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sarakana
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Max. No. of Three Phase and Single Phase Circuits to be Connected

09/13/2013 1:52 AM

A 100A 3 phase, 400V Distribution board has 44 Nos of 6A 3 phase Outgoing feeders (Including spares). How is this possible? Coming to the load connected, if all the outgoing feeders are fully loaded, will the load not exceed the Incoming feeder (100A) load?

Please give me a solution for this. What is the maximum No. of 3 phase and Single phase feeders be connected to the 100A Distribution load?
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lyn
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#1

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 2:23 AM

Hire a local person who understands the codes and the actual distribution system and the math.

We cannot see it from here.

Maybe a search is in order.
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Tornado
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#2

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 2:31 AM

There is no maximum. It need not be assumed that all connected items will be energized simultaneously. Instead, one considers diversity factors and non-concurrent loads.

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PWSlack
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#3

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 3:30 AM

<...will the load not exceed the Incoming feeder (100A) load?...>

No, because were it to do so, the circuit protective device(s) on the feeder will operate, disconnecting it.

Consider a situation where, say, half those connected circuits are each drawing 1A, and the light switches are all turned off on the remaining circuits. That's called "diversity".

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#4

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 5:25 AM

So how come it has 44? Shouldn't it have 42 or 48?
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kirankk
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#5

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 6:59 AM

hi, your Incoming is 3Phase, 400V and outgoing is 6A single phase (240V)feeders. so, you can connect each phase 14Nos of 6A Feeders. If you connect all the 44 Feeder and energised also load amps will be 80 to 85A only so 100A is OK.
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sarakana
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#6
In reply to #5

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 7:13 AM

Thanks for your reply. Can you brief with loading details how 14 nos single phase feeders can be cannected per phase
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PWSlack
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#7
In reply to #6

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 7:17 AM

One circuit to each breaker terminal.

Is it time to move on yet?

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kirankk
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#8
In reply to #6

Re: Max. No. of three phase and single phase circuits to be connected to 100A Distri

09/13/2013 7:28 AM

This is possible if single phase circuit only. for 3Phase circuits is not correct
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Phys
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#9

Re: Max. No. of Three Phase and Single Phase Circuits to be Connected

09/13/2013 9:02 AM

There are projected loading factors to be considered. For example, while working at an electrical consulting firm, I could design a 20A single phase circuit with up to 6 dual outlet, 20A receptacles on a single 20A breake, or as few as one. The first case is 240A on a 20A breaker, while the second is still 40A, but when is the last time you saw a receptacle with two 20A devices on it? In a church vestibule, 6 was very normal. About the only thing going onto those recepts was the janitor's sweeper. In an office, with all the (40 years ago) adding machines and mimeographs, a few less. Same with a panel. No way are all those circuits running 6A simultaneously. Many are probably spare and most probably have 1A or less on them. Remember the breaker is there to protect the wire, not the equipment. it is much easier to load up with 6A breakers for everything, than to have an assortment of 1A, 2A, 3A, and so on.

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LAA_Lucke
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#13
In reply to #9

Re: Max. No. of Three Phase and Single Phase Circuits to be Connected

09/14/2013 6:09 AM

Correct: Protect the wires from being overloaded and start to burn etc.

The equipment will draw what it needs. therefore, the supply wire gauge is most important, then protect IT from being overloaded. Then the main CB ( here 100A 3ph) is supposed to protect the DB bars etc from overloading and heating up.
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RAMConsult
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#10

Re: Max. No. of Three Phase and Single Phase Circuits to be Connected

09/13/2013 10:18 AM

The answer lies in the local code and/or the AHJ (Authority having Jurisdiction). The diversity factor will be dependent upon where this panel is installed, residence, industrial, hospital, movie theater, etc. Simply looking at the breakers and adding them up won't work.

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dhayanandhan
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#11

Re: Max. No. of Three Phase and Single Phase Circuits to be Connected

09/14/2013 5:17 AM

Dear Mr.saarakana,

The idea is out going feeders summed up load should not exceed the Capacity of the Distribution Board, after careful consideration for de-rating factor etc. 44 Nos. of out going feeders - means, there may be or should be some inter-locking between them.

The Relevent Code will not permit. Pl. let us know wheter inter-locks are there, how many for stand-by.

A thorough study is needed.

DHAYANANDHAN.S
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brich
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#12

Re: Max. No. of Three Phase and Single Phase Circuits to be Connected

09/14/2013 5:24 AM

If ALL your circuits are FULLY LOADED at the SAME time, then you have designed your distribution board/circuits incorrectly.

As mentioned in a previous post by Tornado there is a factor called "diversity", which you seemed to have missed, as I guess you don't understand. I suggest you google "diversity" and look at the British Standards, which explains it exceptional well for a fuller understanding.

Now my question? Is this home work?

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pillay
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#14

Re: Max. No. of Three Phase and Single Phase Circuits to be Connected

09/14/2013 9:18 PM

Too many details to understand , take up a course to become a qualified electrician or leave the details to the trained ones.
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Anonymous Poster (1); brich (1); dhayanandhan (1); kirankk (2); LAA_Lucke (1); lyn (1); Phys (1); pillay (1); PWSlack (2); RAMConsult (1); sarakana (1); Tornado (1)

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