Steptoe
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Everything posted by Steptoe
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Dual busbar under the RCBO, and DP RCBO with the same form factor as a normal MCB, But you won't ever see these in the sheds.
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Ye, its one I use to show customers of how tidy they can be.
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Regarding defining TN , TNC, TNS, TNCS, PME. When anyone fails to grasp just how important the correct terminology is, it can be the difference between life or death.
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The IEE or IET do NOT make any regulations that anyone has to follow, BS7671 is non statutory, EAWR is STATUTORY however, and those are what we must work to, Jeremy, its not intended as a direct 'go' at you, it is merely intended to prevent people making erroneous judgements that may lead them to having a dangerous or unsafe electrical installation. OK, so back to EAWR, you can download it for free as its a statutory document, A few quick ones you may wish to look at, Reg 16 : probably the one regulation I quote more than any other, its self explanatory. A few others worth a look, BTW, its not a big book if you just get the guidance version, so well worth a read, Reg 3 part 57-60 Reg 4(3) Reg 5 part 86
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A picture of a board with DP RCBOs, Not mine BTW, but loads of room.
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DP ISCO are quite permitted in the regs, but I would only ever fit them as a last resort and space really was that tight, they are a smidge smaller than 2xSP blocks, but not by much, Also, SP gives you the option of entering either end , (oh err,), Your isolator switch should be between the block and the meter anyway, so that should provide isolation even when sealed.
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We actually bought our house in December 2007 too, We've seen about 30% gain, So I think you've been a tad unlucky,
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A board filled with DP RCBOs will actually be a lot neater and tidier than SP ones due to LESS cables inside, and, they can be got in same form factor as an MCB.
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@Ferdinand has an ISCO with both Line and Neutral cables being connected, These are very prone to cracking inside , then the next time someone knocks it, or tries to remove the cover,,,,,, Prepare to meet your 40 virgins,
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As long as its not a DP Henley (proper name ISCO btw) , like that widowmaker @Ferdinand has
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Just noticed this, And it may be something that most of you don't realise, The actual tripping current is a bit of a red herring here, It could actually be rated the same, or lower than the other devices, Its the tripping time characteristics that are important here, Simply using a 'normal' 100mA RCD will not provide any discrepancy with a 30mA RCD or RCBO, You require one with a Selective or Time Delay inbuilt (S) or (TD)
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100% correct TN-C-S and a claimed PME system (they aren't always) , but they have to state them as such to comply with ESQCR TBH , most new installs are actually proper PME, well, the new bit anyway.
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But I think it further reinforces the fact that a little knowledge can be a dangerous thing, What was being described was a TN-C-S system with localised PME, which is entirely different from TT, One is completely acceptable, the former requires a lot more understanding than just banging a rod in and measuring the resistance, The other misunderstanding was it was said to be impedance being measured, which would be a TN system, so again, not TT as is now being said. These things aren't just pedantic terms, they are lifesaving systems, and it is of vital importance to get them correct.
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Can you post a picture of your cutout,? ie, the incoming supply fuse and cable.
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You said your workshop was TN-C-S, that's why I said adding a rod to it was a half hearted bodge at a localised PME, So, all this pedantic talk of earthing types and terminology actually has a point.
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@JSHarris I didn't imply anything, I just said it wasn't proper. And being qualified doesn't make you competent or knowledgeable, you should know that.
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The DNO are obliged to make all new TN-C-S connections as PME
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If this isn't allowed please delete it, but here is a link to a post I wrote a few years ago highlighting the basic differences in earthing systems https://talk.electricianforum.co.uk/topic/14481-simplified-earthing-arrangements/#comment-202531
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I don't see it being pedantic at all, there are 4 totally different earthing systems in general use, Here's a basic drawing , you can clearly see the differences, so how can anyone possibly say its being pedantic, trying to say they are the same is just being ignorant of the facts.
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Sorry @jack Being so close to the substation brings with it the possibility of the prospective fault current being extremely high, although the DNO will usually state they have measures in place to stop it rising above 16kA, most domestic consumer units are rated at 16.5 , so that's OK, and the main cutout fuse will be rated much higher, the issue can arise with domestic MCBs only being rated at (usually) 6kA, you are now reliant on the main incoming fuse of probably 80a and rated at 88kA to clear the maximum fault current possible. As for the PME and no rods in place, Jeremy's neither meets the formal, or practical definition of PME, although he has sort of (for want of a better word), bodged a bit of a half headed attempt at it , even though he thought he was doing it for an entirely different reason. this can be a serious issue under certain fault conditions, lethal actually, especially when combined with SP protective devices, remembering that 50mA can kill, and that's why the 30mA threshold. 100mA devices are only there to protect against fire, (etc) , not to preserve life. I done a drawing a few years back of simplified earthing basics, I'll look it out.
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DP RCBOs in single gang can be had for less than the price of some SP ones . If you are that close to the Tx your PFC may be a concern,,,,, OK, slight misconception about PME and TN-C-S , PME must be TN-C-S , TN-C-S is not necessarily PME, although it should be, and if you do NOT have a rod at the incoming point, then you do NOT have PME,! FACT,! no matter what you or anyone else says, PME must be rodded at point of entry.
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I'm nor sure you have the correct terminology, TN-C is not permitted in the UK, So its either TN-C-S or TN-S, and unless you have a separate supply to the workshop, it must be TN-S, by default, although as its a submain, then generally regarded as such and the source is the type supply. Also, putting a rod at the remote location has absolutely nothing to so with lowering the impedance, rods are measures using resistance, but again, that's totally irelevany here as well, mostly, you should also have a rod at the incoming supply btw, The reason for the rod is to ensure the potential of the earth is the same potential as the general mass of earth, its something a lot of 'electricians' don't understand either, so your misunderstanding of it is forgiveable, but you really need to rod the incomer , and, preferably, where the submain exits the EZ as well, Is your upfront RCD a 100mA TD,? in order to get discrepancy,.?
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STROMA certification.
Steptoe replied to TheMitchells's topic in Regulations, Training & Qualifications
@JSHarris I don't understand which you just didn't do the 17th exam, Its got to be one of the easiest exams ever, I know of know other test where they let you take the answer book in with you, lol, I like SWA, its almost as nice a job satisfaction as pyro, but that's a different thing altogether. Was your guy an electrician or an installer,? -
What's a 17th es split box,? If your RCBOs are SP then you have less compliance with 17th edition amd3 than a dual RCD CU, and they are not in total compliance either , but generally accepted as the norm. Folks do tend to fit RCBOs tho due to being miseducated about their benefits, and not understanding the drawbacks or dangers of the neutral not being disconnected, Totally non compliant in TT, and just plain lethal in TN with reverse polarity or dropped neutral.
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Yep, its fairly common now to have them fitted, REC2 or 2S for single phase.
