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Post Time: 29/01/2008 12:40:50 |
krishna
Total Forum Posts: 9 |
Our house needs a complete rewire while we carry out refurbishments. It was last rewired in the 1960s! Anyway, I have spoken to an electrician about the Powerwatch suggestions outlined in the house rewiring guide. This was his response.
1. Ring mains - all ring mains would be folded, this is standard. He's actually the second electrician to tell me this.
2. Spurs - he's willing to do spurs if we really want, but advises against it as he says the 20A rating of the spurs could mean big problems. e.g. he claims we would not be able to use an electric kettle and a toaster at the same time. He did say it might be possible to get around this issue by using bigger cable; i.e. 4mm cable instead of 2.5mm, though he wasn't sure if the firecheck cable would be available in that thickness.
Is your recommendation that a folded ring circuit be used in the kitchen and spurs elsewhere?
3. It appears that our electricity supply feed is linked in with our neighbour's. Supply comes into our house and then there is a cable out to next door. Any issues we need to tackle here, while we are at it?
4. When I showed him the picture of the TW950 cable he said he knew what that was. He called it FS..., forgotten the number that followed the FS, but it was something like FS760? Anyway, would that be the same thing? Or should I be insisting on TW950 or Multi-plus?
We want to relocate the meter/consumer unit. Anything we need to take into account in doing this?
Is it better to run cables around the walls (behind the skirting), or under the floor, or does it not matter?
Any comments?
Also, any recommendations on switches and sockets? Does it make any difference what these are made out of? For environmental reasons, I'd like to avoid PVC but not sure if there are affordable options on this.
Another question. What about the cabling from the socket to any electrical appliance? Clearly most of these are standard PVC cabling. Is there an issue with this?
Thanks! |
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Post Time: 30/01/2008 15:12:17 |
alasdairP
Total Forum Posts: 173 |
1. Great, but I am most surprised. As long as he uderstands that the fold-back cable needs to be run as slose as possible to the other end of the ring cable (i.e. they run alongside each other) then that is correct. I would be intetrested to know when they started working this way - I have come across lots of electricians who don't seem to know about this option.
2. Spurs. I would suggest a separate folded ring circuit for the kitchen (+ utility room if you have one) as you are likely to use quite a lot of high-powered appliances there. 3kW (e.g. a kettle or powerful fire or fan-heater) draws 13 amps at 230 volts. Most toasters are 700 watts to 1500 watts (3 amps to 6.5 amps), so a kettle and toaster would be OK on a 20 amp cable. However, we do recommend fold-rings for kitchens, so you have a 30 amp limit there.
2.5 In the rest of the house it is now most unusual to draw more than 20 amps from a socketed circuit. Most appliances now only take a few amps (at most). We call them radials rather than spurs - spurs are short radials taken off a ring circuit. Radials generally run right back to the consumer box. Both are OK and a properly folded ring with occasional spurs to remote places is a good option, if a bit of an over-kill regarding power capacity.
3. You should definitely get the supply separated/split outside your house. I imagine that it is an ex-council house where they often cut corners to save pennies. The electricity company should do this for free - the connection up to the meter is their property and their responsibility and your neighbour's electricity supply should not pass through your house. You may like to think about an external electricity box on the wall so that the meter-reader does not have to enter your house in the future.
4. Cable. TW950 is fine as are some other foil-screened fire cables. However, I have been recently told that for general electrical residential installations there is a screened cable made to BS 8436:2004 - electric cables, 300/500 V.
Screened electric cables having low emission of smoke and corrosive gases when affected by fire, for use in walls, partitions and building voids. I am told that there are a few brands on the market, mainly used in areas where the cable is mounted just under the surface of a partition wall and where nail / screw penetration might be a problem. The cable has a low smoke sheathing. It is subject to a special nail penetration test. The screen of the BS 8436 cable is not intended to address the EMF issue but it does act as an electric screen. Its main purpose is to trigger an RCD in the event of a nail penetration.
The purpose of the foil tape in the TW950 (etc) fire performance cables is to retain the cores together during a fire, when the external sheathing has burned away. Although it performs as a good electrical screen, and potentially as an earth route, it is not intended for this purpose.
