RCD on generator incomer

[Dave-sparks]

That doesn't sound right!

Neutral is usually connected to earth, that's what makes it neutral rather than just another live.

Generally the connection is made at the source of the supply, so at the substation for an normal domestic supply.
And when the local nomadic travellers come around and remove that bit of copper going in to the ground it causes a lot of damage and people's appliances start going pop!

 

[Ubique]

I would almost always expect an RCD on a generator supply as generators are rarely able to deliver enough current to operate the usual fault protection.

The exception being generators set up without an earth reference to provide an isolated supply where an RCD is obviously pointless.

We have different backgrounds then. Unless the generator output is a final circuit, then it should have overload (and back EMF) protection, RCD's are generally to protect final circuits. The one above has two RCD's with no method of discrimination, leading to nuisance tripping. My experience of generator installation and specifications comes from prime sets, up to 3MW per installation. I appreciate that is wildly different to a portable standby set with a changeover switch but an RCD at the point on the changeover switch is to me, the wrong protection in the wrong place.

 

[dobbslc]

No it's right, all of our hired-in gennys have stickers on them noting that they are the same.

Yes it's the same on all the sets we use but that's before any earth leakage device/sensor, it sounds like the earth/neutral is connected after the RCD in the extension lead here? Maybe I've read it wrong.

 

[dobbslc]

Something sounds a bit odd here, your earth reference should connect back to a single point. Having multiple points connected to seperate earth references may lead to odd circulating currents.

Sounds like @addjunkie is in an overhead TT supply so this could be a good point.

 

[addjunkie]

Yes it's the same on all the sets we use but that's before any earth leakage device/sensor, it sounds like the earth/neutral is connected after the RCD in the extension lead here? Maybe I've read it wrong.

Ill check this one day when its mot keeping the heating on, but from memory the earth and neutral are connected at the generator end of the lead from the generator to the changeover switch, therefore before the RCD.

 

[addjunkie]

Sounds like @addjunkie is in an overhead TT supply so this could be a good point.

The house is earthed by a cable incoming with the other two conductors from the pole.

only earth stake now connected is at the generator side of the changeover switch

 

[dobbslc]

Ill check this one day when its mot keeping the heating on, but from memory the earth and neutral are connected at the generator end of the lead from the generator to the changeover switch, therefore before the RCD.

Ok maybe I've had a really hard week so far (I have had a really hard week so far ) but can you tell me where the tripping RCD is? I'm confused! Is it in the generator or the changeover unit or somewhere in between?


Photos we need photos.

 

[sparkysy]

If the incoming supply is TN-S or TNCS then I would not be relying on the incoming earth under power outage situations, just in case the cable has been compromised and in fact there is no earth connection at all! I would be putting my own earth in for the generation supply.

I would also want to see some pictures of the current set up and incoming supply cut out before making comment on the rcd situation as it is not entirely clear!
Sy

 

[MCKDAVID]

We have different backgrounds then. Unless the generator output is a final circuit, then it should have overload (and back EMF) protection, RCD's are generally to protect final circuits. The one above has two RCD's with no method of discrimination, leading to nuisance tripping. My experience of generator installation and specifications comes from prime sets, up to 3MW per installation. I appreciate that is wildly different to a portable standby set with a changeover switch but an RCD at the point on the changeover switch is to me, the wrong protection in the wrong place.

3MW is that all, starter motor for the kit @addjunkie is used to then......

 

[Ubique]

If the incoming supply is TN-S or TNCS then I would not be relying on the incoming earth under power outage situations, just in case the cable has been compromised and in fact there is no earth connection at all! I would be putting my own earth in for the generation supply.

I would also want to see some pictures of the current set up and incoming supply cut out before making comment on the rcd situation as it is not entirely clear!
Sy

That's a good point - if there is a local earth spike, it needs to be tested too.

 

[Ubique]

Also you need to make sure that your local earthing arrangements don't become the earthing arrangements for the whole leg of the distribution network you're on.

