Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam

On Monday, 5 March 2018 20:13:32 UTC, ARW wrote:
You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Join what to what? Phase to phase?

I'll guess the 3PH MCB as it has overcurrent on two phases.

Owain

ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

Jim K wrote:

ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)

Purely from domestic experience I reckon one or both B20 MCBs while the
13A fuses are in a brief molten/vaporised state. But also no expert.
It may be possible to calculate whether the C63A should trip before the
others have time to open.

--

Roger Hayter

On 05/03/2018 20:13, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

What was the PSSC at the supply end?

(although I am guessing since you asked the question probably the 63A
3ph MCB ;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 05/03/2018 20:13, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.


The apprentice who joined them?

--
Robin
reply-to address is (intended to be) valid

On 05/03/2018 21:23, John Rumm wrote:
On 05/03/2018 20:13, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

What was the PSSC at the supply end?



Greater than 12KA according to my test meter.

The same as my house supply!

(although I am guessing since you asked the question probably the 63A
3ph MCB ;-)



Not saying ATM :-)




--
Adam

On 05/03/2018 21:42, Robin wrote:
On 05/03/2018 20:13, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with
some 16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.


The apprentice who joined them?


Only if he is connected to the company fuses.

On Monday, 5 March 2018 20:13:32 UTC, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam

What you are talking about is called "discrimination".
Google electrical discrimination
Eg
https://news.voltilink.co.uk/article...discrimination

A whole sub-subject of electrical distribution

You trying to blow yourself up or what?
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"ARW" wrote in message
...
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through 13A
SFCUs with 2.5mmT&E and join them at the load side of the SFCUs about 30m
away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam

On 06/03/2018 08:28, harry wrote:
On Monday, 5 March 2018 20:13:32 UTC, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam

What you are talking about is called "discrimination".

That would be a woosh then from harry ;-)




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Monday, March 5, 2018 at 8:13:32 PM UTC, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam

Whichever will be the biggest pain in the arse when it blows/trips.

Philip

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)




I did not know the answer to this one myself until someone actually
tried it:-)

And the answer is "that every fuse and MCB tripped/blew including the
C100A main switch".

Only the main incoming fuses did not blow and I have no idea what rating
they are and I have no way of finding out even if I wanted to as someone
has installed a steel pillar in front of the incomer.


--
Adam

On 06/03/2018 16:52, John Rumm wrote:
On 06/03/2018 08:28, harry wrote:
On Monday, 5 March 2018 20:13:32 UTC, ARWÂ* wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam

What you are talking about is called "discrimination".

That would be a woosh then from harry ;-)


Probably got his phases mixed up:-)



--
Adam

ARW wrote:

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)




I did not know the answer to this one myself until someone actually
tried it:-)

And the answer is "that every fuse and MCB tripped/blew including the
C100A main switch".

Only the main incoming fuses did not blow and I have no idea what rating
they are and I have no way of finding out even if I wanted to as someone
has installed a steel pillar in front of the incomer.

Is that unsurprising? There may be a fault current high enough for the
breakers to be disengaged before the springs have time to accelerate the
contacts apart?

--

Roger Hayter

On 06/03/2018 19:22, ARW wrote:
On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)




I did not know the answer to this one myself until someone actually
tried it:-)

And the answer is "that every fuse and MCB tripped/blew including the
C100A main switch".

Only the main incoming fuses did not blow and I have no idea what rating
they are and I have no way of finding out even if I wanted to as someone
has installed a steel pillar in front of the incomer.

My experience of a complete failure of discrimination was when a total
idiot closed the three phase breaker to a test stand without checking
with anyone or warning anyone. It was supplying a 3ph, 11kV, 2.5MW motor
.... which had shorting bars connected across the phases. The local
breaker shot straight back out, as did the one in the distribution room,
plus the electricity company's breaker in their panels in the same room
and the one in the substation supplying the factory, and the one
supplying that and presumably even the one supplying that, as not only
the factory and offices, but the whole of Wythenshawe was off for more
than three hours!

SteveW

On 06/03/2018 20:49, Roger Hayter wrote:
ARW wrote:

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)




I did not know the answer to this one myself until someone actually
tried it:-)

And the answer is "that every fuse and MCB tripped/blew including the
C100A main switch".

Only the main incoming fuses did not blow and I have no idea what rating
they are and I have no way of finding out even if I wanted to as someone
has installed a steel pillar in front of the incomer.

Is that unsurprising? There may be a fault current high enough for the
breakers to be disengaged before the springs have time to accelerate the
contacts apart?


I would not have expected the C100A main switch to have blown due to the
resistance of the 2.5.

--
Adam

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)


And my second question is how many laptops fried?

--
Adam

On Wed, 07 Mar 2018 18:11:36 +0000, ARW wrote:

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with
some 16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)


And my second question is how many laptops fried?

None of them. However, I think you were really wondering how many
plugged in laptop charging bricks (connected or not to their respective
laptops) got fried, in which case, pretty well all of them.

--
Johnny B Good

On 07/03/2018 19:14, Johnny B Good wrote:
On Wed, 07 Mar 2018 18:11:36 +0000, ARW wrote:

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with
some 16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)


And my second question is how many laptops fried?

None of them. However, I think you were really wondering how many
plugged in laptop charging bricks (connected or not to their respective
laptops) got fried, in which case, pretty well all of them.


Actually my suggestion was that it was the chargers. But where there's
blame there is a claim and this lot are making the most of it (but they
do not know what actually happened).

I am glad it was not my cock-up (and I have made plenty).

--
Adam

ARW wrote:

On 06/03/2018 20:49, Roger Hayter wrote:
ARW wrote:

On 05/03/2018 20:19, Jim K wrote:
ARW Wrote in message:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

--
Adam


The 20A MCB?
(uneducated in electricals)




I did not know the answer to this one myself until someone actually
tried it:-)

And the answer is "that every fuse and MCB tripped/blew including the
C100A main switch".

Only the main incoming fuses did not blow and I have no idea what rating
they are and I have no way of finding out even if I wanted to as someone
has installed a steel pillar in front of the incomer.

Is that unsurprising? There may be a fault current high enough for the
breakers to be disengaged before the springs have time to accelerate the
contacts apart?


I would not have expected the C100A main switch to have blown due to the
resistance of the 2.5.

Quick back of envelope (but calculator aided) calculation gives total
resistance between phases 540mOhm, current 740A, divided by 63 equals
11.8 so it is within spec for the C63 to trip as fast as it likes (no
min time). So even if it's surprising it is within specs. BICBW

--

Roger Hayter