9" grinder trips 16amp MCB

[aptsys]

For what it's worth, I'm not an electrician but there is bare copper showing on those cables.
Also I HATE seeing mcb's not in sequence. i.e. all 6's at the start, followed by 16's, 20's 32's etc)

There's an exposed copper busbar. A small amount of copper on the conductors is not a problem.
There's no requirement or need to have MCBs in any kind of sequence other than a logical order for the circuits. The busbar is rated for the full load across the length.

 

[Taylortwocities]

There's no requirement or need to have MCBs in any kind of sequence other than a logical order for the circuits. The busbar is rated for the full load across the length.

Correct. Back “in the day” the bus bars in the old fuseboxes were not as big and the advice from manufacturers was to use the higher fuses nearest the main switch.
It’s not needed now. If it were, The CU makers would stipulate it on the installation instructions. But like a lot of things, many people just do what was the norm back in the mists of time.

 

[conny]

Last time I wired a CU was about 30-40 years ago and we were taught in college to group them from the lowest on the left to highest on the right.

As I said, I have mild OCD and it just looks neater. LOL

 

[EFLImpudence]

Last time I wired a CU was about 30-40 years ago and we were taught in college to group them from the lowest on the left to highest on the right.

Is that irrespective of which side the Main Switch is?

 

[JohnW2]

Correct. Back “in the day” the bus bars in the old fuseboxes were not as big and the advice from manufacturers was to use the higher fuses nearest the main switch.

Is that really true? Although it is certainly true that that was the manufacturers' advice (indeed ones like the Wylex Standard would only 'allow fuses >30A to be installed adjacent to the main switch, those were the days in which they were over-engineered (and 'beautifully engineered) - and I suspect that the bus bar of, for example, a Wylex one would put modern ones to shame!

It’s not needed now. If it were, The CU makers would stipulate it on the installation instructions. But like a lot of things, many people just do what was the norm back in the mists of time.

True - but, mind you, there are other sort-of-related things that the manufacturers do currently 'stipulate' which I strongly suspect most people ignore (even if they are aware of them). For example (as we have discussed in the past, Wylex say of their MCBs ..

Kind Regards, John

 

[Taylortwocities]

Bet they only put the adjacent MCB notice in after their “MCBs frying tonight” episode!

 

[JohnW2]

Bet they only put the adjacent MCB notice in after their “MCBs frying tonight” episode!

I think that statement, or a similar one, has actually been in their technical documentation for decades. The extract I posted came from a 2007 document, which is the oldest I can currently find.

Kind Regards, John

 

[conny]

Is that irrespective of which side the Main Switch is?

In my youth, (longer than I care to remember LOL), I don't think I ever came across one that didn't have the main switch to the right of the fuses/mcb's.

I know that these days they can be in a number of positions but as I don't work on them I've never given it a thought. To be honest though, if I was to work on one with the main isolator in a central, or left hand, position I would probably still mount them with the lower rated to the left regardless of which side of the switch they were.

 

[JohnW2]

In my youth, (longer than I care to remember LOL), I don't think I ever came across one that didn't have the main switch to the right of the fuses/mcb's. ... I would probably still mount them with the lower rated to the left regardless of which side of the switch they were.

Same in my youth (and same comment about mine ).

Maybe, in addition to 'neatness', that's how the 'lowest-rated on the left' came about - since it resulted in the highest-rated one being adjacent to the Main Switch?

Kind Regards, John

 

[EFLImpudence]

In that case, it seems odd that the teaching was not ' highest on the right'.

 

[JohnW2]

In that case, it seems odd that the teaching was not ' highest on the right'.

There's not really any material difference between 'highest on the right' and 'lowest on the left', is there?

Given that the two are equivalent, the fact that people tend count 'upwards', and read 'from left to right', it is perhaps not too surprising that people are more inclined to think of the latter, is it?

Kind Regards, John

 

[EFLImpudence]

There's not really any material difference between 'highest on the right' and 'lowest on the left', is there?

Not when completed, but they would be fitted 'from the right'.

Given that the two are equivalent, the fact that people tend count 'upwards', and read 'from left to right', it is perhaps not too surprising that people are more inclined to think of the latter, is it?

Then the question is why the main switch was on the right.

 

[JohnW2]

You seem to bve making a bit of a meal out of this! ...

Not when completed, but they would be fitted 'from the right'.

Why?

Then the question is why the main switch was on the right.

Well, it had to be somewhere (left, right, or 'in between') - maybe they tossed a coin! Mind you, I suppose that 'in the middle' would have minimised busbar path lengths, but they don't seem to have thought of that!

Kind Regards, John

 

[EFLImpudence]

You seem to bve making a bit of a meal out of this! ...

Yes, I am replying to myself.

Why?

Logic.

If there were only one MCB would you put it on the left of the busbar?

Well, it had to be somewhere (left, right, or 'in between') - maybe they tossed a coin!

Then with so little thinking, why was it deemed necessary to 'teach' lowest rated MCB on the left?

Mind you, I suppose that 'in the middle' would have minimised busbar path lengths, but they don't seem to have thought of that!

You have the Neutral to get past.

 

[JohnW2]

Logic. If there were only one MCB would you put it on the left of the busbar?

Probably not. I confess that I've been thinking about a 'fully (or nearly fully) populated' fusebox/CU/

Then with so little thinking, why was it deemed necessary to 'teach' lowest rated MCB on the left?

I think I've already covered that. If, having tossed a coin (or whatever), they decided to put the Main Switch on the right, they might have felt that it was best to have 'highest-rated on the right' - which, in a fully-populated box would be the same as 'lowest on the right'.

You have the Neutral to get past.

It would certainly not be beyond the wit of man to get around that issue - for example, the L busbar could "detour around' the neutral connection.

Kind Regards, John
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