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DIY Forum >> Electrical Questions >> Safe Zones https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1229803548 Message started by wozzy on Dec 20th, 2008, 8:05pm |
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Title: Safe Zones Post by wozzy on Dec 20th, 2008, 8:05pm from the permited cable routes section in the OSG 7.3.2 (16th edition) a safe zone is created horizontally from the acessory, is does not have a limit on the length of this safe zone. does this mean it is accepted that this zone is unlimited in length?? |
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Title: Re: Safe Zones Post by The_Trician on Dec 20th, 2008, 8:12pm Yep, other than the length of cable for volt-drop purposes. |
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Title: Re: Safe Zones Post by wozzy on Dec 20th, 2008, 8:20pm seems a bit stupid to me that it can be unlimited, does this zone include going around corners that are 90 degress (as it appears in the on site guide) such as in a conservertory? |
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Title: Re: Safe Zones Post by cosbycarl on Dec 20th, 2008, 8:30pm yes, but these cables have to be mechanically protected and earthed, or rcd protected to prevent the people that dont know, from hurting themselves or worse, unless of course your gonna install ya cables more than 50mm deep, but it is as you read it in the OSG. |
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Title: Re: Safe Zones Post by Lectrician on Dec 21st, 2008, 8:45am wozzy wrote on Dec 20th, 2008, 8:20pm:
NO - The zones do not go around corners. In conservatories in the past I have placed a socket on each wall for this very purpose. |
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Title: Re: Safe Zones Post by wozzy on Dec 21st, 2008, 10:06am how stupid of me, i meant to wirte 'that are not 90 degrees'. the on site guide shows the zones in a corner of a room. i used a conservatory as a example as they often have walls that are not at 90 degress usually 45 or less sometimes. The whole safe zone diagram i have a problem with, does anyone actually install cables in some of these zones? such as in the corners of rooms, or within 150mm of the top of walls? where there is no indication that cable could be there? |
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Title: Re: Safe Zones Post by greg on Dec 21st, 2008, 10:13am I think the thing with prescribed zones is that if you run cables within 150mm of ceiling / corners, its not often that anything will be fitted to these areas that requires drilling (except kitchen corner units). With runs to an accessory, people should check which way the cable is running, as regards horizontal runs, you can't run horizontally through every room in the house to an outlet at the very back of the house without offering additional mechanical protection unless there is an outlet in each room to show that there could be a cable running horizontally to it. |
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Title: Re: Safe Zones Post by wozzy on Dec 21st, 2008, 10:24am i can see where these zones are derived from, but i think there are plenty of thing that go in corners and tops of walls that require drilling, just walked round the house and found quite a few. My question is does anyone use these less obvious zones on a daily basis? i know i dont, just wondering if anyone does? |
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Title: Re: Safe Zones Post by Lectrician on Dec 21st, 2008, 10:27am I would only use them in exceptional circumstances, and even then only if there really was no other way. Things fixed in corners? Coat racks close to the wall, speakers in the corner of a room, corner shelf's for plants, curtain tracks etc. The NIC did an article on the top 150mm rule. They had some statistics which commented on plasters fitting coving and using nails to support the coving while the adhesive goes off. You see this regularly. |
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Title: Re: Safe Zones Post by greg on Dec 21st, 2008, 5:54pm wozzy wrote on Dec 21st, 2008, 10:24am:
It would never be my first choice |
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Title: Re: Safe Zones Post by scotspark on Dec 21st, 2008, 7:55pm only time i use the safe zone at the top is conservatories with a light pendant type fitting straight up from switch - up angle of roof behind plasterboard - along roof pitch behind pvc and thats rarely as most go for wall lights or switched lamp sockets |
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Title: Re: Safe Zones Post by wozzy on Jan 17th, 2009, 5:35pm [edit]Be aware that this link is to some information from the 16th edition of the regulations, not the latest 17th edition. Admin.[/edit] http://www.voltimum.co.uk/cm.jsp?action=view&cat=53&universe=consult.experts_hottopics.bs8436 second link down, the document lists cables that are permitted for use ouside of safe zones. This document is quite old. Am i right in thinking these types of cables suitable to be non RCD protected and buried in walls?? or have i got it completely wrong? |
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Title: Re: Safe Zones Post by cosbycarl on Jan 17th, 2009, 6:48pm wozzy wrote on Jan 17th, 2009, 5:35pm:
MICC and Armour dont need rcd protection whether they are surface or buried at what ever depth, but that depends on what circuits they are supplying and in which type of installation (domestic, commercial, industrial), i.e sockets being used by unskilled persons rated less than 16a for general use or for use outside by portable equipment etc... Also for circuits supplying current using equipment in a bath or shower room (probably wouldnt see that so much), a cooker circuit with a socket incorporated within it etc.. and/or if the installation is TT. Normal T&E cable needs rcd protection if buried less than 50mm, but doesnt if buried more than 50mm or mechanically protected by earthed metallic covering, again thats dependent on what circuit its supplying and if TT. Split Concentric cables cant be used as they are treated the same as T&E, for what reasons i dont know, i remember lec mentioning it on another post back along. Armour, MICC or t&e incorporated within an earthed metallic covering would be good for installation outside of prescribed cable zones. |
