Which mains cable?


Postby Masterpop » Sat Dec 12, 2009 10:37 am

Hi,
We're in the process of buying an old house which needs a complete electrical re-wire since the current wiring dates back to the 1970... if not earlier!

I plan to use the mains power cables to run my home network, using ethernet over mains, so i'll be streaming music/video as well as data over the mains cables.

Could someone advise on what the best cables for this is? Ideally, i would prefer something shielded to minimise interferece, i'm thoroughly fed up with these "new builds" type of houses where you can't get telephone reception or decent wireless connection. I'm aware that the standard cable is 6242Y, but is there a better alternative?

Thank you, any advice thoroughly welcomed

I'd like to add that I fully intend on getting a qualified, certified electrician to do it. However, i'd like to be fully informed beforehand.
Masterpop
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Postby ericmark » Sat Dec 12, 2009 2:40 pm

Ali-Tube to BS 8436 Guardian, Earthshield, Flexishield, or Afumex is designed to go into composite walls and does not require RCD protection for the cable and since it is in a earthed tube must be better with EMC.

However it seems this cable is only used on commercial premises and to buy cost more and hard to get part roles.

So although designed for the job it is seldom used. Likely area to area there will be different availability but here in North Wales I tried to buy a short length so that I could fit a RCD socket rather than RCD fused connection unit (FCU) then socket. But I failed to find anyone who would supply short length.

As to using mains cables to make a LAN when you are re-wiring seems pointless better to use dedicated cables. Different if you were not re-wiring but you already have the mass so why not do correct first time.

However do consider how many circuits. All IT equipment has filters and as a result some small earth leakage. The more items put on same RCD the more likely to trip.
Cheap way is just 2 RCD's for everything and this is what I have and it does trip from time to time.
Next is use RCBO's which combine RCD and MCB and allow a separate RCD on each circuit and as a result less likely to trip.
Then you can wire with radials rather than rings and have more circuits so even less likely to trip.
Each stage costs more so you have to decide what you want to pay.
There are even auto re-setting RCD's but at £300 each don't think they will be used in normal house. If my Father dies before my Mother then I would buy as she is in a wheel chair. But not really for normal homes.

Look at Screwfix as easy to find things on the site and look at prices. I am not saying buy from there but be aware of what things cost. It is so easy to get two completely different quotes as the electricians intend to fit different items so yes it is good to have a written down itemised list of what you want.

BTW Kitchens will still need ring mains even if rest of house is on radials as kitchens use so much power.

Also consider not having RCD for fridge supply. (Would have to be Ali-tube) and if not how would you know if it failed. Where all power is split up it is easy for something to trip and you are unaware the power has failed. I have seen intruder alarm and fridge on same circuit as when power fails for alarm battery back-up screams at you so less likely to miss if it trips. However where smoke alarms are used there are some odd rules and you would need to OK with electrician.

I have battery backed stair lights and this lights on power failure so alerts me to failure during day time.
ericmark
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Location: Mold, North Wales.


Postby Masterpop » Mon Dec 14, 2009 12:08 am

hi ericmark,

thank you very much for your post, it is very helpful!

on the question of LAN, perhaps you are right- it might be better to put in some CAT5e cables going to a central hub. I just thought with LAN over mains getting more mainstream (Belin Powerline HD in particular), it would be easier to use the sockets. You would generally have more power sockets than LAN sockets, so you can effectively move your network point around the house. I'm not quite sure how well they work across ring mains/radials... for example, the bedroom might be on a different RCBO compared with the living room (where the router might be)...

Why does wiring with radials cost more? is a higher quality cable more expensive than 2x the length of a cheaper cable?

The Ali-Tube cable does seem to be what I'm after... but as you say it's been hard to get a ballpark cost for it on the net. We'll have to see what the electricians in Kent have to say about it.

thanks again for you reply
Masterpop
Posts: 11
Joined: Thu Dec 10, 2009 6:49 pm


Postby ericmark » Mon Dec 14, 2009 12:20 pm

Main reason why radials cost more is you need more RBCO's very little difference in cable length. Although you can have 32A radials with 4mm 90 deg cable it is hard work and normally all power is with 2.5mm cable and 20A on radials and 32A on rings. So ring for kitchen and radials for rest. Most twin and earth rated at 70 deg C but ali-tube is rated at 90 degs C so it can for same size carry more than standard twin and earth of same size. This does not make any difference for rings but 32A radials can only be done with 4mm 70 deg cable if surface but with ali-tube that little extra allows you to bury them. You could use 6mm but except for MK you may have problems getting two 6mm cables into holes in sockets.

Over simplified a bit see here Google "ericpalmer.fsnet.co.uk/Table4D5.html" for some idea of current not A1 but will give you idea. No longer have access to that page so can't correct.
ericmark
Posts: 1189
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.


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