Radials vs Rings

[bernardgreen]

I see Boone's table has 2.5mm rated at 18.5A (lowest) in a wall and 30A free (highest). So, I would assume a mixture of the two (most free under floors) would be around 25A per 2.5mm cable.

The 25A current when passing through the area of 18.5A installation would overheat that section of the cable as the heat produced in the copper could not be disapated from the outer surface of the cable

Stop trying to justify wiring a 20A oven onto a ring circuit.

 

[dingbat]

I have seen some 40A mcbs on general ring circuits in new homes. I see Boone's table has 2.5mm rated at 18.5A (lowest) in a wall and 30A free (highest). So, I would assume a mixture of the two (most free under floors) would be around 25A per 2.5mm cable. That gives a theoretical maximum of 50A on the ring.

See what happens when we guess?

Much to learn, I think.

 

[johnsville]

I see Boone's table has 2.5mm rated at 18.5A (lowest) in a wall and 30A free (highest). So, I would assume a mixture of the two (most free under floors) would be around 25A per 2.5mm cable.

The 25A current when passing through the area of 18.5A installation would overheat that section of the cable as the heat produced in the copper could not be disapated from the outer surface of the cable

Stop trying to justify wiring a 20A oven onto a ring circuit.

I am just musing not justifying anything. I see there is capacity left for safety reasons. The oven actually draws under 16A.

I see BS and what is electrically sound may conflict. BS are not the regs I believe.

 

[ban-all-sheds]

I have seen some 40A mcbs on general ring circuits in new homes.

NO

YOU

HAVE

NOT

So, I would assume a mixture of the two (most free under floors) would be around 25A per 2.5mm cable.

No - you have to consider the worst case point.

That gives a theoretical maximum of 50A on the ring.

No it doesn't.

 

[johnsville]

NO YOU HAVE NOT

I have. It may have been wrong. Probably was. It was in a brand new house I lived in for 18 months. All the houses around were like that.

 

[JohnD]

Or maybe you looked at an MCB that was supplying a 6mm radial, and didn't carry out tests to find out if it was a ring (this is much more likely)

 

[johnsville]

Or maybe you looked at an MCB that was supplying a 6mm radial, and didn't carry out tests to find out if it was a ring (this is much more likely)

Probably. I never took covers off and looked.

 

[bernardgreen]

NO YOU HAVE NOT

I have. It may have been wrong. Probably was. It was in a brand new house I lived in for 18 months. All the houses around were like that.

Just because it was a new house does not mean it was correct.

Look at this thread for incorrect and very dangerous electrical work in a new house.

//www.diynot.com/forums/viewtopic.php?p=1929065#1929065

 

[ban-all-sheds]

I am just musing. I see there is capacity left in the regs for safety reasons. The over actually draws under 16A.

THAT

OVEN

IS

TOO

BIG

TO

GO

ON

A

RING

FINAL

 

[ban-all-sheds]

NO YOU HAVE NOT

I have.

Go away.

 

[holmslaw]

NO YOU HAVE NOT

I have.

Go away.

 

[johnsville]

It is electrical forum always full of nutters? A conference load here.

 

[JohnD]

just one.

 

[bernardgreen]

It is electrical forum always full of nutters? A conference load here.

you need to learn to accept advice. While some of the advice provided here may be said in an agressive way it often happens because, like you, the person seeking advice only wants to hear what he or she wants to hear.

It is very frustrating for experienced people when they give up their time to try and help to be told "thanks but I am going to ignore your advice because it is not what I want to hear"

Hospital A&E have nutters delivered by ambulances when the DIY work they did without advice goes wrong. Sometimes it isn't the DIY person who is injured by his or her un-informed actions.

 

[johnsville]

It is electrical forum always full of nutters? A conference load here.

you need to learn to accept advice. While some of the advice provided here may be said in an agressive way it often happens because, like you, the person seeking advice only wants to hear what he or she wants to hear.

Nonsense! I asked some Qs and got answers. I wasn't sure if they were correct and bounce things back. One stated to me that a CU cannot be taken off a ring. But garage CUs are taken off rings - this is apart from my original query. This leads me to believe something may be misinterpreted, or they are just telling people to do it the way "they" always have done it. I see ugly fused spurs over kitchen worktops everywhere. I believe these are not mandatory in the BS. But we see these ugly switches all over because they always do it that way.

It is very frustrating for experienced people when they give up their time to try and help to be told "thanks but I am going to ignore your advice because it is not what I want to hear"

It is frustrating for experienced engineers like myself to communicate with attitude. In real life I would have no time of day for such people and they would get some sharp words immediately and be ignored after. But they can hide behind a keyboard here.

BTW, I have not bought an oven yet. SWMBO wanted a Miele.