Generator N/E link

[ban-all-sheds]

OK - imagine a generator supplying a few circuits in a house via a C/O switch.

Physical connection would be a cable from the generator to a 60309 inlet at the house end.

Q - where best to have the N/E link?

At the generator end of the cable (as shown)?

At the house end of the cable?

In the house inlet itself?

If it makes no odds I'd prefer the last one, as it keeps the cable a general purpose 60309 extension, but if there are reasons for putting the link in one end or the other of the cable of course I'll do it.

 

[1john]

Now dont quote me but if my memory serves me correct then N-E lik needs to be at the origin, being the generator.

 

[Spark123]

When I asked generac (who made my laal genny) they told me to make up a lead and do the N-E link in the plug. Also to place a label on the lead stating that it had a N-E link in it and for the generator use only.

 

[holmslaw]

..

 

[ericmark]

The Earth / Neutral link is done in the generator. Main reason is not all generators link the earth to neutral some link it to a 55 volt tapping on the output winding and if you then install a second link you have a direct short 55 volts to earth.

 

[ban-all-sheds]

Makes no difference, but doing it external to the generator allows the possibility of installing an REF relay for complete protection.

Can't see me doing that for a few-kW portable generator.

The Earth / Neutral link is done in the generator. Main reason is not all generators link the earth to neutral some link it to a 55 volt tapping on the output winding and if you then install a second link you have a direct short 55 volts to earth.

I was assuming a generator with nothing linked to earth.

 

[matt1e]

at the generator I would say as that makes it a TN-S suppy
anywhere else means you have a PEN conductor which makes it a TN-C supply

 

[ericmark]

I would agree that where the earth and neutral are not bonded then the point used to bond does not really matter.
However although I know you would not make a mistake that does not mean the next guy will not make a mistake and from mistakes in the past which we are supposed to learn from I would now always bond in the generator.

Honda was the one that caught me out. And one would have thought Honda would have complied with all the rules. It is normally only a problem where the generator is multi-voltage.

I can see the problem. How does one move the earth from centre tapped with a 110 volt supply to connected to neutral with 230 volt supply and comply with the rules on switching earths?

However with Honda's method you have an un-protected 55 volt supply and that does not comply either.

In the case I had the generator was converted to 110 volt only. However so easy to miss. And most generators I have installed the neutral to earth bond was done by manufacturer in the generator.

I was going to say with the large generators I worked on it was not pre connected but since at that time I was working for GEC who were the manufacture then it was connected by manufacturer. So from 750kva to 750Mw (Sizewell) I can't think of any generator where it was not bonded by manufacturer even if in the case of Honda to the wrong place.

The CAT 650kw units had a link which could be removed and I seem to remember many of the container type generators had a similar option.

The Petbow had a 12 winding stator which could be configured for many voltages and single or three phase (12kva) as a result with that one it was up to the guy configuring to decide where to connect the earth. I found the whole idea of zig zag wiring to get single phase from a three phase machine interesting to say the least. Don't want to connect them up after a skin full!

 

[ericmark]

at the generator I would say as that makes it a TN-S suppy
anywhere else means you have a PEN conductor which makes it a TN-C supply

I see your point but as the supplier not sure if that is a problem? Much would depend on who had access to what.

The biggest problem I see is all too easy to rely on the DNO earth which in a power cut may not exist.

However it is BAS who is doing the job so can't see that as an issue.

But in case others read this then maybe we should point out the guy doing this job is known by us and we as a result are not worried about his general understanding.

When is an earth electrode not an earth electrode? Answer when it is an extraneous-conductive-part! But BAS knows all this so no need to tell him.

 

[matt1e]

And most generators I have installed the neutral to earth bond was done by manufacturer in the generator.

I was going to say with the large generators I worked on it was not pre connected

A lot of the larger ones aren't AFAIK, they leave it to the installer to decide on the earthing system
to be honest I thought this thread was going to be about a larger one I'm nearlly always working in an industial/commercial setting these days, and yes I agree, he knows what he,s doing

at the generator I would say as that makes it a TN-S suppy
anywhere else means you have a PEN conductor which makes it a TN-C supply

just had another read and i'm wrong again

At the house end of the cable?

In the house inlet itself?

connected together at these positions would make it more TN-C-S

Matt

 

[Spark123]

Still not sure on it being TN-CS, what he is trying to achieve is earthing of the system which will make it TN. The CPC and the neutral are in separate conductors from a current carrying point of view hence I'd still go with TN-S

 

[ban-all-sheds]

For it to be TN-C-S I'd have it linked and staked at the generator end but not take the earth to the house along a separate conductor, surely?

 

[1john]

I *think* that would depend on the distance from the generator to the house. I had this issue on a job where the n-e link was done outside the property near the eves and the main dropped down the house and in at ground floor ceiling level.

 

[matt1e]

For it to be TN-C-S I'd have it linked and staked at the generator end but not take the earth to the house along a separate conductor, surely?

there are five types of earthing systems
one of these (IT) you can't use in the uk
another, (TN-C) you need an exemption to use

out of the other three (TN-S, TT, and TN-C-S) then all would have the generator end staked.
though TN-C-S would also have multiple stakes along the way hence the term PME
In your drawing above BAS I would say it could almost be classed as a TN-C supply with a TN-C-S installation as its not PME so I dont know of hand if it would be acceptable as a fixed backup supply, I'm sure someone else will, but I know TN-S would

 

[Spark123]

I don't think for a minute BAS has any intention of installing the TN-CS as above, it was just to show us how he believes a TN-CS generator supply would be constructed.
The first one BAS posted is the one he is wanting to install (TN-S) and is only wanting to know where to do the link.

Not sure on you not being allowed to use IT supplies as I have come across one before in a testing area.