 | Home > Off Topic > one for the sparkies... |
 
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6300   
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so I wondering if I should try and get away with a 6mm T&E over a 10mm T&E.
fitting new cooker rated at 14.8kW but I suspect that is full tilt with no diversity. cooker installation says 46A MCB but I'm thinking of going with 40A and a 6mm cable as I don't envisage every having everything going full whack all at the same time.? thoughts please  |
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18th Dec 2023 7:02pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6300
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lohr500 - the cost might not be significant but the pain in the rear is when it comes to installing.
I'm fully appreciate why you've responded as you have but I'm inclined to think the manufacturers suggestion is a 'cover ones rear' approach. As noted I can't imagine for one second I'll have two ovens, a grill and all 5 or 6 hobs going all at once and all on max so I don't really see the point of catering for that scenario and hence the question. in the word of electrics / design it is quite normal to apply diversity - and thats effectively what I'm doing (I think  ).
valued feedback all the same.  |
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18th Dec 2023 7:28pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6093  
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Go with the higher rating. As a sparky myself (albiet more data/CCTV/door entry stuff, but also 18th and part P certified) go with the bigger size..
"you never know" Quickly looking at TLC... for 10m of 6mm T&E or 10mm T&E...  Click image to enlarge Not much in it.. |
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18th Dec 2023 7:32pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6093
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Diversity usually applies to a whole building, as in, not all of the lights and heaters are on at the same time.
An oven? not sure, but it wouldn't take much say on a christmas day to have everything going at once. |
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18th Dec 2023 7:34pm |
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| 300TDi CSW Phil Member Since: 03 Apr 2016 Location: Bracknell Posts: 750 
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Domestic ovens are the only thing in a house where diversity is applied.
To size the cable and breaker take 10A as a given and then 30% of the rest of the rated max. 1995 300 Tdi Epsom Green - It's a keeper. Wide Track Sankey- In bits- Gone to a new home M0XQS |
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18th Dec 2023 8:44pm |
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| windy81 Member Since: 14 Mar 2018 Location: North Wales Posts: 311  
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Size the MCB with the cable rating.
The MCB/RCBO is to protect the cable and not the appliance so if you want to use 6mm with a 40a MCB that's fine, but don't be surprised if it trips if you have the oven on full tilt. |
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19th Dec 2023 2:32pm |
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| Procta Member Since: 03 Dec 2016 Location: Sunderland Posts: 5183
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When me and my dad did the wash house hot water system, we used the heater system off a electric shower, I bought the thicker wire for it, and the stated MCB, just so there was no foul ups. Also when we added more sockets into the wash house we bumped the MCB to next size, even though we wont have all the sockets going at once etc. Defender TD5 90 ---/--- Peugeot 306 HDI hatch back
Success is 90% Inspiration and 4 minutes Preparation # you can make it! |
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19th Dec 2023 3:19pm |
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| Co1 Member Since: 19 Aug 2018 Location: North Yorkshire Posts: 3681 
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What’s the length of the cable run? Send me the details and I’ll work it out for you in the morning. You’ve also got volt drop to consider if the length is considerable, so while 6mm may be ok for the load with diversity applied, it might be no good with volt drop.
Procta: bumping your MCB to the next size because you added more sockets isn’t a good idea. The MCB is there to protect the cable, not the sockets or appliances. You’ve actually increased the risk of fire by doing that so I would recommend installing and correctly rated MCB. |
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19th Dec 2023 7:04pm |
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| Screbble Member Since: 26 Apr 2015 Location: Lancashire Posts: 2106 
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19th Dec 2023 7:16pm |
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| Procta Member Since: 03 Dec 2016 Location: Sunderland Posts: 5183
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yeah, you are supposed to do a ring main, like a return feed if am right? not sure how me and my dad will do that, where our end socket is, Which is outside one at the front of the house. Defender TD5 90 ---/--- Peugeot 306 HDI hatch back Success is 90% Inspiration and 4 minutes Preparation # you can make it! |
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19th Dec 2023 7:35pm |
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| Screbble Member Since: 26 Apr 2015 Location: Lancashire Posts: 2106
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Procta, you should get that wiring checked by a spark as just reading it it makes me concerned. As said above you need the MCB to protect the cable otherwise it’s dangerous. You can have a radial instead of a ring but again you’ll need an appropriately rated (lower) MCB. You also need to ensure your earthing is spot on, and I’m not sure how you’d do that without an earth loop impedance test. Better safe than sorry 👍
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19th Dec 2023 7:43pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6300
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thank you guys.
I was up against it have bought a drum of 10mm...... but reading some of the posts I'm very inclined to swap it out for 6mm 
we're just perhaps 9m for the fuse board - I'm allowing another 1.5m for the 'fly lead' from DP switch to the over itself - so no major volt drops to be concerned about. from memory (which isn't the best) I'm expecting to break at least the odd one or two plastic surface patresses while terminating the cable into the switch and hence why I'm keen to go with the smaller cable? |
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20th Dec 2023 9:28am |
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| Co1 Member Since: 19 Aug 2018 Location: North Yorkshire Posts: 3681
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Full load at 14.8 kw gives 64.35A max demand. To get it down to a 46A MCB means diversity of 70% ish. Is that reasonable? Volt drop on that length will be 4.09V using 6mm so absolutely fine (max allowable of 11.5V).
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20th Dec 2023 10:21am |
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| Procta Member Since: 03 Dec 2016 Location: Sunderland Posts: 5183
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i will look at MCB again, we still have the old one about anyway, We are looking at getting a compressor next year, which is on a trip system at the socket end, i fitted four of these, two for outside and two in side, one for the compressor and the other was the one they always used for extensions. My dad has fitted a little switch box thing with a light on, which you are supposed to do, every so many?? which because they had a freezer in there, a while ago before me and my dad decided to kit things out. ( just to give him something to do, as he has retired) Defender TD5 90 ---/--- Peugeot 306 HDI hatch back
Success is 90% Inspiration and 4 minutes Preparation # you can make it! |
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23rd Dec 2023 2:13am |
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