Generator Installations and EIC issue

[Electrifying]

The word 'competence' again springs to mind.

If the OP has to ask the questions that he has.....on what is essentially a DIY forum - should he be installing back up generators.

I'm no expert on generator installation, but even I know the basics.

Generators come with three types of earthing 'arrangements' - dependant on their use.

As far as I can remember - without looking it up -

You can have a small portable generator with no earthing - bit like a class 2 - this would normally feed one or two items of portable equipment.

You can have a CPC connected to the neutral (at the generator) and run along with the 'Line' and 'Neutral' conductors........basically a TN-S......which sounds a bit like the OPs set up - but I think this earth is kept totally seperate from any other supply earthing arrangements (i.e. DNO).

And finally, you can have a similar setup to option 2 above, but with the neutral (at the generator) referenced to earth, via an earth electrode (a rod).......again, I think seperate from any other supply earthing.

I think the advice is to combine earthing if there are two supplies (e.g. two generators) operating equipment in close proximity.

You have to look at it as a seperate supply install and treat it that way.

I don't think I'm far out on what I've described - like I said, I'm no expert - but I think an electrician tasked to install two generators should have a grasp of these principals and not be asking on a DIY forum........quite scary, really.

 

[JohnW2]

The word 'competence' again springs to mind. If the OP has to ask the questions that he has.....on what is essentially a DIY forum - should he be installing back up generators. I'm no expert on generator installation, but even I know the basics.

Indeed - that's exactly the point I have been making.

Kind Regards, John.

 

[JohnW2]

....You can have a CPC connected to the neutral (at the generator) and run along with the 'Line' and 'Neutral' conductors........basically a TN-S......which sounds a bit like the OPs set up - but this earth is kept totally seperate from any other supply earthing arrangements (i.e. DNO).

It's obviously not quite like TN-S since (except 'by accident' - see below), if you somehow managed to totally separate this from the 'other supply earthing arrangements' (or if, say, the supply PNE was lost and there were no bonded ecps), there would be absolutely no 'T' in the equation at all - in fact, you'd just have a floating supply and installation.

In reality, 'kept totally separate from any other supply arrangements' is nearly always going to be impossible, because of bonding and parallel paths.

My small standby generator mainly supplies a dedicated 'generator lighting circuit' which really is totally separate from the rest of the house's installation. However, it can also supply the central heating electrics ('plugged in', when required, therefore totally isolated when not in use) - and once it's doing that, there are inevitably paths between the CPCs of the generator circuit's and those of the house's main installation.

Kind Regards, John.

 

[SgtTrojan]

Christ. As you correctly identified this isn't an IET Platinum Membership forum so please don't act like you are the presidents of one.

The OP, as you keep referring to, still hasn't received the response to the OP's questions. Get with the real word and provide help when asked rather than acting like some jumped up fleshend response from someone who thinks and expects it all to fall in line with British Standards 100% of the time. If you can't respond to the help then stub your lip and let the thread develop into a conclusion.

YES. We know how it should be done. BUT IT HASN'T
YES. Your knowledge was asked of. BUT YOU JUST SLAP YOUR FLESHEND ON THE LEATHER TABLE
NO. The OP didn't expect to have posters knowledge rammed down the hole in his c*ck but it was.

Thanks to everyone that helped. Thanks to everyone that led to this point but to question your knowledge you still haven't answered the questions.

 

[SgtTrojan]

Kind Regards

Yeah right.

 

[Electrifying]

OK, Trojan, as best as I can........but like I said, I'm no generator expert.

My BLUE

Hi Chaps,

I have a few grey areas in my brain regarding the completion of the EIC for two generators we have just installed. Generators 1 and 2 installed to individual changeover panels in a building. Totally separate installations.

1) Supply characteristics:

a) Earthing arrangement - single core connected to MET of installation so TN-S? Should the generator have it's own earthing too?

The generator doesn't need 'earthing' - you are providing an earth path back to the generator to be used by the installation.
I thought it had to be a seperate earth from the supplied (DNO) - but maybe it doesn't.
The earth from the generator is connected to the MET because this is where all of the installation's CPCs / Bonding etc should be connected to......it's not to 'earth' the generator - it's to give the installation a path back to the generator.

b) PFC and Ze. It's a back up generator but considered the source of supply so how do you get around this? It can't run just to test at the changeover panel.

Surely you can isolate the main supply and run the generator - then you do the necessary 'live' tests for the generator 'supply'.

2) Particulars of the installation

a) Means of earthing - Distributors facility as the generator is earthed via the MET?

No. The generator isn't earthed. The generator is providing an earth to the installation.
Your 'single core' earth will run back to the generator and be connected to the neutral at source. This point of connection could also then be connected to a local earth electrode, if required.

