Discuss 3 phase supply in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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jordans

I need to get a 3 phase 400v supply over to a unit with around 32amp per phase.

The total length of the run is 108 meter fro source to consumer unit.
From the consumer unit there is already an existing 4 core 35mm SWA cable running 50 meters
And from the supply side there is a 4 core 20mm SWA cable running 25 meters/

This leaves me with a distance of 33 meters of cable to run between the two end and connect.

If any one can help me with a cable calc and volt drop for this 33 meters or even the whole run, to get the desired 32amps per phase at the consumers end, and also any other information that might help me to do a professional job would be greatly appreciated.

many thanks jordans
 
In your profile it says you are an electrician! So whats the problem? Get your BGB out and have a read

What he said plus with your qualifications, you shouldn't need to ask such a basic question
 
Hi jordans. What value would you use to calculate the VD on 20mm cable?
 
or even 10mm. that's about 20mm O/S diameter.
 
Welcome to the forum jordans....

Heads up as your new .. its customary to show your own calcs and we can guide you if we spot errors, we are not in the habit of doing them for you as this ends up with us getting a barrage of homework questions and people asking us to do their calcs for them as they are not competent to do it themselves.

You say you have done and apprenticeship in Electrical Engineering but this is a bit vague ...was cable calcs part of your learning as would have been if you did a full Electricians course?
 
Yes i understand how this looks guys,
I completed my apprentice in electrical engineering although it was some time ago and since set off travelling the world for four years with no electrical work ( i.e. cable calks)

I just thought id join this form to see what it was like and if anyone can help blow the dust off as i now can't remember how to do so.
 
VD = ( mV/A/m x L x I)/1000. where L is the length in metres, I is the amps, and mV/A/m is in the green, red,yellow books and OSGs.
 
I need to get a 3 phase 400v supply over to a unit with around 32amp per phase.

The total length of the run is 108 meter fro source to consumer unit.
From the consumer unit there is already an existing 4 core 35mm SWA cable running 50 meters
And from the supply side there is a 4 core 20mm SWA cable running 25 meters/

This leaves me with a distance of 33 meters of cable to run between the two end and connect.

If any one can help me with a cable calc and volt drop for this 33 meters or even the whole run, to get the desired 32amps per phase at the consumers end, and also any other information that might help me to do a professional job would be greatly appreciated.

many thanks jordans

3 phase consumer unit are you sure?


New size of cable been made is there?
 
Yes i understand how this looks guys,
I completed my apprentice in electrical engineering although it was some time ago and since set off travelling the world for four years with no electrical work ( i.e. cable calks)

I just thought id join this form to see what it was like and if anyone can help blow the dust off as i now can't remember how to do so.

Its not often Ill promote the short courses to become an Electrician but on this rare occasion it sounds like your the exact type of person with previous electrical knowledge and experience that these courses were designed for so my recommendation is before you step back into the electrical realm you could do with bringing yourself up to date, cable calcs are in the regulation books and it shows you how to do them so Ill assume you don't have these.

As I said we are happy to help those who help themselves but we don't run a free calculation service for those who can't be bothered or just can't do it, if you have no idea how to do the calcs regardless of reasons then you are not competent to undertake any electrical work as signing it off would need this knowledge to ensure the install is designed correctly.

Electrical Engineering can cover a total different section of the industry than what is learnt when training as an Electrician hence I asked what area your Engineering field was you were learning and what you got for passing i.e. HNO HNC etc etc....

We lack so much info about the existing set-up like existing loading, compliance with 17th as adding an addition may mean the whole run would require to be upgraded if it was an option. Your new supply you mention is 3ph 32amp but no mention of what the load is and it characteristics and start up inrush + duration if its applicable.... Im just scraping the top off the iceberg here as many other crucial factors has to be taken into account like nature of the DNO supply whether extra measures are needed to extend the equipotential zone or isolate and rodding.

To simply give you the answer when its clear you a bit out of touch with electrical design would be irresponsible of us hence im recommending taking a booster course or work alongside a competent person and learn as you help but don't try doing this with your existing knowledge as you may create a safety risk to property or life... alternatively walk away and stick to what you are comfortable with but TBH any Electrician carrying out any work would require to have knowledge about cable calcs.
 

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