I am trying, not successfully at present, to locate suppliers of cable to BS 8436. I will report back here when I find some.
4.5 I would recommend a metal-clad consumer unit. Not much else to say except it is worth trying to locate it in a place that is convenient, not close to chairs or beds and will reasonable minimise wiring to and from the power and lighting circuits. I always suggest that the light next to the consumer box is on a circuit that supplies little else (maybe a couple of other corridor lights) so that if a trip goes, you still have some light to see what you are doing. Or you could take an externally 3A fused spur off a main power circuit to this light only which would save a circuit breaker slot in the consumer box.
5. Cable runs, using screened cable, can be run any which way. However, access for maintenance and future changes is worth thinking about.
6. Few sockets and switches use PVC - most are forms of polycarbonate, I believe. Even the metal-clad ones are plastic underneath. If I had the money, I would tend to have MK as my first choice, either white plastic or metal-clad- plus. MK products are well made and long-term reliable. However other makes are also very good nowadays and are usually cheaper.
7. Cabling from sockets to appliances (etc). Most are PVC (not much you can do about this, though rubber cables are still available). For bed-lights (etc) I recommend flexible screened cable (type CY or SY). For everthing else, I would not bother changing the cables. There are various safety and testing issues to do with electric cords supplied as new with appliances and, unless you are very electrically sensitive, I would leave well alone and just route them away from your feet and legs (etc).
Do ask more questions if I haven't answered everything.
Best of luck with your re-wiring,
Alasdair.
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Post Time: 31/01/2008 02:34:17 |
krishna
Total Forum Posts: 9 |
Thanks for the lengthy reply, Alasdair!
1. I will check that he understands the folded ring requirements and find out when they started working this way (assuming it really is a folded ring!)
2. I'll put to him the spur and ring approach you suggest.
3. Yes it is an ex-council house. So if I ask to move our meter, the elec company will have to pay to move our neighbour's supply? I had originally thought about moving both gas and electricity meters outside, but may have a problem fitting the box to the wall of the house. For the gas, it's still possible to do this, but so far I have failed to find any approved way of installing an electricity meter away from the main wall of the house. Is there a benefit to moving it outside, from an EMF point of view?
4. Thanks for the information on BS 8436. I'll put that to my electrician. From my preliminary searches there seem to be at least two cables compatible with this standard: Flexishield and Pirelli LSX. The former is available from the Cleveland Cable Company, but I don't know who they supply. In looking this up I realise that I think the cable the electrician thought I was referring to when I showed him your wiring guide was FP200. But I'll mention BS 8436 to him and see what he says.
4.5 I think we may locate the consumer unit near the bottom of the stairs, close to ceiling height. Will be out of the way, but accessible from the stairs. And I guess will also be nicely mid-way-ish between ground and first floor.
5. With regards to routing and maintenance, I proposed to the electrician that he route cable behind the skirting rather than across the floor and he seemed baffled by this idea. His argument was that once you rewire it shouldn't need any maintenance for 30 years. I didn't have any clear ideas as to what might be needed, but I did say it may be necessary to change some of the outlets, or add sockets, etc. He said that either way you would still need to lift floors etc., which I don't quite understand. Anyway, I will suggest that he route stuff around the room, behind skirting as much as possible.
6. Thanks for the info on sockets. Didn't realise they weren't PVC. I have always liked MK products myself. Certainly have the best designed plugs. Some of the boxes state they are PVC, but I guess the front plate/switch etc is not.
Thanks again. Might come back to you if I have any further questions after talking with electrician again.
Krishna |
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Post Time: 31/01/2008 19:59:18 |
alasdairP
Total Forum Posts: 173 |
1, 2 , noted
3. Not really. Inside is fine.
4. FP200 is another fire-safe type cable. I believe that it is fine, but BASEC, who test UK cables for approvals puroses, say that BS 8486 is really the correct cable to use for general wiring (if you can get it). Thanks for the hints re who make and sell it - you were more successful than I was.
4.5 Sounds good. An old-fashioned location!
5. It will be harder to route behind skirting as the wall is often of poor quality and you have to avoid the skirting mounting nails / screws. I would go mostly with the easiest runs for the electrician to use. No point in paying for extra time that doesn't really improve the final job.
Good luck!
