Please can someone tell me, is comparing 4mm and 2.5mm cable the same as comparing a chainsaw and a blender?

[ebee]

I'm not sure it's quite that 'easy' - where did that first egg come from?

Kind Regards, John

A Lizard, Just ask Charly Darwin , he knows all about it. Lizards evolved into chickens so a Lizard laid an egg and a chicken hatched out - simple

 

[bernardgreen]

A Lizard

More like a Chickard or a Lizhen, ,

 

[JohnW2]

...clearly ebee's answer was to a different interpretation of the question... I assume you missed this, or you would not have responded to his answer as you did.

Maybe. If he was talking about the life cycle of an individual chicken (or an individual of any other species which starts life as an egg), he was obviously right - that would be similar to asking "What came first, a child or an adult?".

However, I would suggest that is not what vis usually meant by the 'chicken and egg' question. We would normally describe (only) an egg produced by a chicken as "a chicken egg" but, since we are dealing with arbitrary definitions, we are here talking about a chicken which grew from an egg produced by something not regarded (by arbitrary definition) as a chicken (hence not a "chicken egg"). Hence, in that sense, the first chicken did not come from a "chicken egg".

As I said, like many things discussed in this forum, seeming really just a matter of (arbitrary) semantics./terminology.

Kind Regards, John

 

[JohnW2]

A Lizard, Just ask Charly Darwin , he knows all about it. Lizards evolved into chickens so a Lizard laid an egg and a chicken hatched out - simple

... but, of course, in reality it's not (at least, extremely rarely) like that. The first chicken almost certainly did not grow out of an egg produced by a lizard but, rather, from something that you and I (and probably most 'experts') could not distinguish from a chicken, and was only not 'officially' regarded as a chicken because of an arbitrary definition.

Evolution is generally a (extremely gradual) continuum, not 'giant jumps', even though a few people (like Richard Dawkins) might disagree!

Kind Regards, John

 

[ebee]

I was jokingly giving a quick answer John, not as eloquent as that Victor Russian guy who used to be the honorary Life President of Mensa. He gave a detailed explanation just as he did to the question "how long is a piece of string". He used to hurl back and forth "Kickself Questions" with Clive Sinclair, one good example is "What is the most difficult question in the world to answer?"

 

[JohnW2]

I was jokingly giving a quick answer John ...

Yes, I realise that, but my point remains.

Evolution is generally so incredibly slow/gradual that we really are down to the totally arbitrary question of when we regard an egg that grew into a chicken being produced by something that wasn't a chicken.

The question of how the first-ever 'egg' (of any sort) came into being is perhaps a more taxing, and more fundamental, one - given that it is hard to envisage any 'gradually changing intermediate steps' between a world in which there were no eggs and a world in which there was an egg. Maybe we have to take more notice of Dawkins

Kind Regards, John

 

[PotatoSoup]

Pragmatically, I agree.

However, a similar argument would probably say that it is exceedingly unlikely that, in a standard domestic setting, a 2.5mm² (or maybe even 1.5 mm²) radial protected by a 32A (or higher) OPD would result in any harm.

Returning to the OP, the difference between 32A and 40A (assuming Method C) is pretty trivial.

Kind Regards, John

Hi JohnW2,

Sorry, I'm being a bit thick I think - what do you mean by "any harm", please?

 

[PotatoSoup]

Hiya,


Again, some of this went over my head but I think I've understood the most important points for my situation:


The suggested choices are:


2.5mm radials @20A

2.5mm ring @35A

4mm radials @25A

4mm radials @35A


No-one is advocating for 2.5mm @20A in the kitchen.


Opinion is split over 'which is better': rings or radials.


There is no difference in safety between 4mm and 2.5mm cables in terms of fire and shock hazards.


4mm cable is more expensive to buy.


Radial circuits have the advantage that a fault on the circuit will be easier to spot.


I would need more radials than ring finals to wire the property. I think I'd need, or at least be happy with, 3 radials (upstairs, kitchen and the rest of downstairs), instead of just the one ring final to do the lot. So I'd need to use one extra MCB for the sockets. The extra MCB would cost approximately another £4 but more importantly I would need to check that I won't have too many MCBs for the RCDs in the consumer unit.


A 2.5 radial @ 20A may be possible. This would save on the cost of the cable. This would probably be an ok size for the upstairs and downstairs, excluding the kitchen.


There is not a lot of difference in the distance that 4mm radial and 2.5 rings can travel - 40m and 53m respectively.


No-one has mentioned the insulation being a problem so I'm going to assume that with normal domestic appliances any of the options are likely to be ok and, if not, my electrician will be able to tell me once he's had a look.


Perfect!! Thank you so much again, Everyone!! I really appreciate it

 

[EFLImpudence]

Ignoring larger cable being required because installed in places that restrict cooling:

2.5mm radials @20A

Could be 25A.

2.5mm ring @35A

32A - no 35A MCBs.

4mm radials @25A

No point; can be 32A.

4mm radials @35A

32A.

No-one is advocating for 2.5mm @20A in the kitchen.

Could be 25A.

Opinion is split over 'which is better': rings or radials.

As I said right at the beginning it depends on whether the actual route is a ring or straight line.

There is no difference in safety between 4mm and 2.5mm cables in terms of fire and shock hazards.

Of course not. No one said there was.

4mm cable is more expensive to buy.

So is 10mm² - but if that is what you require...

Radial circuits have the advantage that a fault on the circuit will be easier to spot.

Depends on the fault but no one considers that as a reason for choosing one or the other.

I would need more radials than ring finals to wire the property.

Not necessarily. People use rings because people use rings because they always have.

I think I'd need, or at least be happy with, 3 radials (upstairs, kitchen and the rest of downstairs), instead of just the one ring final to do the lot.

Ok?

So I'd need to use one extra MCB for the sockets. The extra MCB would cost approximately another £4 but more importantly I would need to check that I won't have too many MCBs for the RCDs in the consumer unit. A 2.5 radial @ 20A may be possible. This would save on the cost of the cable. This would probably be an ok size for the upstairs and downstairs, excluding the kitchen.

Now you are just 'saying things'.

There is not a lot of difference in the distance that 4mm radial and 2.5 rings can travel - 40m and 53m respectively.

But they can have spurs/branches so those lengths are meaningless.

No-one has mentioned the insulation being a problem so I'm going to assume that with normal domestic appliances any of the options are likely to be ok and, if not, my electrician will be able to tell me once he's had a look.

No, in insulation the cable needs to be larger or the MCB lower rated.
Don't run it in insulation.

Perfect!!

I wouldn't say that.

 

[FrodoOne]

Radial circuits have the advantage that a fault on the circuit will be easier to spot.


I would need more radials than ring finals to wire the property. I think I'd need, or at least be happy with, 3 radials (upstairs, kitchen and the rest of downstairs), instead of just the one ring final to do the lot. So I'd need to use one extra MCB for the sockets. The extra MCB would cost approximately another £4 but more importantly I would need to check that I won't have too many MCBs for the RCDs in the consumer unit.

And it would be much better if you used an RCBO on each "Radial" circuit, in lieu of an MCB, with a RCD "protecting" all of them., even if it does cost a little bit more.

Then, in the unlikely event of any "Earth Leakage" fault, you would know on which circuit the fault was - and have two other operative circuits while you were finding it.