Numerous DIY questions.

[Technician]

3 phase pfc readings I know you take the highest reading and double it.For instance you might get a reading of 15ka, you might have bs 88 fuses protecting and these are rated at 80 ka so this would be ok wouldnt it?This how it works if ever a big fault occured yoy dont want the board blowing off the wall.Household breakers are 6ka so you are looking for a pfc reading under 6ka am i getting this right?

Do not forget that you need to have the reads

of PEFC (Prospective Earth Fault Current) AND

PSSC (Prospective Short Circuit Current) and

one may be larger than the other. The greater

one is the one that concerns you.

 

[LNRDF01]

you seem to worrying about breaking capacity of the fuses, when you will get no where near the fault current that will damage them. The fault current you measure is important so you can compare the result to the ones in the time/graph characteristics in the regs book, i.e 160 amps minimum for a BS 60898 circuit breaker or approx 600 amps for a BS88 100 amp fuse.

 

[kme]

erm........Perhaps not!

We`re talking about PFC/PSCC, which can be in the thousands of amps. Try to keep up at the back, please

 

[Jono Pashley]

meh...just lately i struggle to keep up at the front

 

[SteveT]

meh...just lately i struggle to keep up at the front

Try Via8gra

 

[Technician]

I think KME has hit the nail on the head

in this thread. I recently saw one of the

most recent testers from Megger (forget the

number) used to measure PEFC and PSSC AND

fault current between lines, thus removing

the need to double the reads.

 

[apprentice87]

Hi Technician,

Yes, i got one!! My megger 1730 will do phase to phase up to 20KA which is plenty enough for supplies of up to 100A i would think.

As it happens, anyone know why they say to double the single phase, phase/neutral reading???

Assuming that the neutral is the same size in the supply cable [which i am fully aware is not always the case] would it not be 1.732 times the single phase reading?? Is the double it idea to cater for cases where the neutral is smaller??

john..

 

[Technician]

You wizz kid, John!

---------- Post Auto-Merged at 11:02 ---------- Previous post was made at 10:57 ----------

I may have this SLIGHTLY wrong but

I think the correct multipler is

1.732. To keep on the right side,

I was told that the multiplier is

2 but someone may correct me.

 

[Andy™]

Assuming that the neutral is the same size in the supply cable [which i am fully aware is not always the case] would it not be 1.732 times the single phase reading?? Is the double it idea to cater for cases where the neutral is smaller??

john..

doubling the number doesnt require use of a calculator

 

[r.b]

I have done plenty of new installation testing.I know its a report on sometimes older installations that in some cases arent up to todays standards.End of the day you have got to make a decision satisfactory or unsatisfactory.I know you have to look out for everything.6mm to water and gas is a classic should be ten.what if its old wylex board could you just write down could do with upgrading to rcd protection etc end of the day its got to be safe.You have got to decide on a code to give?

 

[NozSpark]

A good start would be to read the ESC best practice guides

As it's a report it shouldn't contain your beliefs, it should be inspected and tested to the current regs (taking into account the regs when it was installed) and be based on fact and not opinion

Whats wrong with 6mm on an existing installaton anyhow?

 

[Sharpend]

I thought it was a classic because it's been around for years?

 

[paul b b]

R.b

You can download the guide for free.

 

[Doc Hudson]

I have done plenty of new installation testing.I know its a report on sometimes older installations that in some cases arent up to todays standards.End of the day you have got to make a decision satisfactory or unsatisfactory.I know you have to look out for everything.6mm to water and gas is a classic should be ten.what if its old wylex board could you just write down could do with upgrading to rcd protection etc end of the day its got to be safe.You have got to decide on a code to give?

Said the person who only recently found out how to size cables, terminate outside lights, what the OSG contains etc. r.b. I have merged a whole group of your recent new threads together as they all come under the same banner of "DIY out of their depth" or "struggling student". The content of most of these questions does not reflect the typical standards of anyone who has attended and passed any college courses or formal training. Some may consider them a bit of a wind up, I will leave others to draw their own conclusions by reading some of your past threads, now all contained in this one thread. Also from the evidence of your past questions I would suggest you are not yet competent enough to do any periodic inspections.

Doc H.

 

[Technician]

I have done plenty of new installation testing.I know its a report on sometimes older installations that in some cases arent up to todays standards.End of the day you have got to make a decision satisfactory or unsatisfactory.I know you have to look out for everything.6mm to water and gas is a classic should be ten.what if its old wylex board could you just write down could do with upgrading to rcd protection etc end of the day its got to be safe.You have got to decide on a code to give?

Gn 3 states that the purpose of the periodic is to

show that the installation remains safe to use. It

is not the intent of the periodic to bring any older

installation up to a "modern" standard.

As to coding, C1 means immediate danger to the

user.

A C2 is still serious BUT another event has to take

place before the danger is manifest to the user.

 

[SteveT]

Eh?Domestic wise..

All sockets require RCDs

All circuits within bathroom require RCDs

All burried cables require RCDs

What about dedicated freezer socket!

 

[NozSpark]

Steve,

You need to take that post (Dec 2011 BTW) in context with the question asked aswell as others at that time by the OP.... Some peoples questions lead me to beleive that they are extreemley inexperienced and don't understand the regs so I occasionally (in those circumstances) over simplify my replies so as to not confuse the issue

 

[SteveT]

Steve,You need to take that post (Dec 2011 BTW) in context with the question asked aswell as others at that time by the OP.... Some peoples questions lead me to beleive that they are extreemley inexperienced and don't understand the regs so I occasionally (in those circumstances) over simplify my replies so as to not confuse the issue

Ok accept your explanation, just thought it was a bit generalised...but in the circumstances!! all noted

 

[Andy™]

What about dedicated freezer socket!

only if the cable doesnt require it (i.e not chased into a wall), or TT