Ring cct ratings?

[Nicky Tesla]

Hello, i was on a job the other day when I spotted a seemingly professionally installed CU. It had a NICIEC sticker on it with the cct list with the obvious details such as lighting, conducter size etc, but it never had any columns for any test results such as r1+r2, Zs etc. It did have though was a column for installation method and this was put down as 101 for every cct.

Now not familiar yet with the new method numbers i found out that 101 means installed in insulation in excess of 100mm in the loft, but the only ccts that went through the loft on this newly done rewire was for the upstairs lights, so that cannot be right anyway the others should have been at least a B.

When I was looking in my new OSG it puts 2.5 t&e on the 101 method down at 17A, so this was when i wanted to know if that meant that the cable should have been a 4mm ring cct. In my old yellow regs book the reg no:433-02-04 states " Such ring ccts are deemed to meet the requirements of regulation 433-02-01 if the current carrying capacity(Iz) of the cable is not less than 0.67 times the rated current or current setting of the protective device(In)"

This means that the cable would need to be at least 21A rated, making it require 4mm for the ring.

But I cannot find the above quote in the new regs since they have messed about with the system, so does it still exist or have things changed which now allows this?

 

[septiclecky]

Hello, i was on a job the other day when I spotted a seemingly professionally installed CU. It had a NICIEC sticker on it with the cct list with the obvious details such as lighting, conducter size etc, but it never had any columns for any test results such as r1+r2, Zs etc. It did have though was a column for installation method and this was put down as 101 for every cct.Now not familiar yet with the new method numbers i found out that 101 means installed in insulation in excess of 100mm in the loft, but the only ccts that went through the loft on this newly done rewire was for the upstairs lights, so that cannot be right anyway the others should have been at least a B.

When I was looking in my new OSG it puts 2.5 t&e on the 101 method down at 17A, so this was when i wanted to know if that meant that the cable should have been a 4mm ring cct. In my old yellow regs book the reg no:433-02-04 states " Such ring ccts are deemed to meet the requirements of regulation 433-02-01 if the current carrying capacity(Iz) of the cable is not less than 0.67 times the rated current or current setting of the protective device(In)"

This means that the cable would need to be at least 21A rated, making it require 4mm for the ring.

But I cannot find the above quote in the new regs since they have messed about with the system, so does it still exist or have things changed which now allows this?

You are forgetting that because it is a ring, in theory it is 2 x 2.5 in parallel thus each cable capable of carrying 17Amps each so 2 x17=34Amp

 

[Nicky Tesla]

Its ok ive found the answer on another forum.

The new regs now ignore the 0.67 but simply say the cable used needs to have a rating(individually) of at least 20A, so it did need to be a 4mm ring.

433.1.5

 

[SPECIAL LOCATION]

Hello, i was on a job the other day when I spotted a seemingly professionally installed CU. It had a NICIEC sticker on it with the cct list with the obvious details such as lighting, conducter size etc, but it never had any columns for any test results such as r1+r2, Zs etc. It did have though was a column for installation method and this was put down as 101 for every cct.Now not familiar yet with the new method numbers i found out that 101 means installed in insulation in excess of 100mm in the loft, but the only ccts that went through the loft on this newly done rewire was for the upstairs lights, so that cannot be right anyway the others should have been at least a B.

When I was looking in my new OSG it puts 2.5 t&e on the 101 method down at 17A, so this was when i wanted to know if that meant that the cable should have been a 4mm ring cct. In my old yellow regs book the reg no:433-02-04 states " Such ring ccts are deemed to meet the requirements of regulation 433-02-01 if the current carrying capacity(Iz) of the cable is not less than 0.67 times the rated current or current setting of the protective device(In)"This means that the cable would need to be at least 21A rated, making it require 4mm for the ring.

But I cannot find the above quote in the new regs since they have messed about with the system, so does it still exist or have things changed which now allows this?

As you say Nicky

'433-02-04' In the old yellow regs book.... (referring to coordination between conductor size & protective device and specifically ring circuits protected by 30A or 32A protective devices)

states "Such ring ccts are deemed to meet the requirements of regulation 433-02-01 if the current carrying capacity(Iz) of the cable is not less than 0.67 times the rated current or current setting of the protective device(In)"

{ SIDE NOTE: 433-02-01 is characteristics of protective device shall satisfy:-

(i) nominal current setting (In) not less than design current (Ib) and

(ii) nominal current setting not exceed lowest current capacity (Iz) of conductors, and

(iii) current (I2) causing effective operation of device not exceed 1.45x lowest current capacity (Iz) of any conductors }

So as you say yellow book suggests;

0.67x30A = 20.1A or

0.67x32A = 21.44A capacity.

In the Brown book

433-02-04 has been re-worded such that the 0.67 bit has been replaced with "current capacity (Iz) of cable is not less than 20A"

and 433-02-01 looks pretty much the same as yellow book.

In the new Red book an earlier paragraph 433-01 has been removed, such that the 433-02-xx stuff has shifted back a number range.

So 433-02-01 is now 433.1.1, which has the same as before plus some extra lines.

and your "433-02-04" is now 433.1.5 which is slightly re-worded from the brown book.. But still has the bit that 433.1.1 will be satisfied if current capacity of ring circuit cable not less than 20A (or words to that effect! )

HTH m8! :|

 

[SPECIAL LOCATION]

Its ok ive found the answer on another forum.The new regs now ignore the 0.67 but simply say the cable used needs to have a rating(individually) of at least 20A, so it did need to be a 4mm ring.

433.1.5

oh you beast!

I just been typin that up!

you didn't give me time to finish doing my kids taxi service

:|

Blushing:^O:^O:^OGuiness DrinkGuiness Drink

 

[Nicky Tesla]

Hi spesh ...dont your kids know whats more important , sort um out!

Anyway ive just also realised that the ratings are for 30 deg and the loft temperature will be considerably lower poss about 20 deg ( or will it? on a summers day)

 

[SPECIAL LOCATION]

Hi spesh ...dont your kids know whats more important , sort um out!Anyway ive just also realised that the ratings are for 30 deg and the loft temperature will be considerably lower poss about 20 deg ( or will it? on a summers day)

Summers Day???

that'll be water cooled system them!!

reckon you could stick 50A through!!!! ] :^O :^O:^O:^O:^O