.75kva Generator on site powering a show home via a 32A commando plug.
I have 110 L-E 110 N-E and 222v L-N.
I have an Earth electrode in the ground feeding the E point on the gernator with a 10mm bond from the consumer unit to the same E point.

The problem i have is i cannot get a Earth path for my RCBO’s installed to test them to check the house is safe whilst on the generator.

I have a feeling i need to put a N-E link within the generator (1 side of the Tap to the earth point) before its inbuilt RCD.

Does any one have experience in this to one if it’s safe for me to do?

I have already spoken to the manufacturer but they were unhelpful and told me it should work straight out the box.

I’m just concerned if my test kit cannot see an Earth and N-E has voltage it’s unsafe as we know, no earth means the RCBO’s won’t work.
N-E is also live no matter what atm as i only have single pole McB leaving it with a potential even when the McB is open.

Hope you can help.

 

[buzzlightyear]

did some body post ask about a gen the other day. you will find it !

 

[buzzlightyear]

Portacabin/generator earthing - https://www.electriciansforums.co.uk/posts/1329595/

 

[Nightmare1308]

Portacabin/generator earthing - https://www.electriciansforums.co.uk/posts/1329595/

Appreciate that, thought i would have to link it myself but didn’t want to cause any damage, i take it i link the one cable of the pole that doesn’t go to the MCB.

thanks again

 

[Lucien Nunes]

I would check that the centre point of the winding is not earthed first. It could be that the 110V either side of earth is just chance due to equal leakage from both lives, but it could be an internal connection in the generator that would be correct for a USA / Far East version. In that case, earthing one end would cause a short-circuit across half the winding, and the centre-tap-to-earth link would have to be removed first.

 

[Nightmare1308]

Yes i discovered that today and i put the N-E link in and it started to smoke from the alternator so i switched it off.
I agree it’s center tapped.

A way round this could i leave the Earth out of the Plug from the generator and Install an Earth steak for the house Earth.

would this be a safe way to do it if it works, or would that create a potential on the chassis of the generator in a fault condition? If so this should be covered by the generators RCD?

Is there any books i could buy to educate myself for future, so i am ready if i do a generator again?

Thanks for your reply

 

[Deleted member 26818]

Are your RCBOs designed to work with 110V, or 230V?

 

[Lucien Nunes]

would this be a safe way to do it if it works?

No! That will make the generator chassis live at 110V to earth all the time, even when there's no other fault. The only way to make this unit usable in a TN system is to remove the CT-E link.

 

[Nightmare1308]

Ok where do i find that on a generator as the board shows no links, unless i take all the parts of the generator off ?
Even if the generator is steak to Earth, i would of thought it would elemiate that issue?
i was trying to create a TT for the house until power is on site, like how you would if you submain a cable to a garage and not connect the armourings at the garage end. Thought this would be the same method if that makes sense?

RCBO are standard house ones so 230v

 

[Deleted member 26818]

To remove the centre tap, you would have to dismantle the alternator.
I believe your 230V RCBOs will not work with the generator as it is at present.
Check the generator RCD, I suspect it is rated for 110V.

 

[Ian1981]

ALL this talk of dismantling generators and installing links shouldn’t even be mentioned.
If it’s the wrong type of generator then get a suitable working replacement for your needs.

 

[Deleted member 26818]

Absolutely no reason why it can’t be mentioned.