RCD's and portable generators - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: July 10, 2023, 12:01:24 pm
content: This relates to the UK, EU and USA, I know standards may differ. Does a portable generator require an RCD?

author: themadhippy
author_rank: Super Contributor
timestamp: July 10, 2023, 01:03:35 pm
content: any helphttps://electrical.theiet.org/wiring-matters/years/2020/82-september-2020/mythbusters-6/

author: Simon
author_rank: Unknown
timestamp: July 11, 2023, 08:27:21 am
content: 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?

author: Jeroen3
author_rank: Super Contributor
timestamp: July 11, 2023, 09:00:59 am
content: 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.

author: Simon
author_rank: Unknown
timestamp: July 11, 2023, 01:56:31 pm
content: 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.

author: themadhippy
author_rank: Super Contributor
timestamp: July 11, 2023, 02:52:22 pm
content: QuoteThe answer should be in the big book of rules under definitions,from memory an installation is an assemble of electrical equipmentQuotewhilst 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

author: .RC.
author_rank: Frequent Contributor
timestamp: July 12, 2023, 10:06:46 am
content: 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 12, 2023, 10:17:49 am
content: 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.

author: Simon
author_rank: Unknown
timestamp: July 12, 2023, 12:18:47 pm
content: Quote from: .RC. on July 12, 2023, 10:06:46 amRun one machine from one generator for 2-4 hours.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 12, 2023, 12:29:29 pm
content: 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.htmlAs 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 sayQuoteSome big generator containers do active earth impedance checks with multiple ground rods on each side of the unit. This makes itless likelythe user can just tape them together and bypass the detection.

author: Simon
author_rank: Unknown
timestamp: July 12, 2023, 02:49:16 pm
content: 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.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 12, 2023, 04:55:08 pm
content: Quote from: Simon on July 12, 2023, 02:49:16 pmThis 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.

author: Simon
author_rank: Unknown
timestamp: July 13, 2023, 06:32:04 am
content: The off the shelf RCD is CE marked.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 13, 2023, 07:05:13 pm
content: How can a passive device fail EMC tests?

author: Simon
author_rank: Unknown
timestamp: July 13, 2023, 07:36:56 pm
content: no idea, the RCD was fitted to a power supply

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 13, 2023, 11:11:19 pm
content: Quote from: Jeroen3 on July 13, 2023, 07:05:13 pmSome RCDs have active circuitry. Could also be an intetaction between the rcd (e.g. current transformer inductance)and the product

author: Simon
author_rank: Unknown
timestamp: July 14, 2023, 07:53:56 am
content: 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.

author: coppercone2
author_rank: Super Contributor
timestamp: July 17, 2023, 09:22:26 pm
content: I think you should put a mallet and a grounding rod as part of the generator setup kitor those fancy grounding rod hammer drill attachments.

author: Simon
author_rank: Unknown
timestamp: July 19, 2023, 05:13:22 pm
content: so when you are in the middle of a junction in London what do you do? smash up the highway to get your earth?

author: themadhippy
author_rank: Super Contributor
timestamp: July 19, 2023, 05:17:34 pm
content: Quote

author: Simon
author_rank: Unknown
timestamp: July 19, 2023, 05:19:48 pm
content: 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?