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# Bit of a cheeky 17th edition question......

Discuss Bit of a cheeky 17th edition question...... in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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#### Shakey

Welcome to ElectriciansForums.net - The American Electrical Advice Forum

Ok, try this

A submain supplying a distribution board is protected by a 30A BS3036 fuse, what is the maximum permissible design value Zs

A) 1.59ohms
B) 2.64ohms
c) 1.09ohms
d) 2.80ohms

E

#### EasyFox

Morning Shakey

Hmmm I haven't got my copy of 17th with me (& havent had a good read) so this is off the top of my head.

I'd go 2.8 ohms as it's a distribution circuit so 5sec disscon time? (assuming cables are installed correctly to not require an rcd)

Go on tell me I'm wrong, should have left the good book in the van.

#### ian.settle1

##### -
Mentor
Arms
Morning Shakey

Hmmm I haven't got my copy of 17th with me (& havent had a good read) so this is off the top of my head.

I'd go 2.8 ohms as it's a distribution circuit so 5sec disscon time? (assuming cables are installed correctly to not require an rcd)

Go on tell me I'm wrong, should have left the good book in the van.
haven't got a copy of 17th yet but i thought all disconection times had been reduced to 0.4 seconds?

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#### Shakey

Well done EasyFox answer is actually 2.64 ohms but not far off

initially threw me this one

Table 41.1 gives disconnection times for 230V TN systems as 0.4S and 411.3.2.2 says table 41.1 should be used for final circuits not exceeding 32A

Table 41.2 is for 0.4S disconnection times (30A is 1.09 which is one of the answers)

Table 41.4 is for 5S disconnection times (30A is 2.64)

Great, thinks me, table 41.2 is 0.4 S, its a 30A fuse so 1.09 is the answer.......

until i read 411.3.2.3 " in a TN system, a disconnection time not exceeding 5 s is permitted for a distribution circuit a circuit not covered by reg 411.3.2.2"

and of course under the definition for a distibution circuit, it says "it is sometimes called a submain"

so it comes under the 5 s table even though it is less than 32A

cheeky bast*\$%s!!!!!!

and 411.3.2.4 allows you to go to 1 s for a TT distribution circuit, instead of the 0.2 s in table 41.1

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#### EasyFox

Better start to do some reading of the 17th ed 7671...... got my 2382-20 course at local college on the 28th.

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#### Shakey

sat mine today

just happened to get ooh, give or take, 100 percent

thats 30 out of 30 then

Get in!!!

good luck with yours!!!

B

#### Bane

Congratulations Shakey!

Glad I was of some help.

(No, seriously. Don't thank me)

C

#### Cirrus

Well, I got the same answer as Easyfox so don't feel too bad. Well done today Shakey - 100% is a good result!

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#### MacSparky

Nice one shakey, was you back home in time for tea and medals or did you use the full hour?

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#### EasyFox

100% shakey spot on matey.

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#### Shakey

Nice one shakey, was you back home in time for tea and medals or did you use the full hour?
erm.... dont like to push the chest out too much

it was 11 minutes

but i am QUITE familiar with the book, and i probably had a good run of questions.....

sorry

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#### SteveH37

got to sit mine tomorrow (saturday FFS)

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#### Darius-parky

I passed my 16th in May 2006. Do I need to the 17th Edition now?

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#### Shakey

I passed my 16th in May 2006. Do I need to the 17th Edition now?
you need to do the 17th edition

when you do it is entirely up to you Darius

altough if you are going to start working to the 17th, as you can now, and wull have to after Jul, then naturally, you will need to know the book

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#### SteveH37

Well, what a farce..........

Turned up in plenty of time, me and 11 others all sat ready to start online test.

exam details.................

WRONG EXAM!

Up we get and leave........

oh well, got to my private job a bit earlier

#### LukeScotty

##### -
Arms
whats the difference between the two? is one the update??

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#### Shakey

whats the difference between the two? is one the update??
2382-10 is the full 17th, 2382-20 is the update

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#### SteveH37

Just sat mine, PASSED

#### LukeScotty

##### -
Arms
well done steveh37, was it the update or the full en? what score you get?

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#### SteveH37

dropped a few % on selection/erection (87.5% booooo) but otherwise 100%

was the update course after 1 day with a very rough and keen to return home lecturer.

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