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I have been given this assignment "the drawing below shows the floor plan of a small factory with the electrical symbols. Explain the process of designing the final electrical circuit that supplies all the elements 6 . The total length of the circuit is 25m. Any assumptions you have to make should be indicated" and I have no idea how to do it. If anyone could help I would be greatful

Explain the process of Designing a Final circuit tetete.JPG - EletriciansForums.net
 
I'm a first year apprentice, but this is fairly straightforward. I haven't provided an answer for two reasons:

1. I'm not familiar with regulations in Cyrprus.
2. Doing so wouldn't assist with your learning, so I'm trying to point you in the right direction.

Ask yourself what additional factors are involved in the design of this simple circuit? Are you povided with details of luminaire or is this something you have to decide on? You need to specify cable size and type of breaker - both of which can be determined from available information.
 
I'm a first year apprentice, but this is fairly straightforward. I haven't provided an answer for two reasons:

1. I'm not familiar with regulations in Cyrprus.
2. Doing so wouldn't assist with your learning, so I'm trying to point you in the right direction.

Ask yourself what additional factors are involved in the design of this simple circuit? Are you povided with details of luminaire or is this something you have to decide on? You need to specify cable size and type of breaker - both of which can be determined from available information.
We are learning from the BS7671
I have to write about the overload calculations, voltage drop, shock protection and thermal constrains?
 
You've answered part of it by listing cosiderations which must be taken into account.

You know circuit length and number of points served. Do you know power consumption of luminaires? Have you been given information about containment ,or is this something you would have to determine? I ask as this impact upon thermal constraints.

Overcurrent protection will be determined from total load, cable type, inrush current etc.

So far you have made no attempt at answering the question and have simply provided some basic information in the hope that it will be answered for you. I'll attempt to help, and am certain others will step in, if you want help, but no one is going to provide all the answers as that won't help you to learn.
 
It looks like it's just for the lighting?
You might need to assess the current., and all the other things that @nicebutdim helpfully mentioned.
Can't give you the answer, as there will be many approaches here.
Put down your assumptions, then spec the design to those.
If you get bits wrong, you will have learned something useful.
 
Start with the spec of the lights, work out the total power (or more correctly, current) is needed. Assuming it's LED then it'll be fairly low.
You can now have a stab at picking a cable size - though in practice the answer will almost certainly be "the minimum allowed by the regs" (it's in there, you find it :wink:).
You can then work out volt drop and check that it's within limits (again, it's in the book) - if not, then you'd have to up the cable size, find another way of improving things, or decide whether the excess is an acceptable deviation from the standard.
Pick an upstream overcurrent protection type and rating, work out if it's compatible with the fault impedance. Consider the characteristics of the loads when selecting the OCP - for example, if you had a big space with loads of flouro tubes, there's scope for significant inrush current. Most types of light have some sort of inrush - some more than others.
You'll also have to consider the CCC of the cable taking into account the installation method.

If necessary, you may need to iterate. E.g., if you have a larger than typical Ze or Zs, or a long circuit length, you might find that the overall fault impedance isn't acceptable for the OCP you've chosen. So then you need to consider what options there are to fix that.

So there's the steps you should already know - off you go, find the information, and do the calcs. Voila, circuit designed.
 

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