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18 th Edition questions

• Jonathan Swift

Discuss 18 th Edition questions in the Electrical Forum area at ElectriciansForums.net

J

Jonathan Swift

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Welcome to ElectriciansForums.net - The American Electrical Advice Forum

There are two questions that Ive been unable to locate in the regs book;

1. If the line conductor is 10mm2, the min size of of an associated Surge Protection Device connection conductor is?

2. A 230 V 30 A radial circuit is protected by a BS 3036 device. If the value of earth loop impedance for the circuit is [email protected] (I think means amps?), disconnection under line/earth fault condtion will occur in:

2s, 4s, 5s, 3s?

Thanks

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D

Dustydazzler

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Arms
Found this video about SPDs quite informative, and might cover your question iirc

Andy78

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Not sure on 1 as i'm not at my book.

For 2 you need to use the supplied values to work out the prospective fault current and use the tables in appx 3 to find the answer.

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Dustydazzler

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As for the second question it will be ohms and ohms law

You will need to find the time curve chart for the actual tabulated trio times for 3036 fuses

Wilko

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Hi - take a look at Reg 534.4.10 for SPD conductor sizes .

J

Jonathan Swift

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Not sure on 1 as i'm not at my book.

For 2 you need to use the supplied values to work out the prospective fault current and use the tables in appx 3 to find the answer.
Many thanks, so @ was in fact Ohms and not Amps. 230/2.3 = 100. In tables is 3 seconds. Cheers

J

Jonathan Swift

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I have done, on page 170. But it doesnt correspond to the apparent correct answer on the exam paper...

J

Jonathan Swift

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the exam paper states 4mm, 6mm, 10mm or 2.5mm. With the correct answer apparently being 4mm

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Dustydazzler

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I feel a John Ward moment coming on and wanting to pass 100a through a 3Oa fuse wire to see how long it takes to blow...

I bet it’s a dang sight longer than a few seconds

Andy78

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Many thanks, so @ was in fact Ohms and not Amps. 230/2.3 = 100. In tables is 3 seconds. Cheers
I'll take your word for that as not with my book to see the tables ... but sounds good.
Annoying misprint, but maybe it is to do with a technical error with software not recognised the ohm symbol. What study material are you using ?

J

Jonathan Swift

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Ive used quite a few but these two are from sparky facts online page. Thanks for your help, I'm wondering if the second question is just the wrong answer

Andy78

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Ive used quite a few but these two are from sparky facts online page. Thanks for your help, I'm wondering if the second question is just the wrong answer
Thought it might be that site. It's full of errors and out of date questions and answers. Best avoided.

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