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Post Time: 25/02/2009 21:31:41 |
elle66
Total Forum Posts: 15 |
Hi Alasdair, I'm going back to the electricians with my exact specifications and I'd just like to run it by you first to make sure I'm on the right track.
We've decided to go for the recommendations in your House Electrical Installations and EMF's document (Page 17, section 3.3 - from the SAGE report). In addition to this we'll also make sure it's a metal consumer unit (which is located high up on the garage wall underneath my child's bedroom - should I move this towards the bottom of the wall?). And regards the wiring, am I right in thinking that screened cabling is INSTEAD OF metal conduits?
I think these recommendations mean that it will be less complicated to do, i.e. cables can be run anywhere, not just around the edges of the rooms, the distance from the bed positions won't matter and the lighting wiring that you and neuroki were discussing earlier won't be applicable?
I also have some queries with regards to lighting. My kid's bedrooms are above garage/kitchen where I plan to install 2 spotlight ceiling bars in each. Each bar contains 4 GU10 halogen lights which I will substitute with Enviro-Light LED GU10 3 Watt 220-240V. Will this have the desired effect of cutting out the magnetic emissions in the bedrooms above? Also is it ok to have LED wall lights wired either side/above my own bed?
Look forward to hearing from you.
Many thanks, Elle |
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Post Time: 02/03/2009 17:38:53 |
alasdairP
Total Forum Posts: 173 |
Elle, sorry for the delay in responding. I have been away.
I assume that you are planning to use screened cable as you say the wires can run any-which-way. Prysmian FP200 Gold seems about the best value and is acceptable for domestic wiring. Screened cable does not require metal conduit.
The lights all seem OK. Be wary of CFLs. LEDs are good, but are not usually very bright. Some real halogens require heat-proof fittings - check that the GU10 fittings are OK for hot halogen bulbs in case you want to fit them later in place of LEDs. None should be a problem with magnetic fields if you use mains-voltage halogen lamps (rather than 12/24 volt).
Alasdair
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Post Time: 05/03/2009 11:48:33 |
elle66
Total Forum Posts: 15 |
Thanks very much for your reply Alasdair, really helpful. Just a couple more questions if that's okay.
Is it advisable to move the consumer box down the wall in order to position it away from my daughter's bedroom?
Now been advised to have a burglar alarm. Is it okay to have one with PIR's(corner of rooms, on landings, front & back doors and flat roof)?
Many thanks
Elle
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Post Time: 10/03/2009 11:08:13 |
alasdairP
Total Forum Posts: 173 |
1/. Yes, probably, but the fields also come from the wires so if they all mostly trail down the wall from above then there is not much advantage it moving the consumer unit too low. It is recommended that it is at a height where you can easily reset the MCBs (fuses) without having to stand on anything, so you don't want it up close to the ceiling.
2/. Usually no problem at all. Do get the normal PIR type and not the microwave motion detectors. Ultrasonic are OK but not good if you have pets. Again, like for the consumer unit, site the control box carefully as they normally contain a transformer that is not designed for low EMF. 1.5 metres from where anyone sleeps should be enough distance.
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Post Time: 10/03/2009 11:49:22 |
elle66
Total Forum Posts: 15 |
Thanks very much Alasdair. Thanks too for your updated version of the House Wiring doc, that was invaluable because it prompted me to check that the electricians were intending using the Prysmian FP200 Gold cable. Just discovered that they weren't and we're starting the work tomorrow so they've now gone away to re-order.
Thank you for all your advice in this matter, I really appreciate it.
Elle |
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Post Time: 10/03/2009 12:28:40 |
elle66
Total Forum Posts: 15 |
Hi Alasdair,
Sorry....just when you thought I'd gone away!
Electrical Company have just come back to me and told me that the cable they're going to use is FP200 made by Ventcross Limited (to BS7629-1 1997). Is this acceptable? I have told them that I want the Prysmian Gold but the manager is out of the office so I'm not able to check right now what, if anything, the problem is in getting this or whether they simply prefer the Ventcross.
Look forward to hearing from you.
Elle
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Post Time: 10/03/2009 12:49:43 |
alasdairP
Total Forum Posts: 173 |
I can find no trace of Ventcross Ltd as a manufacturer, distributor or retailer of anything electrical in the UK or elsewhere. I suggest you ask them for a specification sheet for the cable or company details so that you can get the datasheet for yourself.
