Numerous DIY questions.

[r.b]

In a house scenario as long as lights outside,sockets outside are rcd protected there is no need for rcbo's this right?

 

[batty]

Only if they have some sort of circuit protection MCB/fuse.

 

[NozSpark]

Eh?

Domestic wise..

All sockets require RCDs

All circuits within bathroom require RCDs

All burried cables require RCDs

 

[SPECIAL LOCATION]

Do you understand the concept of MCB's, RCD's, RCBO's ?????

maybe not by the question......?

lets hope you are not working alone in peoples houses!!!!!!!! :_|

:C

 

[r.b]

Whats the best method of cable and fuse selection?.Is it the wattage divided by voltage to give design current then you pick a fuse to cover this.Then the cable selection the current carrying capacity has got to take the design current so the current carrying capacity has got to be higher than the design current?.Unless you have a better method?

 

[Technician]

You need to look in the current issue of the On Site Guide.

The process begins with design current, then choice of the

rating of the device under consideration, followed by an

application of de-rating factors which will give a value that

should be less than the tabulated value in the regulations

for that specific installation method.

Please understand that if you are not familiar with this process

you should ask a person more experienced and qualified than

yourself.

I am sure a lot of people here would agree and assist where

possible.

 

[Doc Hudson]

You need to take into consideration the length of the cable run and fixing methods to allow for your cable de-rating due to things like grouping or buried under insulation and the volt drop etc. Remember the cable has to be able to supply the loads current requirements and the protective device is to protect the cable not the load, so you need to establish the minimum CSA cable needed to supply the load before you can have any idea of what protective device you need. This is normally covered in the City & Guilds electrical installation courses. There were numerous questions about designing circuits for various domestic & commercial environments taking in all of the combinations of derating values.

Doc H.

 

[r.b]

Just looked at the formula it> In

divided

caxcgxcixcc rather than buy a wiring regs are all the grouping factors in the on site guide?

 

[Technician]

Yes they are but that, I think, is the OLD on site guide.

As Doc Hudson says, conductor length MUST be taken

into account.

In addition, there are other assessments that MUST be

carried out on the protective conductors.

You must be VERY careful how you apply this.

I respectfully suggest that you may be out of your depth.

The full regulations is a very difficult book to digest without

guidance.

 

[SPECIAL LOCATION]

Just looked at the formula it> Individed

caxcgxcixcc rather than buy a wiring regs are all the grouping factors in the on site guide?

eh????

are you asking about JUST grouping factors?

or all rating factors that affect a cables current carrying capacity

? Ca Cg Ci Cf

Either way the On Site Guide

(Appendix 6 pg 123 - 134 red copy / Appendix F pg 139 - 150 green copy)

does not have all the full tables that appear in BS7671

(Appendix 4 pg 253 - 317 red copy / Appendix 4 pg 304 - 375 green copy)

The pages in the wiring regs are bigger and there are more of them..

and there is more information...

You NEED to buy both....

Unless your work attire includes a John Wayne hat & saddle..

In which case you need neither..

I assume at the moment you have neither as you don't know whats in the OSG or BS7671..

BUT...

how are you doing rewires etc.. without copies of the regs??????

http://www.talk.electricianforum.co.uk/question-answer-board/18087-extension.html

:_|

p.s...

PLEASE dont anyone pipe in saying I havent answered the question!

as some tend to like doingheadbang

 

[r.b]

Technician you mention length is this required in the second part of the next calculation after the first which I mentioned earlier.Volt drop mvXibXlength

divided by a 1000

This is within 3% lighting 5% all other uses?

 

[Technician]

Yes; that is correct. The tables are to be found Appx 4

opposite the tables for tabulated values of current within

reference methods.

The OLD OSG has been superceded as Special Location

has stated.

 

[Andy™]

rather than buy a wiring regs are all the grouping factors in the on site guide?

er... you aint going to get far without a copy of the regs. how do you plan on working to them if you dont know what they are

:red card

 

[r.b]

I was looking at the green on site guide today I might buy it because it near enough has all the stuff you need tables etc for cable selection.Does it have k values didnt see this as I had a quick browse through?

 

[kme]

FFS!!!!!!!

It was clearly stated in your other post, where you inferred the intention of buying an OSG, instead of a 7671.

Lets put this in words of a single syllable, shall we? You will need BOTH (unless you`re a "bodgit & scarper" type :head bang)

If you won`t take constructive, helpful advice.....why ask.

FYI: NO, they`re not in the new OSG, AFAICR. They ARE in the BGB, along with all the other factors and calculations needed.

KME

 

[Doc Hudson]

I have merged these threads r.b. as the content is very similar it would only clutter the forum if every member started a brand new thread each day on a continuing topic already raised. I had also moved these to the student zone as I had assumed anyone who hasn't got either the on-site-guide or BS7671, (preferably both), is probably not working out unsupervised on real jobs. Are you on a college / fast track course? it may help to ask the tutors what is the best to have in relation to the course content.

Doc H.

 

[Andy™]

I was looking at the green on site guide today I might buy it because it near enough has all the stuff you need tables etc for cable selection.Does it have k values didnt see this as I had a quick browse through?

buying OSG and not the regs is a bit like buying an insulation resistance tester, but nothing to check continuity or do live tests...

 

[r.b]

I was on a domestic site and basically a spur and timeclock was next to a boiler.A feed came down to the spur with a flex going to the boiler l,n,e.A l,n and earth link went into timeclock from spur.The timeclock and thermostat had a 3 core 1.5 installed between them.From the time clock it was a 4 core flex.I just need to know the four core flex connections at the time clock and at the other end of the flex at the boiler?I presume brown feed, black sw stat and grey neutral any ideas? Plus the 3 core flex at the boiler I presume l,n,e like normal

 

[r.b]

With these they have a timer and a night day setting.I just put a line,neutraul and earth into the fitting.At the fitting connections whats the 4th terminal for its black or sometimes red?.The 3 other terminals Ive been using these line ,neutral and earth.

 

[Electroglow]

Usually should only need a live and nutueral feed.

Yes most of the pir lights do come with built in timers

And if you only have a live and nutueral at the light fitting the spare connector should be left blank as you don't have any other cores lol