Comment about using non swa glands with swa.
- NICEIC fail such installations (then or later PIR)
- BCO visual inspection check for non swa glands (perhaps new spies :-)
Argument being swa bs type approval requires bs type approved glands for swa.
For pme-to-tt swa perhaps consider swa glands into plastic box; type-approval of swa maintained, but house earth is not exported.
Just a comment.
Fair comment ... good to know I'll terminate using standard brass glands, in a plastic box in the outbuilding ... and insulate the gland, probably with industrial heatshrink over the normal plastic shround.
yup
yup
You will need RCD protection for all circuits - including lights - since the earth fault loop impedance may be too high to open a MCB on an earth fault in the garage. You could do this with one 30mA one if the loss of lights on a trip is acceptable, else use individual RCBOs.
100mA with time delay... like:You can. You would just have more earth fault protection on the submain than would actually be required.
You could do this, and you would not need the separate RCD in the outbuilding. However you get no discrimination again, and this time you have to walk back to the house to reset it.
Not if the submain has 30mA RCD protection at the head end. Its the cheapest but least elegant way of doing it really.
you put it in, no harm would come, but you could find the RCD at either end could trip (or both) on a fault)
To clarify, I was not suggesting use of a non SWA gland - but use of an exterior "3 part" one one even though it would not be required for its waterproof characteristics. (having said that many interior ones come with the PVC boot anyway).
However this does seem to be a case of being between a rock and a hard place... the brass gland will make the PME earth accessible in the outbuilding (albeit will very limited contact opportunity since I doubt many people spend much time fondling their glands in the garage). Is there a SWA type approval?
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I haven't fondled my glands in the garage for a long time :-0
Thnaks for the help ... at least I can run the cable in now and close the trench.
That's most likely to ensure a good connection to the armour, which is specifically not wanted in this case.
I would not use a metal SWA gland at all in this instance. If you want to use a gland, use a plastic one. However it no more needs a gland than any of the other cabling going into the CU. Cut ends of the armour need insulating though, and a plastic gland could be a good place to have them.
Indeed - and agreed, however it is one nit-picked area.
Favoured to stop PME earth appearing inside same enclosure as TT.
arguments against... a) swa bedding not intended to be exposed outside enclosure (not sheath) b) swa bedding not intended to be clamped by stuffing gland (not sheath) c) swa must be terminated by swa gland at entry to enclosure citing a) b) d) use of non-swa gland exposes bedding to cut armour on cable movement/vibration
Specific example of d) was 3-core 4mm - bedding is p*ss thin against cut armour.
arguments against... a-d) deviations no longer apply, unfortunately PME earth now inside same enclosure as TT (same as proper swa gland)
arguments against... a-d) deviations no longer apply, PME & TT earths separated by enclosure. Unfortunately your swa-gland has a brass body at PME potential separated by the plastic gland shroud. Fine, until the event of host PME losing its neutral, whereupon that brass body becomes 240V.
Hence the desire for plastic gland. Just a comment re some nit-pickers go ape seeing anything but swa- gland on swa.
Aside, if TT end remotely wet use plastic rotary 1P/3P+N IP65 isolator (DIN cpd enclosure is high IP-rated until you open the door to isolate something or reset a CPD). Easily padlocked off if fixed rotary tools anywhere, kids about, sawing your sister in half gets messy.
FAOD I wasn't for a moment suggesting that.
True, although the situation is little different from the use of a stuffing gland to anchor a flexible cord.
That is what I was suggesting, and can't really see any problem with.
So what? Which regulation(s) in BS 7671 does that violate?
- It's inside an enclosure only accessible with the use of a tool, so basic (direct contact) protection is achieved.
- Nothing is connected to it.
- It's anchored by the gland so can't move around and short to anything.
- In addition to the above three points you've insulated it with heatshrink. That's site-applied insulation I suppose, but it would seem OTT to suggest it needs testing.
- The neutral incomer is also inside the enclosure and that's electrically the same point, and would be just as 'live' in the event of an o/c neutral in the DNO's network.
Agreed: unsatisfactory, since the shroud can be removed without the use of a tool; also the creepage & clearance distance where the shroud abuts the box is inadequate.
I don't doubt that, but they must be able to justify their decisions by reference to BS 7671. What does the NICEIC technical manual have to say on the subject?
Of course, I used "1." to show how they suggested "2." & then "3.".
Neither can I and it is common in industry.
None, I could not find anything either. That inspector insisted on swa gland for swa into plastic box. Other contractors insisted "rectifying" to swa gland into plastic box.
The belief being that the plastic enclosure "stops PME contact". They did not consider the "shroud does not require tool for removal".
Exactly. Shroud removal exposes PME earth to anyone in the TT install.
I suspect miss-application of 511-01-01 re intended purpose. Yes the intended purpose of an swa gland IS to terminate swa. However a more important need is preventing PME sitting on the outside of your enclosure in a TT install, which necessitates a plastic gland.
Unknown, it would be interesting to find out.
My suspicion is that they would say the plastic gland ("2.") complies. I hope they would also state that "3." fails for the reason given.
A case of using a plastic gland, but if challenged cite the shroud.
Just put the whole thing in a bigger box and screw the lid down.. then it needs a tool. ;-|
I'm not really sure where this leaves me ...It seems I can't use a plastic gland as it will not meet BCO requirements .. if I use a brass gland it is potentially dangerous unless the connection is modified.
a) Terminate using a brass gland .. and if I then heat shrink a full industrial sleeve over gland - is that 'acceptable' (better than push fit pvc sleeve) - and accept armour wires are within enclosure - but not terminated
b)Terminate using brass gland .. but making connection on top bedding not the wires - is that 'acceptable' - seems poor practice.
b) Terminate with a plastic Gland
Or perhaps a solution is terminate fully as normal but within a separate plastic box (that needs tools to open) and then take only L&N into the CU. Presumably this meets BCO requirements and is also safe ?
Terminate as A.Wade suggests with a plastic gland (listed as "2." in my comment).
In the future if anyone says you should use a "proper SWA gland in plastic box" point out to them that doing so would leave a "non-tool removable shroud as the only separator between a TT install & PME brass gland underneath". Stick that on a bit of paper in the box - just something to know if someone demands an SWA gland :-) No chance of it, but at least you are prepared to send them away to actually think rather than kneejerk.
Some installation comments...
Leave a "repair loop" in your swa
- that way you can redo terminations or gland without having to replace a cable
Cable should be at a depth appropriate for ground usage
- ploughed field 1.5m or more, typical domestic 0.45m
Cable should be laid in a suitably prepared trench
- trench free from large stones, cable laid on a bed of riverwashed sand
- 150mm of riverwashed sand above, then yellow cable marking tape, then backfill
Cable route should be documented somewhere
Watch cutting bedding around insulation, 4mm 3-core is often very thin above the cores
- easy to nick the insulation which will fail a visual inspection if not an insulation resistance test also
- it is for this reason that repair loops are a very good idea
Nuffin to it, its the digging that will hurt the following morning.
Note that "BCO requirements" will vary with the BCO. So you may as well do it according to BS7671 and worry about what any BCO might say later (and if they want to argue, ask for supporting paragraphs from 7671).
which is what ? .... terminate is plastic gland or metal ? .... not being facetious, just want to get it right.
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