Some FP200 cables (like Prysmian FP200 Gold) have a proper metal aluminium screening foil. However some cheaper FP200 just have an aluminised fabric fireproof inner sheath and this is nowhere near as good at stopping electric fields (FP200 is primarily a fire-retardant cable and is not INTENDED to be an electric field screening cable as such, so this cheaper form of inner layer is actually permitted under the BS7679-1 1997 rules). I have no idea what the inside layers are like of cable they wish to use.
So, maybe ask them for a short piece and look to see it it has real aluminium metal foil inside around the wire bundle or just a treated plastic foil layer.
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Post Time: 10/03/2009 16:34:21 |
elle66
Total Forum Posts: 15 |
Thanks again Alasdair. Have told them I want the Prysmian but had no response, hope they're trying to source it.
Elle |
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Post Time: 10/03/2009 22:43:46 |
alasdairP
Total Forum Posts: 173 |
Prysmian isn't essential. There are other makes of FP200 with solid metal foil screening. The cable they want to use may be quite OK. Ask them for a sample piece and take it part and see if the screen is metal (which tears easily like kitchen foil) or just metalised plastic (which is much tougher and difficult to tear).
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Post Time: 11/03/2009 14:48:12 |
elle66
Total Forum Posts: 15 |
Hi Alasdair, the cabling they were going to use didn't meet the requirements so thanks for alerting me to this.
They're now going to use one made by Nexans (www.nexans.com). It is called ALSECURE BS8436 NXS. They've assured me that it is the same as the Prysmian but cheaper. They've given me the spec sheet and it does say that it has a bonded aluminium screen so I'm hoping that it will be fine. They haven't ordered it yet until I give them the go ahead. If you were able to have a quick look at the website, I'd be extremely grateful.
Many thanks
Elle |
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Post Time: 11/03/2009 22:50:01 |
alasdairP
Total Forum Posts: 173 |
Gosh, that data sheet took some finding. Yes, it looks like an excellent cable and has a solid aluminium sheath. For other readers, the data sheet is available here:
www.nexans.com/eservice/UK-en_GB/navigate_120396/ALSECURE_BS8436_NXS_2_3_4_core_1_5_6mm.html#top
(you will need to make sure the whole link is together and paste it into your browser. Sorry, but direct hyperlinks do not work from this forum.)
I am pleased you are almost there! Actually, your questions have help clarify this complex issue. I expect other readers will find them Q&A helpful, too. Good luck and best wishes for your re-wiring!
Alasdair
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Post Time: 12/03/2009 09:45:34 |
elle66
Total Forum Posts: 15 |
Many thanks Alasdair, I can finally sleep easily knowing that this has been taken care of (just got to worry about the potential asbestos in the artex now!)
Has been a learning experience for the electricians too. Although they're very good and are familiar with routing wires away from bedheads, radial wiring and using metal conduits for unscreened cables in the loft, they weren't aware of the differences between the FP200 cables.
They put me in touch with an electrically sensitive guy that they'd done a recent rewire for but I didn't want to put the cat among the pigeons by asking him what cabling they'd used! I did point him in the direction of Powerwatch though.
Once again, all my thanks for your extensive advice.
Elle |
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Post Time: 17/03/2009 00:08:31 |
alasdairP
Total Forum Posts: 173 |
I am please we have been helpful. I wouldn't worry about potential asbestos in artex - just keep it well covered with paint and it will stay there out of your way.
A.
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Post Time: 13/05/2009 08:32:26 |
elle66
Total Forum Posts: 15 |
Hi Alasdair, hopefully a last query re siting of burglar alarm control box. It's less than the 1.5m away from bed areas that you previously recommended. It's in the garage below my daughter's bedroom (exactly below her bed). It measures 120cm up to the ceiling and then there is a concrete ceiling in between. It is encased in a metal box and the wires running up (very low voltage I've been told) are in plastic trunking. It's not easy to move it further down wall because of electrical wiring running directly underneath so obviously electricians are keen to leave where it is. If, however, you think it's advisable, I will insist. Am I right in thinking that the box on the outside wall doesn't present a problem (again, this is probably closer than 1.5m away from two bedrooms). Look forward to hearing from you. Many thanks, Elle. |
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Post Time: 29/05/2009 13:56:20 |
alasdairP
Total Forum Posts: 173 |
Hi Elle, sorry about the delay. The box at that distance should be absolutely fine. The main magnetic fields from the box are likely to be from a small internal transformer and hose fields fall off very quickly with distance - approx. inversely with the cube of the distance. e.g. the field at 3 metres is about 1/27th of the field at one metre and the field at 1.2 metres is 1/27th the field at 0.4 metres.
A. |
