Todays PIR

[Sidewinder]

OK,

Finished a PIR today, reports etc. still to do, may post some pics if I get a chance a bit busy at the moment with several things, some good some very bad!

OK. Industrial/commercial premises. PME supply.

Incoming mains, fuses must be equal to or less than 100A, industrial thus I would guess BS88's. Taking these as 100A.

Reason for rating, direct current metering, anything >100A requires CT's.

Straight into an old panel board. No on site HV transformer.

Main fuse switch (MS) rated at 600A, 5 sub main switch fuses/fuse switches (FS) etc. in panel board, with a few other bits not relevant.

FS: 2 rated @ 200A (FS4 & 5) , 3 rated @ 100A (FS1-3).

All 3ph.

Fuses as follows:

DNO: 100A

MS: 600A

FS1: 63A sub main feeding 6 way TP board with Final Cct's & 3 further sub mains, including 3 to buildings remote to the origin

FS2: 30A sub main feeding site boiler/heating controls no final cct's all heating/boiler controls cct's

FS3: Spare

FS4: 200A sub main feeding separate building

FS5: 150A sub main feeding in building DB final cct's only

I'm not asking for advice, I know my results & my responses, (our! ) just posting this for comments and to add to the "knowledge base" working on the PIR paperwork & report now.

Just looking for the "learners" to comment for their benefit. I'm NOT going to post my comments etc. until this has been debated a bit for the "trainees" / "inexperienced" to discuss this with those "in the know".

Trying to help?

Paul

p.s. may not be able to check back too often, but lets go with the flow.

There is another who knows the install here...

 

[green-hornet]

Oh dear

I think I will let some educated to answer first so I can say see I told you so.

 

[Riggy]

Over an hour. Do none of you want to learn? ROTFWL

Is it me? ROTFWL

 

[green-hornet]

Looks like we may have to go first

Wet Fish

 

[Sidewinder]

I was a bit disappointed!

I thought I would have at least got some comments even if they were sod off you fool! (OR words to that affect!)

More to come BTW.

If things go well I'll reprise the RCD thread too, this is a little easier to do though as the work is all in my head as I did a lot of it so I don't have to think about what others have done/thought propose to do etc. thus less thinking time!

Paul

:_|

 

[kme]

OK mate, put `em out of their misery.

I saw something I`d never come across before - a 20mA RCD!!!

Who`s got suggestions how you`d test such an animal? (p.s. we DO know, just quizzing.)

KME

 

[Riggy]

Looks like people don't being "teachered".

I think you may have mis-read your audience!

 

[m4tty]

Well I got to admit that's way beyond me

 

[M107]

Always willing to learn so I'll go first.

If I'm reading right you have;

100A suppliers fuse straight into panel board with no means of isolation?

Lack of discrimination between suppliers 100A & main switch fuse @ 600A?

Thats a start somebody elses go now.

I shall hide myself away....bet I'm wrong.

 

[ElectekAir]

Incomming too small???

Can't be fuses would have gone by now:_|

 

[wozz]

punching above my weight here as this is not the sort of thing i ever get involved with. But in terms of discrimination is it worth trying to discriminate with a 100A suppliers fuse? Surely the FS fuses would have to be much lower to achieve this and therefore not practical?

 

[M107]

OK mate, put `em out of their misery.I saw something I`d never come across before - a 20mA RCD!!!

Who`s got suggestions how you`d test such an animal? (p.s. we DO know, just quizzing.)

KME

Only ever seen one in use as protection for a control panel.

Never tested one & never been told how to so at a guess test as a time delay

 

[Sidewinder]

OK I have a few minutes in between writing up the PIR.

I need a break, I'm on 31 pages so far & I have only got one board schedule so far, we have 50 defects and counting, and basically all the Code 1's were remedied prior to leaving site!

Working backwards through the posts,

M107,

The 20mA RCD is an instantaneous device thus you cannot test as a time delay.

Also it is quite old and specialist with built in earth fault monitoring. You cannot test on the outgoing terminals of the internal disconnect device as the sensing loop is external to this! The outgoing supply cores go through the sensing device to the disconnect device. It is almost a modular RCD device. KME & I came up with a method to test, but I have found another method since.

Wozz,

Ycs you should try to discriminate with the DNO fuse. This install has 2 tenant supplies, and as well as the 3 sub mains from the main panel board, one of the DB

 

[kme]

KME & I came up with a method to test, but I have found another method since. :coat

And when are you going to enlighten me, O uber-clever one?

Intrigued, I am (yoda-voice)

 

[green-hornet]

I think this is a very good subject, and one WE ALL can learn from, the lack of input suggests to me that no one is bold enough or confident enough to answer.

You have to remember that right or wrong does not matter, when an oppertunity to learn comes along, there is not one single member of this forum going to riddicule any one who has a go.

The question is this, do you really want to learn? or are you happy to wait for some other member to answer everything and then learn by second hand.

Ok I will go first.

First point raised is the in comming supply that was tested, if its three phase at 100amp per phase, there are some major safety factors as to why the set up of the section board is such as those you would expect on a larger more substantial supply for example a 400amp or 600amp supply. ]

 

[Sidewinder]

And when are you going to enlighten me, O uber-clever one?Intrigued, I am (yoda-voice)

I love being cryptic on times.

You've read the answer in another thread, one you started my friend!

You even thanked me for the post!

A programmable device you seek. (Yoda voice)

 

[wozz]

These are the sort of threads i love, why? because i dont know much about it all and like to learn.

If im barking up the wrong tree please do tell me if not i would like to have a go. ok so we shall try to discriminate with the 100A service fuse. I have a rough idea of how o do this but could you explain to me how to work this out and what you are trying to achieve.

 

[Sidewinder]

IMHO we should try to discriminate with the DNO fuse, however, as yet we have only fused down the final circuits according to the connected wiring csa as we were unable to trace and identify all of them.

Once the final ccts are identified we will reverse engineer the loads and then look at getting some discrimination into the system.

One issue is that with 88's at high fault levels then pre-arcing time comes into the equation as does the energy let through i^2t, and the energy dissipation across the fuse. As will the true loop impedance, not the loop resistance we measure. The available fault current, any DNO fault current limiting, and a few others that I can't think of this second.

Bgeen out working this am, got to make my lad some grub then qualy is on so will be popping back & fore, will leave the forum up on the laptop though.

So lets have a go.

100A BS88 DNO fuse > Main switch fuse with 600A, what are we going to change these to, or are we?

Or, do you want to work the other way that is upstream from the final circuits to determine the loadings?

This is a bit of a 2400 exercise in reverse...

 

[green-hornet]

I think it would be best to work in reverse, that way we can calculate the loadings and then adjust the fuse requirements accordingly, I am now looking forward to this excersise

 

[Sidewinder]

OK GH but we'll have to wait for some of the remedials to get the final circuit loadings as there are 5 DB's plus the remote building which has at least one DB, not part of our remit yet! Along with the tennant site cabin.

I think it ammounts to about 70 fuses/mcb's including the tennant cabin excluding the remote building and the other site cabin connected to that.

BTW I agree that the working upstream is the way to go, also it is how it was taught on my 2400 course.