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Post Time: 07/02/2008 11:51:34 |
krishna
Total Forum Posts: 9 |
Hi Alasdair. Electrician has come back to say Flexishield will cost an additional £200 over the FP200. Is it worth the extra? |
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Post Time: 14/02/2008 13:21:54 |
alasdairP
Total Forum Posts: 173 |
Hi Krishna
No, probably not, but I am slightly surprised. Ask your electrician if it is the actual cable price or greater difficulty in using it that increases the job price by £200. BASEC, the people who formally test the cables, say that the BS8486 cables should be cheaper than the FP200 types of fire-proof cables. I will ask them for more details. Using the officially correct cable might be better for later approvals under Part P if an Inspector was being difficult. I don't know what sort of percentage increase in price on the total job the £200 would be.
I really appreciate you raising these issues. Thanks.
Alasdair
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Post Time: 15/02/2008 22:06:15 |
krishna
Total Forum Posts: 9 |
Thanks Alasdair
I'm not convinced the first electrician really understood what I was looking for in a folded ring. I'm getting another electrician to quote. Thinks I'm mad, but I've given him a copy of your house rewiring guide and he really seems to be taking on board my requests re folding ring and radials. Not had the quote yet. He was finding BS8486 problematic due to supply problems - his wholesaler doesn't seem to stock it. But I've checked with Cleveland Cable Company. They charge 95p/m for 2.5mm twin & earth and 65p/m for 1.5mm cable (+ VAT). Seems to be the best price I have found so far. The other cable I mentioned (Pirelli LSX) is probably unnecessarily robust (600V/100V), but Pirelli do another BS8436 compliant cable called Earthshield. Not checked on prices of this.
Biggest problem is going to be getting our 'daisy-chained' supply moved! I am seriously considering leaving it where it is. Moving meter is going to cause huge time delays and will cost in excess of £600. Clearly it is armoured cable. Runs along the ground under floor (suspended timber) from one neighbour to our meter, and then continues to the other neighbour. Do we need to worry about this cable? Anything we can do short of moving it, or do you strongly recommend moving it? Thing is, I'm not convinced that, even if we have the supply head moved, all the cable will be removed from the house anyway.
Krishna |
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Post Time: 19/02/2008 15:55:32 |
alasdairP
Total Forum Posts: 173 |
Krishna
I have contacted the CEO of BASEC about availablity, price issues and FP-200 FW-950 suitability (again!) etc and will respond back here when they reply.
Regarding the daisy-chained supply: I have talked to Ofgem and Energywatch. Aparently, since privatisation, connections has become an "external chargeable service" that all the copmanies try to avoid picking up the cost of. So, if the wiring is relatively modern and 'reasonably' up to current connection safety standards then any changes would have to be paid by you - it would not be worth it. It would be an "assumed easement" permission. Does the wiring look as if it is like a reasonably modern PVC (or similar) plastic covered armoured cable? If it were an old and sub-standard supply, then the network operators are actually responsible for the supply connection to the meter(s). However, they are not obliged to change old shared connections anymore providing they are safe and they supply an adequate safety earth bonding connection. Have you tried talking to them? What does your new electrician suggest? Probably it is best left unchanged if it seems OK.
It should not give problems. You could ask your electrician to put a clamp-ammeter around it and measure the net current - it should be zero (or close to zero). If more than about 0.1 amps, then further investigation will be required or you may end up with elevated magnetic fields.
Alasdair
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Post Time: 21/02/2008 17:17:35 |
alasdairP
Total Forum Posts: 173 |
Krisha
I now have tracked down supplies of a good and available screened cable to BS 8436. It is Flexishield LD made by TPWCC. In small quantities it costs about 100 GBPounds (inc VAT) per 100 metre reel of 2.5mm2 standard power wiring cable, smaller cables (1 and 1.5mm2) are available and are cheaper. They also supply 4 and 6 mm2 cables for high current applications.
