32A RCBO for sockets in industrial setting

Question

i have a customer who has 32A sockets on an injection moulding machine. They are protected by RCBO, however, due to the heating controllers that get plugged in, they pretty much trip as soon as the heats are turned on. This means they then have to plug the box in to an older machine next door which is protected by MCB. Am i right in thinking that with the correct Risk Assessment that the RCBO could be swapped out for an MCB? Any advice greatly appreciated.

lyledunn · Accepted Answer

gkenyon said: b) At Section 12.4.3, risk assessments for omission of 30 mA RCD protection. In this, case, you might be able to weigh up whether risks in maintenance are increased by 'hard wiring' to a fixed switch-disconnector, rather than connecting via plug and socket-outlet ... but importantly, you will need to include the relevant dutyholder in the risk assessment. 
 In certain situations, perhaps like this one, inclusion of an RCD would likely introduce a greater risk. Motor swap out can be done easily, efficiently and safely to allow minimal downtime for this dockside unloading arrangement.

Newfutile · Answer

That would suggest a fault in the machine to me,unless the equipment manufacturer states it has a high protective conductor current,is this class 1 equipment?

Chris Pearson · Answer

You may be able to take advantage of the exception in 411.3.3, but only if the equipment is used by instructed or skilled personnel. Note 1 is important. 
 This changed with Amd 2.

mapj1 · Answer

If these are mineral insulated heating elements it may be normal, but it may be an early warning of an insulation failure. 
 It may be worth checking the heaters. 
 The RCD may be omitted if the cable routes do not require RCD protection, being visible or in conduit or SWA etc and 
 1) the machine was hard wired, or 
 2) if the socket was 63A or above, and or where ordinary persons do not use it, and there is a documented reason and RA that describes how the risk is mitigated to an equivalent level by other means. It is very clear that is not the preferred route, although of course with older kit and older situations it is quite a common situation. 
 generally, additional protection by an RCD not exceeding 30 mA is required, 
 1. Socket-outlets with a rated current not exceeding 32 A in locations where they are liable to be used by persons of capability BA1, BA3 or children (BA2, BA3) 
 2. Socket-outlets with a rated current not exceeding 32 A in other locations 
 3. Mobile equipment with a rated current not exceeding 32 A for use outdoors 
 There is now no mention of a domestic caveat, as all installations are treated the same, and the socket-outlet rated current has increased to 32 A, from 20 A. 
 The key part is that where any BA1, BA2 or BA3 persons are liable to use any such socket-outlets. These capability identifiers are as follows: 
 BA1 &ndash; Ordinary person (non-electrically skilled or instructed) 
 BA2 &ndash; Children 
 BA3 &ndash; Disabled persons 
 These categories are external influences, and a full description of them and other influences that may affect an electrical installation can be found in Appendix 5 of BS 7671:2018+A2:2022. 
 Can we still omit RCDs? 
 We can still omit an RCD, but only for indent (2); however, there must be a risk assessment for each socket-outlet that is to be omitted from RCD protection. Any risk assessment must be fit for purpose and adequate for the individual installation and its use. It&rsquo;s for this reason the Client, duty-holder or user of the installation carries out any such risk assessment. 
 Mike

Chris Pearson · Answer

Gavin Sayers said: I suppose the question would be, are the persons using the sockets electrically skilled/instructed enough to be deemed competent to use? 
 The real question is whether you can properly justify the additional risk of not having additional protection. For me, the avoidance of "nuisance tripping" is not adequate justification. 
 Note 1 to 411.3.3 says, "For the purpose of this exception, an ordinary person (BA1) instructed in the use of the installation does not become an instructed person (electrically) or cease to be an ordinary person." 
 I think that these exceptions should be pretty rare nowadays. An example might be in an electrical workshop (or laboratory). So, fault finding by an instructed or skilled person may be impossible if the socket has additional protection and the fault is causing > 30 mA of "leakage".

mapj1 · Answer

In terms of technical mitigation the problem is that with high CPC current the 'single fault' of loss of CPC continuity in the flexible lead would lead to an immediate danger of shock from the case of the equipment. 
 Is there for example something that would allow an additional earth bond, so two independent things have to fail before there is danger, restoring a more acceptably unlikely level of risk. 
 Does it need to be plug and socket, or could the wiring be mechanically fixed, or the plug locked in ? 
 Ordinary persons become instructed, once they are aware of, and can understand, the risks. 
 reading and understanding something like this would be a good start. 
 https://kmelectric.com.au/importance-of-the-earthing-system/ 
 
 Then they need to know they should report any tingles or other funny behaviour, and who to report it to, and perhaps how to verify things are all right (how to check cables etc ) before plugging in . 
 And you need to keep non-instructed persons away ;-) 
 Some organizations use pro-forma paper work Example here. 
 https://select.org.uk/common/uploaded%20files/Technical/FreeDownloads/SELECT_RCD_form.pdf 
 
 Mike

mapj1 · Answer

I wrote a reply that the software seems to have lost, here is another go. 
 The thing that makes it dangerous, is a failure of the CPC in the flexible lead or plug - with a high leakage this becomes immediately dangerous rather than an early warning picked up on inspection. 
 The normal UK/ EU paradigm is double fault to danger - that is to expose a user to danger, two independent things have to go wrong - e,g, CPC and an insulation failure (for type 1 earthed things), or external and internal insulation (for type II double insulated kit,.). 
 It is now common to add a third layer , "and an RCD failure" before a lethal shock is possible - a 3 layer 'defence in depth' approach if you like. 
 So as well as instruction, which means understanding the risks and how to check for them, not just how to use the kit normally, there needs to be a mitigation that you can, hand on heart say restores a similar level of safety. 
 That may be making the damage unlikely (fixed wiring or enclosure) or assuming it may occur, but there is a second earth path - perhaps a fairly chunky extra earth bond. But the users need to know why it is important and what sort of disconnection or damage to check for, and that they must report any tingles etc Some outfits use a pro forma RA https://select.org.uk/common/uploaded%20files/Technical/FreeDownloads/SELECT_RCD_form.pdf I'm not sure how useful that is. Mike.,

gkenyon · Answer

IET Guidance Note 5 Protection against electric shock provides some insight into how to deal with: 
 (a) At Section 12.4.5, high protective conductor currents so that socket-outlets can be protected by 30 mA RCDs. Particularly, this equipment is machinery as defined in the Supply of Machinery (Safety) Regulations, and the method outlined in 12.4.5(c) of Guidance Note 5 is actually included in the relevant product standard (Clause 8.3 of BS EN 60204-1:2018+A1:2025). Ususally, where machinery has high protective conductor currents, suitable labelling and instructions are provided by the manufacturer according to Section 8.2 of BS EN 60204-1:2018+A1:2025 . (b) At Section 12.4.3, risk assessments for omission of 30 mA RCD protection. In this, case, you might be able to weigh up whether risks in maintenance are increased by 'hard wiring' to a fixed switch-disconnector, rather than connecting via plug and socket-outlet ... but importantly, you will need to include the relevant dutyholder in the risk assessment. BS 7671 does permit 'hard-wiring'; to switch-disconnectors, though ...

32A RCBO for sockets in industrial setting

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