4mm T&E for ring circuit

[steptoe]

Do you not have two cables at each outlet and all around circuit so that is up to 54 amp capacity?

no, its not parallel conductors

 

[a1spark]

You didn't mention it specifically.

Did I need to Volti ?

I stated : Does your method of installation require it...rating factors etc ? Would you not agree thermal insulation factors fall within this category ?

 

[ianmacd]

Did I need to Volti ? I stated : Does your method of installation require it...rating factors etc ? Would you not agree thermal insulation factors fall within this category ?

Seems clear enough to me.

 

[sanny]

Quote:

Originally Posted by steptoe View Post

a RFC consists of a cable (2.5) that can only carry 27a at most being protected by a 32a protective device (usually)

where does this little nugget of information come from?

The total load splits down each leg of the ring meaning that no one leg will ever take the full load so even when the breaker is near its limit the 2.5 mm cables are well within theirs!

sorry Steptoe thought this was common knowledge!

 

[kme]

The total load splits down each leg of the ring meaning that no one leg will ever take the full load so even when the breaker is near its limit the 2.5 mm cables are well within theirs!

sorry Steptoe thought this was common knowledge!

Did you now?

It may be common, incorrect knowledge, as this isn`t the first time that has been said - but I`m afraid you are wrong.

KME

 

[Voltimax]

Did I need to Volti ? I stated : Does your method of installation require it...rating factors etc ? Would you not agree thermal insulation factors fall within this category ?

I wouldn't disagree with that, but all I said was you didn't specifically mention that factor and you didn't, hence the reason Sidewinder maybe missed it.

 

[sanny]

oh i thought that current took the path of least resistance so depending on where on the ring it was plugged in determined which leg it came back on! im sure you'll correct me if im wrong though! lol

 

[steptoe]

oh i thought that current took the path of least resistance so depending on where on the ring it was plugged in determined which leg it came back on! im sure you'll correct me if im wrong though! lol

yes, the path of least resistance will usually be the shortest path(though not always,) therefore you could in theory have 2X13A loads plugged into the first double socket on the ring, shortest route/least resistance will be via the one leg of the ring straight back to the CU....... = 26A before you apply any other load, plus the fact 27A capacity is under ideal conditions.

of course, none of this is taking into account a fault/diy Bob and the broken ring scenario.

 

[sanny]

if you have one flexed appliance in your house that draws 13 amps i'd be very suprised never mind two!

 

[ianmacd]

my 3.3kw tranny may well do (no not Sandra).

 

[sanny]

my 3.3kw tranny may well do (no not Sandra).

How is Sandra?

 

[ianmacd]

How is Sandra?

Looks like he was on earlier. Maybe getting an early night.

 

[kme]

First:

The total load splits down each leg of the ring meaning that no one leg will ever take the full load so even when the breaker is near its limit the 2.5 mm cables are well within theirs!

sorry Steptoe thought this was common knowledge!

Wet FishThen:

oh i thought that current took the path of least resistance so depending on where on the ring it was plugged in determined which leg it came back on! im sure you'll correct me if im wrong though! lol

Wet FishWet Fisherm.......I`m confused now!

yes, the path of least resistance will usually be the shortest path(though not always,) therefore you could in theory have 2X13A loads plugged into the first double socket on the ring, shortest route/least resistance will be via the one leg of the ring straight back to the CU....... = 26A before you apply any other load, plus the fact 27A capacity is under ideal conditions.of course, none of this is taking into account a fault/diy Bob and the broken ring scenario.

:Applaud :Applaud:Applaud:Applaud:Applaudopcorn

 

[a1spark]

I wouldn't disagree with that, but all I said was you didn't specifically mention that factor and you didn't, hence the reason Sidewinder maybe missed it.

Hi Volti. by virtue of the fact that I didnt mention any particular Rating Factor; must by defenition mean that I was referring to the requirement to consider All of them, that of course includes Thermal.

Dont want to make an issue of it and ruin the thread so thanks for your view and your proxy views on Sidewinders behalf

 

[PC Electrics]

In a ring circuit the current supplying a socket outlet is split in inverse proportion to the resistance ratio of the two legs.

So, if the socket is half way round, then the current flows 50% along each leg.

If the socket is one third the way round the ring, one third of the current flows along the longer leg and two thirds along the shorter leg.

In a ring composed of entirely one size of cable, the ratio of resistance of two legs is also the same as the ratio of the lengths of the legs.

See here:

http://www.talk.electricianforum.co.uk/showthread.php?t=11467

 

[Sidewinder]

Peeps I've not been able to be around for a few days sorry, have a lot on over the next few months so may be a bit sparse.

a1, I rarely run cable through insulation, I was skimming the thread rather then reading it correctly!

Volti you were correct.

IF I am putting in a run of cable I will always undertake a full calc of all values prior to install unless it is a SERIOUSLY simple short run.