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Anonymous Poster #1

Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/15/2013 12:34 PM

Hi Users

Just wondering what should be the main considerations when using an existing feeder (fused switch) as an emergency incoming supply (from a generator) on an existing distribution board, providing the following assumptions are made:

- the existing 200A fused switch and cabling to it is adequately sized

- the load to be supported doesn't exceed the fused switch size

- we can accept a short outage between loss of mains and availability of emergency supply

- we will have an interlock arrangement preventing mains and generator supply for simultaneously supplying the distribution board

- a phase rotation instrument will be installed to ensure correct phase orientation

Any help would be greatly appreciated so that I ensure the designers are kept on their toes!

Thanks.
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ramvinod
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#1

Re: Using existing outgoing feeder as an incomer (415v Distribution Board)

08/15/2013 1:10 PM

Yes it can be done.However the Generator rated current to be less than 200 A( fuse switch rating)

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 Ramesh,Freelance Electrical/automation Consultant
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lyn
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#2

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/15/2013 2:38 PM

Are you worried about code requirements and insurance coverage in the event that the building burns down?
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wareagle
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#3

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/15/2013 8:03 PM

quote ramvinod "Yes it can be done. However the Generator rated current to be less than 200 A( fuse switch rating)"

Why would you need that requirement. The 200 amp fuse would limit the load on the generator. Suppose you have a large motor that requires175 amps FLA. The starting amps may be 3 times the FLA and the generator might not be able to supply the LRA. Do you have a reason for the limitation?
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ramvinod
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#4
In reply to #3

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/15/2013 11:48 PM

It is only precautionary advice to restrict the load to 200 A.There is no other reason.

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 Ramesh,Freelance Electrical/automation Consultant
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Pattabhiraman
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Join Date: May 2013
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#5

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/16/2013 12:02 AM

The following should also be provided a) Earth fault protection for the D.G source. b) The changeover arrangement shall be of four pole type. c) overload protection for the D.G to be provided.
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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#6

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/16/2013 3:11 AM

d) in order to protect the cable, the 200A fused switch is presently at the wrong end of it. Presumably this will be corrected during the re-routing exercise?

As in all things, local electricity regulations apply. In the UK, consult British Standard 7671.

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1capybara
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#7

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/18/2013 7:19 AM

...if this is a USA installation, it may qualify under the tap rule, NEC 240.21

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Gene2013
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#8
In reply to #7

Re: Using Existing Outgoing Feeder as an Incomer (415v Distribution Board)

08/18/2013 8:25 AM

It's for a UK installation....thanks
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Users who posted comments:

1capybara (1); Gene2013 (1); lyn (1); Pattabhiraman (1); PWSlack (1); ramvinod (2); wareagle (1)

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