TT PFC question

pevvers · Jul 20, 2009

Yeah, I've always been told just to double it for 3 phsase, never heard of anyone wanting it as accurate as taking decimal places into it....

This installation is single phase though.

electricAl · Jul 20, 2009

Doubling it is fine, always was & always will be. It errs on the side of caution.

But as someone was being more precise - i was, well, more precise

Not like me really

matt456 · Jul 20, 2009

so the reading i need to put in the box for the pfc is the lower value of 93A?

pevvers · Jul 20, 2009

Well, if you go by GN3, then it will be the higher, i.e. the 470A from the PSCC (0.47kA).

Honest!!

Lou7 · Jul 20, 2009

The reason I used the 1.74 was that I had a reading that put me over, and was told that I could use that instead of doubling,giving a lower result. I thought it was 400 divided by 230

Record the highest.

or was 415/240 ?

pevvers · Jul 20, 2009

Lou7 said:
The reason I used the 1.74 was that I had a reading that put me over, and was told that I could use that instead of doubling,giving a lower result. I thought it was 400 divided by 230

Yup, completely agree with that as the doubling is only a rule of thumb as it's simple to do on site. I must remember that in case I get any borderline results someday...

Why would it be root 3 electricAL? I'm always looking to learn new stuff... Root 2 I've heard of, but never 3.

electricAl · Jul 20, 2009

pevvers said:
Yup, completely agree with that as the doubling is only a rule of thumb as it's simple to do on site. I must remember that in case I get any borderline results someday...

Why would it be root 3 electricAL? I'm always looking to learn new stuff... Root 2 I've heard of, but never 3.

The root of 3 is intrinsic with TP systems.

It`s the maths behind how we derive 400v between phases from a 230v to earth supply...

230 x root of 3 (1.732 is near enough but it`s really 1.73205081) = 400

Works in reverse too, of course... 400 / 1.732 = 230

Originally it was 240v x root 3 = 415v

scotsparky · Jul 20, 2009

400 devided by root 3 = 230

matt456 · Jul 20, 2009

thanks to everyone who has helped me!
new question coming soon

electricAl · Jul 20, 2009

scotsparky said:
400 devided by root 3 = 230

Harhar...beat ya too it

Is it just the eld uns that know this kind of thing?

scotsparky · Jul 20, 2009

the young ones are taught it but if anything like me it takes a few years to sink in. The young one are to busy thinking about what they did to the young girls on sat night. I was

See pic on how we get the figures.

electricAl · Jul 20, 2009

scotsparky said:
the young ones are taught it but if anything like me it takes a few years to sink in. The young one are to busy thinking about what they did to the young girls on sat night. I was

go on, go on...we`re all dying to know!

you was what?

Personally couldn`t wait til Saturday night - Friday came sooner

Arhhh, memories, mamories. Such a long time ago...

scotsparky · Jul 20, 2009

gave more info not bad for a monday night!

pevvers · Jul 20, 2009

I'm pretty sure I must have learnt it, or something along those lines in my HNC, but that was 6 years ago and I haven't used anything in it since.

Sounds about right though, cheers for the info,

scotsparky · Jul 21, 2009

well i remebered it from 18 years ago

TT PFC question

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