 

[jimbo84]

Some generators aren't suitable for this application due to their internal wiring. Could that be the problem? They render all RCDs within the existing installation useless which may be why the ones in the house aren't tripping.

In my limited experience with generators, for this use you'd have a Neutral to earth linked genny, referenced to earth with an RCD for fault protection on the genny. The CU/DB inside the building would then provide protection for the individual circuits.

 

[addjunkie]

3MW is that all, starter motor for the kit @addjunkie is used to then......

In a past life I had 100mw ish to play with, but that was back in the day when I had people who knew far far more than me in my team. Now Im stumped by 5.8 kva.

So tonight I switched off one circuit in the house that seemed to be a source of irritation,all seemed a bit more stable, but simple changes and it tripped again. Big load changes like switching the tv on andthe RCD went. Then after about an hour of stable supply it stopped. Thought it had tripped, but wouldn't reset. Upshot after some investigation in the dark it appears there is no ziggies coming out of the socket, no loose connections, head scratch suck through the teeth, couldnt find the instruction book. Mrs came to find me thinking where is he, its dark and raining.

She noticed a light on in the holiday cottage. Ahhhhhhh relief mains back on.

So tomorrow I shall open up the change over switch and confirm how its connected. With pictures. Then hopefully find out why there are no ziggies coming from the generator.

In the mean time thank you for your on going assistance.

 

[addjunkie]

So generator is fixed, crimped terminal had snapped due to vibration I suspect.

Now this is the change over switch inside and out. And it appears to me that the earth spike connects to the house earth inside the changeover switch. As the house earth comes in from the poles, I dont think this is correct, as suggested earlier. Other than that the RCD is on generator inlet, both live and neutral are switched.

 

[Matrixx]

All the earths should be connected together, you only get problems with circulating currents when you are in parallel with the grid or dual supplies, this system is break before make so no paralleling occurs.

I don't think the RCCB is necessary, it should be in the house consumer unit if anywhere . 30mA is very low normally for human protection. you need to remember that the generator manufacture does not necessary know where the generator is going to be used, it end up feeding an extension lead into a field for camping so then it would be the main protection.

Most rental generators 25-3000kVA have a bypass switch for earth fault protection as they are notorious for nuisance tripping.

I would not think there is anything wrong with the electrical side of your house, just a sensitive protection device in the wrong location in this case.

The last big project I worked on had six 600mW steam turbine generators ( 3.6gW)

 

[addjunkie]

All the earths should be connected together, you only get problems with circulating currents when you are in parallel with the grid or dual supplies, this system is break before make so no paralleling occurs.

I don't think the RCCB is necessary, it should be in the house consumer unit if anywhere . 30mA is very low normally for human protection. you need to remember that the generator manufacture does not necessary know where the generator is going to be used, it end up feeding an extension lead into a field for camping so then it would be the main protection.

Most rental generators 25-3000kVA have a bypass switch for earth fault protection as they are notorious for nuisance tripping.

I would not think there is anything wrong with the electrical side of your house, just a sensitive protection device in the wrong location in this case.

The last big project I worked on had six 600mW steam turbine generators ( 3.6gW)

So hypothetically if I bypassed the changeover RCCB, would then the ones in the house board not just trip, there are the same rating?

 

[awemawson]

In a past life I had 100mw ish to play with, but that was back in the day when I had people who knew far far more than me in my team. Now Im stumped by 5.8 kva.

100 milliwatts isn't going to do much

(I think your decimal place has slipped a bit!)

 

[brightspark]

So hypothetically if I bypassed the changeover RCCB, would then the ones in the house board not just trip, there are the same rating?

if the mains supply to the db in the house is rcd protected the one in the generator is only protecting the piece of cable from the changeover switch to the alternator and not needed

 

[Ubique]

if the mains supply to the db in the house is rcd protected the one in the generator is only protecting the piece of cable from the changeover switch to the alternator and not needed

To do that, it'd have to be mounted on the generator. - but yes, it is superfluous.