Cable Ducting


Postby Rhacuno » Fri Jun 08, 2007 12:55 pm

I'm installing a new bathroom and kitchen (sort of Granny flat) and want to install a new, separate, consumer unit. I need to run the mains supply up from the garage (where the meter is) and across the back of my existing utility room. I'll probably have to get an electrician in to do the actual cabling but I'm currently installing the bathroom and and am stuck with two questions:
A) Is there a maximum distance between the existing meter and the new consumer unit?
B) what type and size of ducting should I allow for?
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Postby sparx » Sat Jun 09, 2007 8:15 pm

Hi,
I'm glad your getting a sparkie in as it would be illegal to do yourself!
He will need to put in a 'tail-splitter' Henley block with tails to a local switch-fuse. Then no limit to distance to new consumer unit, the cable size used will be dependant upon length X current expected to be used (max).
So to make the judgement list what equipment is going in kitchen with
loadings in either Amps or Watts, plus say 5A. for lights/fans etc.
E.G. cooker, water heater, kettle, microwave, toaster, fridge/freezer.
Say loadind allowing for some diversity of use could be 45A/ 9.5 kW.
Therefore if we assume cable distance of 20Metres max, then if run in wire armoured outdoor cable then 6mm would just be inside limit of volt drop allowed for system allowing some for final circuits.
However if using tw/e pvc cable in conduit/trunking you would need to go up to 10mm cable, the physical sizes you can see in local DIY store,
regards SPARX
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Postby Rhacuno » Mon Jun 11, 2007 10:09 am

Thanks, Sparx. It's about a 20m run, so I'll check on the all the appliances as you say to find the max. load. Does it have to be armoured outdoor cable even if it's all run indoors?
Rhacuno
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Postby sparx » Mon Jun 11, 2007 4:10 pm

Hi as per my last sentence of original post, if all inside then twin&Earth OK and can be surface clipped thro' garage, also note it will probably need 10mm2 for load/volt-drop,
regards SPARX
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Postby Rhacuno » Sat Jun 16, 2007 8:28 pm

Sparx, it looks like this little project is growing up fast. We now want to add a shower unit (9.5KW), washing machine and dryer. My estimate now takes the total load it up to around 25KW (if all appliances are running at the same time). Will the 10mm cable to the new consumer unit you mentioned before still be sufficient?
thanks Rhacuno.
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Postby sparx » Sat Jun 16, 2007 10:22 pm

Hi agn. Stick with 10mm2 on 63 A mcb/60A fuse as 25 kW is over 100 A so diversity must apply as otherwise your house would trip off normally since the largest house supply only has 100A max fuse!
It's unlikely 'granny' would take a shower whilst doing toast, making tea, washing & drying clothes at the same time, multi-tasking or what!!!!
Must you have such a large shower? there is very little real difference between 9.5 & 7.2kW items & cable size/cost, volt drop etc less,
regards B.W. SPARX
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Postby Rhacuno » Fri Jun 22, 2007 9:14 am

Thanks Sparx. That's fine, I've put in some ducting to be able to handle the 10mm2 cabling. Just ned to find an electrician now!
On the shower question I guess I just thought a 9.5Kw model would be that much more robust than the the smaller ones - and she is a large granny!
Rgds Rhacuno
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