Note that the current ratings of Flexishield are higher than for standard PVC cables, so smaller sized cables may often be used or standard ("ring circuit" value) 30A circuit breakers used with radials rather than limiting them to 20A as you have to do with standard PVC twin & earth cable.
standard 1mm2 - 14A; 1.5 - 18A; 2.5 - 24A (at 30 deg C)
Flexishield 1mm2 - 19A; 1.5 - 24A; 2.5 - 33A (at 30 deg C)
In a folded ring, such as you are thinking of, it seems as if 1.5mm2 Flexishield will meet the BS/IET regulations with a 30A circuit breaker. Whether the saving on cable costs would be worth it when compared with the total job costs ould have to be thought about - but the smaller cables would also be easier to install.
It is actually cheaper than the fireproof alarm screened cables (e.g. FP200 and FW950) and it is the only screened cable fully certified for general residential use. The others cables are OK but a fussy inspector could require that you show evidence that they actually are suitable (crazy, as they are actually better!), so for new installations it will be best to use BS 8436 cables in homes.
3 and 4 core versions are available for multiway switching. It is distributed by the Cleveland Cable Company Ltd, a very large distributor who ony usually supply the electrical trade but will sell at their trade counter for relatively unusual cable types like this. They they sell large quantities of these particular cables to shop-fitting electrical companies.
Cleveland Cable are based in Nottingham and have branches in Glasgow, Newcastle, Middlesborough, Newcastle, Warrington, Bristol, Milton Keynes and Belvedere, Kent. www.clevelandcable.com
I hope this is helpful. Thanks for pushing me to get to the bottom of this important practical issue.
Alasdair
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Post Time: 22/02/2008 00:13:43 |
krishna
Total Forum Posts: 9 |
Thanks Alasdair! Seeing electrician tomorrow so will discuss. Actually I found the Flexishield stuff before and put costings in my last posting, but I guess you didn't see that. Interesting that you can use smaller cable for the wiring. I'll put that to the electrician too. There is also Pirelli Earthshield and Nexans Alsecure, both BS8436, but not come across a supplier for those.
Krishna |
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Post Time: 19/03/2008 14:25:32 |
tmeehan
Total Forum Posts: 5 |
I am also re-wiring and really appreciate all the info on the site. I had a couple of questions re lighting:
1. My children will have sleeping platforms which currently show halogen downlighters underneath them. I plan to use shielded wiring through out the house. I spoke to my electrician about having a single transformer away from the platform but he said as I have halogens and a traditional pendant on the same circuit I couldn’t have a separate transformer? Is there some way I can shield them from the EMFs off the lights beneath them or do I need to have 2 circuits (and more 2 way dimmer switches and wiring)?
2. Would the shielding paint work if I painted it on the ‘floor’ of the platform / is it necessary? I do intend to paint it on the external walls in their rooms so maybe there will be too much bounce if it is inside as well
3. Is there any affect anyway if the lights are off?
4. They currently have metal cloths that are earthed under their sheets but this requires a plug near their bed – is it better to have no plug or better to be ‘earthed’ in this way
5. They will require a reading light and it is safer for it to be a wall light – assuming I use shielded cable and the light isn’t metal and is placed 70cm above their heads will they be protected. Presumably there is only an effect when the light is on.
6. They also currently have a 2-way dimmer switches by their heads to allow turned either off without having to climb up and down. What can I do to minimise the risk and is there one when the lights are off (which they will be mainly when they are up there)
7. Finally I have heard of someone having a switch in each bedroom that switches off all the plugs in the room - does this make sense. Similarly I know that you can have an 'earth' switch by the front door that all non essential plugs are wired to to turn them all off as you leave to save environmental damage - any thoughts on this.
Thank you for your input
Tara
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Post Time: 19/03/2008 17:40:16 |
alasdairP
Total Forum Posts: 173 |
1. This isn't clear to me, sorry. Firstly, halogen lights run very hot and are not normally used in semi-enclosed spaces, especially with wooden(?) sleeping platforms. Maybe they are mounted on arms that hold them away from underneath the bed base? Whar is underneath the sleeping platform? Is it a desk/work area? The latest fitted halogens have electronic power supplies rather than transformers. I think I need more explanation before I can help here. I would be tempted to go with LED lighting - quite expensive, still, to buy, but lasts almost for ever and are very, very, efficient and low in EMFs. It runs of the mains ok now. Also, bright light, especially blue-white, which halogens emit, is not god for anyone, especially children, after about 9pm at night (it affects the pineal gland sythesis of melatonin for the whole night if the eye is stimulated by bright light late in the evening see -
www.leukaemiaconference.org/programme/speakers/day3-foster.pdf ).