You need to treat it as two supply - one supply has the DNO provided earth.......the other has the earth provided from the generator.

b) Main protective conductors - None seem to apply

These should be in place anyway (for the existing installation/supply.)

Bonding of 'extraneous conductive parts' wouldn't actually be required whilst the generator supply was running - UNLESS you 'rod' the generator at source, then they would be required, as normal.........but as they will already be in place for the main supply, it doesn't matter.

The only additional earth will be the earthing of the generator frame/metalwork if required, to the combined neutral/earth point at the generator.

3) Schedule of inspections
This should only relate to the generator feeds right?

In theory.
But I think it would be required that you inspect/test the installation to the point that you can guarantee it's safety when the generator kicks in.

4) Schedule of Test Results

The DB information at the top is not applicable. Circuit details will all relate to the single core AWA we installed. One row per singe core.

I can only give a similar answer to what I said for the Schedule of Inspections.

You will have seperate schedules for the additional supply - I think there's a box that you tick on an EIC, and then you provide the additional schedules.

I think what you need to do is complete an EIC for the generator installation and switchgear etc.
This EIC would then be accompanied by two sets of 'Schedules' - one for the DNO supply and one for the generator supply........because the test results for each are going to be different.

Thanks in advance.

Hope that's helpfull in some way - apologies if I am slightly out on my info, but I don't do a lot of back-up supplies.......anyone with a bit more hands-on, please feel free to correct me.

 

[Electrifying]

Sorry, double posted it

 

[SgtTrojan]

Wonderful. Thank you for your reply dude. I hope your responses don't get ripped to pieces but rather discussed in a manner which demands respect.

 

[ban-all-sheds]

The OP, as you keep referring to, still hasn't received the response to the OP's questions. Get with the real word and provide help when asked rather than acting like some jumped up fleshend response from someone who thinks and expects it all to fall in line with British Standards 100% of the time.

No - YOU get with the real world you nasty little incompetent fool who is getting bent out of shape because he hasn't got the answers he thinks he should be able to dictate.

YES. We know how it should be done. BUT IT HASN'T

The that's it. End of.

Walk away.

Have someone who knows what they are doing tackle it.

YES. Your knowledge was asked of. BUT YOU JUST SLAP YOUR FLESHEND ON THE LEATHER TABLE
NO. The OP didn't expect to have posters knowledge rammed down the hole in his c*ck but it was.

No - you expected people here to rescue you from the hole you're in because you're working outwith your competence.

Go away.

 

[SgtTrojan]

Oh come on sheds. I use this site as a knowledge bank not to be ridiculed for something I clearly know nothing about. Granted, after a few pints last night the replies above narked me a bit but before it got out of hand the intention was to bring the focus back to the solutions rather than in "incompetence".

I've stuck up for you big time on here when you were at the fat end of your bluntness dude. :s

 

[holmslaw]

What were you actually contracted to do?

 

[SgtTrojan]

Based upon a design (third party for the client) we secured the contract to install what was in the spec and on the drawings. The drawings included the cable requirements, no mention of generator earthing. Due to my inquisitiveness, when planning ahead for the EIC issue, I posted here. The installation isn't even finished yet. No cables are yet installed. I am not in a hole so to speak. But could be if I ignore the issue and one day "gripping the rail".

 

[Electrifying]

Trojan, any chance of posting the make and model of the generators - I wouldn't mind having a look at the specs etc. - only out of curiosity.

Give us the model of the change-overs you're installing as well........I wouldn't mind understanding this a bit more myself.

 

[holmslaw]

..

 

[bernardgreen]

My BLUE
These should be in place anyway (for the existing installation/supply.)

Bonding of 'extraneous conductive parts' wouldn't actually be required whilst the generator supply was running - UNLESS you 'rod' the generator at source, then they would be required, as normal.........but as they will already be in place for the main supply, it doesn't matter.

The only additional earth will be the earthing of the generator frame/metalwork if required, to the combined neutral/earth point at the generator.

Looking back at how standby generators were installed at hill top radio sites Electrifying has got it right. Generators were star wound with the star point providing neutral and this was both earthed by a rod and connected the main station earth. Some sites had incoming 3 phase supplies at 11Kv The star point of the 11kv 440 transformer was earthed. A few small sites had single phase and neutral incomers at 230 volt and in all cases the neutral was earthed at the site.


There were systems in place at some sites to detect high currents from incoming neutral to earth and if these occured the incommer was considered faulty and the generator bought up to speed and then the incommer disconnected the generator took on the load.

The reasoning was that high currents from incoming neutral to earth indicated a developing fault on the network which could reduce the 230 volts and affect operation of equipment