RCD's and portable generators

[Simon]

This relates to the UK, EU and USA, I know standards may differ. Does a portable generator require an RCD?

[themadhippy]

any help
https://electrical.theiet.org/wiring-matters/years/2020/82-september-2020/mythbusters-6/

[Simon]

Thank you very useful, as i do have a copy of BS7671:2018, chapter 55 is all about temporary installations. Does a single generator with one connected load count as an installation?

[Jeroen3]

This is a complicated subject and the usage area defines what rules apply.

Typically in the netherlands:
Mostly, yes mandatory, even if not functional as noted in the rules. "if the generator is used a IT (no earth pin) then they will not act"
Exceptions for using generators as IT-system are the amount and class of devices attached and the length of cable. One class I or some class II, within 30m and less then 3kVA.
Above 18kg isolation monitoring is even mandatory when used on building sites.

In any case all metal structures or objects need to be bonded when the generator is to power them to not have potentials between them.

[Simon]

We supply an off the shelf inverter generator, this thing is a plastic case. I'm not even sure it has an earth bonding point on it and unless that is has and is staked into the ground an RCD will not really work anyway.

The regulations quoted in the article are from "requirements for electrical installations" or BS7671:2018, this specifically states at the start that it does not apply to machinery and a generator that is put on the ground, run for 4 hours at most and then taken away again does not sound like an installation. If the generator were in place for a longer period of time with various extensions supplying different things then it would start to class as a temporary instalation.

[themadhippy]

Does a single generator with one connected load count as an installation?

The answer should be in the big book of rules under definitions,from memory an installation is an assemble of electrical equipment

as i do have a copy of BS7671:201

whilst aimed at the entertaiment industry it maybe worth having a look at bs7909,unfortunately since the niceic/napit cartels got involved  they want to rip you off for £150 to buy a copy when it used to be a free download

[.RC.]

What are you trying to do?

From what I understand you can not run a house that has a RCD fitted, with a generator with a RCD.  When I say run, I mean correctly run with a proper changeover switch fitted upstream from the house switchboard. The RCD will simply click down.

Not one of those murder cords you plug into any wall socket, allowing you to kill line workers who might be fixing downed power lines.

[mikeselectricstuff]

The only way that an RCD will be any use is if the generator has an earth rod linked to  the neutral (or a centre-tap) prior to the RCD.
Otherwise it is impossible for there tp be any current imbalance.

It could be argued that leaving it floating can actually be safer in some situations, as you then need two seperate faults for any leakage current to flow, though one fault scenario in this case is is that the whole of the generator frame becomes live.

[Simon]

What are you trying to do?

Run one machine from one generator for 2-4 hours.

[Jeroen3]

One of the common failures in designing and wiring backup power installations is not doing the grounding and neutral bonding correctly.
https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html

As seller of small generators, providing the earth point and RCD is enough. You can't force the user to install them.
I have an honda eu10i but do not recall it having an RCD, manual does say to wire up ground. Can't say I've done that ever.
It does say

Connect a RCBO (Residual current circuit breaker with overload protection) of 30 mA ground fault detection and cut-off of less than 0.4 seconds at more than 30 A of output current, if you are using two or more appliance.

Some big generator containers do active earth impedance checks with multiple ground rods on each side of the unit. This makes it less likely the user can just tape them together and bypass the detection.

[Simon]

Up until now we had RCD's fitted to the equipment. These apparently failed the EMC test, so we took them off. In my mind the supply should have the RCD not the user. The generator has a bonding point, I doubt customers use it so the RCD will do little. We are going to supply an RCD that comes off the shelf wired into a short extension.

What is live or neutral on a generator that is not bonded? if the live were to become exposed it would harm no one until a secondary connection was made to earth so that current can flow. if what we normally chose to use as live were bonded to earth then it would be the neutral and cause lots of confusion and trip any other protection possibly in the machine.

I have a solar inverter connected to some panels that were just on the ground. A connector was damaged and it tripped. This was a transformerless inverter so they wanted to do the impedance check.

[mendip_discovery]

Up until now we had RCD's fitted to the equipment. These apparently failed the EMC test, so we took them off. In my mind the supply should have the RCD not the user. The generator has a bonding point, I doubt customers use it so the RCD will do little. We are going to supply an RCD that comes off the shelf wired into a short extension.

This would be what I would do. Its adds a few ££ to the cost but it means that people won't growl at you for not having one. Hopefully you would get an off the shelf unit with a good EMC report.

The issue I have with some of the standards is that they are often written for a specific case and then they are vague about it leaving you wondering if it applies to your case or not. You could ask 5 experts and they would give you 5 differing answers, 6 if one of them is an engineer.

[Simon]

The off the shelf RCD is CE marked.

[Jeroen3]

How can a passive device fail EMC tests?

[Simon]

no idea, the RCD was fitted to a power supply

[mikeselectricstuff]

How can a passive device fail EMC tests?

Some RCDs have active circuitry. Could also be an intetaction between the rcd (e.g. current transformer inductance)and the product

[Simon]

Yes it was the fact that the RCD was a coil added in series with the load and it emitted from the RCD. Taking it out resolved it.

[coppercone2]

I think you should put a mallet and a grounding rod as part of the generator setup kit

or those fancy grounding rod hammer drill attachments.

[Simon]

so when you are in the middle of a junction in London what do you do? smash up the highway to get your earth?

[themadhippy]

so when you are in the middle of a junction in London what do you do? smash up the highway to get your earth?

[Simon]

Yea, I guess that would work, should we supply the bucket and the dirt too? what about a complementary 2l bottle of water with replacements sold at £50 each?