2. The shielding paint only works for electric fields, so I wouldn't recommend it here. The transformers give of mainly magnetic fields.
3. If their lights are properly off, then there are no fields. However, some halogen lights with built-in tranformers and a built-in switch, actually switch off the low-voltage side and leave the transformer connected to the mains at all times. You would need to check what the units were like.
4. I would contunue with the metal cloths and the earthing wire. I think that is a good idea. The wire can be long to the nearest socket - you don't need the socket to be right next to the bed.
5. I would go for a wall-light that can take an LED fitting bulb. Definitely not a halogen nor a CFL (compact fluourescent) lamp. Ask if you want me too look about for what is now available.
6. Do they really need dimmer switches? They do give off more emfs than regular ones. Dual ordinary off-off switches, one for bed light and other for the under-light should be fine.
I would have thought one dimmer switch by the door for adults to use and set and then just straight on-off switches for their actual bed/reading lights would be much better. If they need any light at night in the room (not good unless very dim like a dark but moonlight night), then the best things to use are the orange glowing 13A plugtop lights that look just like an ordinary mains plug but glow when plugged in. They are very effective when you wake up in the middle of the night and then seem quite bright.
7. I don't think a demand switch should be necessary.
I don't know about the earth switch, but it sounds complicated to organise. I think it is just better to turn off unessential things when you are not using them. Otherwise surely it make life very complicated re what plugs in where?
Alasdair
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Post Time: 20/03/2008 09:36:46 |
tmeehan
Total Forum Posts: 5 |
Thank you Alisdair. FYI the sleeping platform is a proper mezzanine above the door so like a normal ceiling and not enclosed. Have spoken with the architect who also recommends LEDs throughout. Don’t they also need transformers which would give off EMFs and would it therefore be best to use one for all of them in the room to one side (would rather not if poss)?
I will look at LED wall lights (is the transformer not an issue here?) are they much better than incandescent wall lights (heat aside)?
Tara
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Post Time: 25/03/2008 20:02:26 |
tmeehan
Total Forum Posts: 5 |
Dear Alasdair,
A couple of further questions...
Your note about the shielding paint concerned me as we had someone to measure the EMFs in the house before we bought it and he located in the next door house what he thought what must be a base for a cordless phone by the wall in one of the bedrooms. I was planning to paint carbon paint on all the side walls in the bedrooms to ameliorate this problem (and hopefully deal with any new phone masts outside etc). Are these electric fields and therefore will be absorbed or do I need to do something else to shield the bedrooms
Also one of the bedrooms is next to a television room and at the level where the bed is there will be a number of plugs, plus TV and BT sockets. What can I do to prevent EMF going through the wall please.
Can you recommend a good torroidal transformer for halogens and a good brand for dimmers too. I spoke with my builder who commented that with a single transformer you need much thicker cable to each light (might this increase the EMFs again?) He wonders what you think from an EMF perspective, of using mains voltage halogens instead.
I do plan to use LEDs where I can and reduce the number of dimmers also, but may as well use the best ones when I do.
Thank you for replies to both my comments in advance
Tara
Tara
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Post Time: 10/04/2008 18:18:06 |
alasdairP
Total Forum Posts: 173 |
Sorry about the delay is responding.
1/. Shielding paint should be OK re the phone unit.
2/. It will also work, if earthed, to keep fields from the plugs down in the bedroom. However, it would be best to locate the TV not close to the bed wall as the highest fields come out of the back of televisions. It would be best to get a TFT or LCD flat television as these produce hardly any magnetic fields compared to a traditional TV - but still don't mount in on the party wall, but stand it on a table at least 15 cm away from the wall.
3/. The electrician is correct re. the toroidal transformer and thicker wire but the thickness of the wire does not increase the magnetic fields. Mains-voltage halogens would be OK but I think they are on the list to be withdrawn so would not be a good long-term option. I do not have any specific transformers to recommend. Probably low voltage halogens with electronic 'transformers' would be best - but you need to check that they can be used with dimmers as some are not able to be dimmed.
Alasdair |
