cable size help needed please

T

taylor467

Hi everyone. Im new here so sorry if this is in the wrong section. I have just set up on my own and been asked by a customer to install some socket outlets, lighting and electric heaters in a stable. Im goin to view the job on tuesday so ill know more about it then. But when speaking to the guy he said the stables is 250m awayfrom the house. he said there is already ducting in place with man holes to take the cable.

My question is it has been ages since i did any cable calcs (last time was at college) so could any of you kind sparks out there refresh my memory a bit with the calcs please
 
You or the client, needs to define the anticipated maximum load, without this you may as well be pxssing in the wind
 
What qualifications do you have?

Calculate your load, apply derating according to the tables in the regs to determine suitable cable size.
 
taylor, it's probably a good idea to buy this book ASAP...
Electrical Installation Design Guide: Calculations for Electricians and Designers (2nd Edition) - IET Electrical

:-)




edit....

Looks like Marv needs to change his name! :uhoh2:
 
Hi marvo, I uave my 17th, nvq level 3 and so on(to be honest I cannot remember all the numbers but I am a qualifed electrician with my jib gold card) and if putting in a sub main for the stables wouldnt the max demand be 54amps 32a ring 16a radial for heater and 6a for lighting
 
taylor467 said:
Hi marvo, I uave my 17th, nvq level 3 and so on(to be honest I cannot remember all the numbers but I am a qualifed electrician with my jib gold card) and if putting in a sub main for the stables wouldnt the max demand be 54amps 32a ring 16a radial for heater and 6a for lighting
Click to expand...

With that sort of design current and length of cable you are looking at a minimum of a 70mm cable. What about applying some diversity to your loadings.
 
I have serioisly fogotten to do all this stif, ive just bought the book u recomended. How do apply diversity. God I sould go back to school
 
Open your OSG bud, it's all in there, black and white. No calcs required to apply diversity :) I'd also start by reducing your socket circuit to a 20A radial, that'll help a little too.

As for your design load, you're gonna need to apply diversity! lol, either that or get the ads up in the local rag for a cable pulling gang :D
 
taylor467 said:
Hi everyone. Im new here so sorry if this is in the wrong section. I have just set up on my own and been asked by a customer to install some socket outlets, lighting and electric heaters in a stable. Im goin to view the job on tuesday so ill know more about it then. But when speaking to the guy he said the stables is 250m awayfrom the house. he said there is already ducting in place with man holes to take the cable.

My question is it has been ages since i did any cable calcs (last time was at college) so could any of you kind sparks out there refresh my memory a bit with the calcs please
Click to expand...

Good start in using a forum as your design team!
 
Why the diy section? Im not jo bloggs whos knows nothing. I am an electrician. Thanks to everyone for the advice. Ill have to get the regs book and osg out I guess. Thanks again
 
Hi Taylor

Ignore some people on here are quite raw as one poster said calculate maximum load then apply diversity or calculate amps of all appliances to work out actual load then you will need to calculate voltage drop and select relevant cable
 
Last edited:
taylor467 said:
Why the diy section? Im not jo bloggs whos knows nothing. I am an electrician. Thanks to everyone for the advice. Ill have to get the regs book and osg out I guess. Thanks again
Click to expand...

To get the best out of the forum its a good idea to offer up your thoughts in more detail and then ask for comments!
 
sajeel said:
16mm 3 core as a suggestion.
Click to expand...

Assuming a 240V supply, unless all loads within the stables are specifically designed to work at lower voltages (which I very much doubt) the Ib would have to be less than 8.5A to allow a 16mm SWA to provide enough voltage to allow the lighting circuit within the stable to comply with section 525. I would think that with the heaters, the socket circuit and lighting needed this is going to be highly unachievable! Think bigger :)
 
Even without calcs I could safely say that Sintra hit the nail on the head with a minimum cable size of 70mm, I would say even with diversity applied. It's very much the rating of the heaters in this situation that will determine whether or not a 95mm cable size would be needed.
 
D Skelton said:
Even without calcs I could safely say that Sintra hit the nail on the head with a minimum cable size of 70mm, I would say even with diversity applied. It's very much the rating of the heaters in this situation that will determine whether or not a 95mm cable size would be needed.
Click to expand...

250 metres of 70mm.... Thats going to be one expensive heater. 5 grand..?!:devilish:
 
No one has mentiond the volt drop here as a 250m run will incur a significent volt drop!
 
I would think that once the OP has done the calcs, the estimate he submits will be thrown in the bin far quicker than the time it has taken me to write this reply......
 
hi everyone. thanks again for all the advice. after viewing the job this morning. it is a 200m run on a TT system. the stable s actually only having lighting and sockets. there is only going to be 3 doubles so a 16a radial will do for that. and for the lighting there are going to be 8 led floods at 8w each giving 64w in total

64w would give .28amps right?
plus the 16amp for the radial
giving me a design current of 16.28amps

is this correct?

im thinking a 25mm 2 core armoured from the house to the stables and then 25mm earth on a earth rod at the stables

could any of you tell me if im right, or close. or have i got everything wrong. i think i worked the volt drop out at 7.7a
 
by using a little diversity, reduce your design current to give a VD of 3%, this will comply for the lighting.

edit: just done a quick calc. and i get a current capacity of 19.5A to give a VD of 6.9V.
 
telectrix said:
by using a little diversity, reduce your design current to give a VD of 3%, this will comply for the lighting.

edit: just done a quick calc. and i get a current capacity of 19.5A to give a VD of 6.9V.
Click to expand...

Thanks for your reply telectrix, can you please tell me how you got 19.5. And 6.9. I also forgot to mention there will be a supply for a alarm as well, prob another 3 or 5 amp. Do you think 25mm swa would be enough, or would 35mm be better?
 

Similar threads

S
  • Question Question
Cable calcs for right size cable
Replies
15
Views
446
DefyG
D
Charlie_Don't_Surf
Steel conduit maximum capacity for 90 degree thermosetting cables
Replies
1
Views
417
westward10
westward10

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Green 2 Go Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses Heating 2 Go Electrician Workwear Supplier
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Advert

YOUR Unread Posts

Daily, weekly or monthly email

Receive a daily, weekly, or monthly email containing a digest of new and recently updated threads.

Thread Information

Title
cable size help needed please
Prefix
N/A
Forum
Electrical Wiring, Theories and Regulations
Start date
Last reply date
Replies
35

Thread Tags

Tags Tags
cable cable size help needed please size

Advert

Thread statistics

Created
taylor467,
Last reply from
gaz101,
Replies
35
Views
3,329

Advert

TrueNAS JBOD Storage Server

Tilers | UK Tiling Forum | Tilers Forums | Find a Tiler
UK Tiling Forum by Tilers Forums UK
Plumbers Forums | Plumbing Advice | Gas Forum
Outside Play
Back
Top