Garage CU

[Electrifying]

You can't go blindly changing MCBs for larger ones. The MCB may be of that rating for a reason. Not just cable calcs.

The MCB could be supplying another cable of a smaller size somewhere. Or the cable has been joined somewhere with a smaller cable. Or the electrician only had a 16 amp MCB. Who can say? The possibilities are endless. Never assume anything without checking.

I'm sure if this had been the case it would have been mentioned - extra conductors in the MCB / joints in the cable

 

[ban-all-sheds]

You appear to be getting confused between the design current and the rating of the OPD.

No I am not.

You appear to be getting confused between the discussion about whether a B32 is appropriate in this specific situation, and this:

present me with a genuine scenario where the current carrying capacity of our 6mm conductor, from house to garage, drops below 32A.

Volts drop is based on the design current, NOT the In of the OPD - In must be lower than the rating of the cable and higher than the design current, that is all - In has NO BEARING ON VOLTS DROP WHATSOEVER.

I never said it did - I was just answering this:

present me with a genuine scenario where the current carrying capacity of our 6mm conductor, from house to garage, drops below 32A.

And in that case, where Electrifying had specified a current of 32A, voltage drop means that a 6mm² cable becomes non-compliant, i.e. its ability to carry the current specified and stay within the regulations stops, at 29.5m.

Please try and learn to read properly, and to pay attention.

 

[ban-all-sheds]

Thank you, loverocket, I was about to reply myself then read your post.

You would be better advised to read your own posts, because you seem not to understand what they say.

Three times he said it and three times he got it wrong, but I bet we still don't get an apology.

I'll say it 4 times, if you like, or 40 or 4,000,000.

And no - you won't get an apology, because I am not wrong.

Volt drop and cable length has no bearing on the current carrying capacity of the cable.

So you never take account of voltage drop when designing a circuit?

You never say "no, this cable cannot carry that current over that distance"?

If you do then what you are saying is that the capacity of the cable is insufficient. Voltage drop is a characteristic which imposes a minimum csa just like temperature rise does. In fact they are closely related because they are both due to the resistance of the conductors.

The genuine scenario I asked for, ban-all-sheds, is in relation to why I was wrong to recommend upgrading the MCB to 32A for a 3-core 6mm SWA cable.

Because it then becomes a 32A circuit, and it may not be suitable to be used as such.

No-one has come up with a valid reason, backed up by regulation or calculation, as to why it was wrong/dangerous for me to do so.

525.

That's 3 times now I've told you that - if you get it wrong a 3rd time will we get an apology from you?

 

[Steve]

Gosh, what did I miss last night

I love a good arguement!

 

[mikhailfaradayski]

 

[bongos]

there's a special exception made for rings and spurs from rings..
there isn't however a special exception made for garage feeds..

No there isn't, it's just how it works.

What about 433.1.5?