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Title: Re: Safe Zones Post by LSpark on Jan 18th, 2009, 9:11am Not Concentric - they are not permitted to be used on installations. Split-concentric is a different matter. |
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Title: Re: Safe Zones Post by Lectrician on Jan 18th, 2009, 10:08am Split Concentric cables CAN NOT be used out of a safe zone - Thats why I say treat it as T+E! |
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Title: Re: Safe Zones Post by wozzy on Jan 18th, 2009, 10:54am sorry i didnt post that very well, the second link down opens a page on that page you will find the link to a pdf NICEIC - BS 8436, Concealed Cables PDF (51Kb) have i read that document wrong as the cables listed at the bottom range from armoured to stuff that looks like FP200 when i google it! |
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Title: Re: Safe Zones Post by Lectrician on Jan 18th, 2009, 11:15am wozzy wrote on Jan 18th, 2009, 10:54am:
Your link is to a very old edition of the "Connections" magazine, which was written in the times of the 16th edition ;) |
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Title: Re: Safe Zones Post by Lectrician on Jan 18th, 2009, 11:20am The NIC have stated that FP200 is not suitable for use out of zones, however, FP400 or it's equivalent is fine to use. FP400 is basically armoured FP200. |
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Title: Re: Safe Zones Post by wozzy on Jan 18th, 2009, 11:38am i was told that when i went to a NICEIC 17th edition seminar. I cannot find a mention in the 17th 522.6.6 for cables complying to BS8436. My reason for all of this as on another forum i visted it was suggested that a cable to this BS could be installed outside of a safe zone. As there is no mention of this number in the 17th 522.6.6 does this mean this type of cable is now obselete? http://tpwcc.com/flexishield.html |
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Title: Re: Safe Zones Post by LSpark on Jan 18th, 2009, 2:44pm Lectrician wrote on Jan 18th, 2009, 11:20am:
Why would anyone pay all that money and put in FP400 fire RESISTANT cable to solve the zone/RCD issue when an RCD would still be required for almost all socket outlets. Most people would not even install normal SWA, let alone some fancy FP cable. At least if your house burns down and you install MICC you'll have something left to salvage ;D |
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Title: Re: Safe Zones Post by Lectrician on Jan 18th, 2009, 4:21pm I assume you would use FP400 if you required it to be fire proof........the supply to a fire alarm being run out of zones for example ;-) |
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Title: Re: Safe Zones Post by LSpark on Jan 18th, 2009, 7:24pm Indeed. But most situations that bring up the topic of zones are in relation to normal domestic situations, where the budget won’t stretch to that type of cable. Ideal though for residential accommodation, HMO's etc |
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Title: Re: Safe Zones Post by Goodsparks on Jan 19th, 2009, 7:59pm 7671 - Page 100 reg. 522.6.5/6 Flexishield (TPWCC) 300/500v is to BS 8436 and can be used outside of the safe zones. 2c 1.5mm is around £60 / 100m Pirelli LSX, IDH Guardian, Pyrotenax Multiplus, Nexans Alsecure are all the same stuff and pass the same ERA 'nail penetration' test but are generally rated at 600/1000v which puts them outside of the scope of BS 8436. Paul |
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Title: Re: Safe Zones Post by wozzy on Jan 20th, 2009, 7:31pm i read that reg a few times and still missed that BS number in the reg, i think that says quite alot about how i read |
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Title: Re: Safe Zones Post by LSpark on Jan 20th, 2009, 7:36pm Says more about what you read than how you read Wozzer ;D GS, LSX is just standard FP cable, or did I miss something?.. it's certainly not nail proof! |
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Title: Re: Safe Zones Post by Goodsparks on Jan 20th, 2009, 11:26pm Quote:
LSX isn't FP. FP maintains electrical integrity when exposed to heat/fire/water and produces limited harmful emissions but the insudite insulation only has a 70 oC operating temperature (for circuit design / cable calcs). The aluminium foil screen is designed for emc shielding and is not of sufficient thickness to withstand the fault current necessary to operate a 32a type B mcb when penetrated by a nail. LSX (and all the others listed) do not maintain electrical integrity in a fire and cannot be used for life safety services, the live conductors have XPLE (thermosetting) insulation (90 oC so 32a radials possible on 2.5 2c) The aluminium screen is thicker and will withstand the fault current required to trip the 32a MCB. The cables are generally LSF so are good for use in exposed public areas where poisoning isn't really an option. The requirement for concealed conductors isn't to be nailproof, but to safely disconnect the supply when hit with the nail. www.prysmian.co.uk/export/sites/prysmian-enGB/attach/pdf/Afumex_LSX.pdf - Paul |
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Title: Re: Safe Zones Post by LSpark on Jan 21st, 2009, 9:06pm Interesting, I only say because I'm sure I noticed LSX markings on some pirelli FP type cable. I'm going to have to do some research now!. Tis all your fault ;) |
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Title: Re: Safe Zones Post by wozzy on Jan 23rd, 2009, 7:39pm 2c 1.5mm is around £60 / 100m where you get this price from? i was quote £130!!! plus VAT |
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Title: Re: Safe Zones Post by Goodsparks on Jan 24th, 2009, 9:17pm Cleveland cables for flexishield or Batt for IDH Guardian. Paul |
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