Ring Circuiot

[GStueyXR]

stuey gonna do me a fav n phone IET with your calculations so they can rewrite the regs Id love to hear their reaction to a 40a ring on 1.5

Take a look at table 4D2A (p276) of bs7671.

Using Ref method C 1.5mm will safely pull 19.5A....

If you ring it, you effectively double it's CCC.

So, A ring circuit using 1.5mm protected by a 32A MCB is more than safe ( Ib<In<It ) (but does it comply?)

 

[mogga]

OSG Appendix 8 table8a Minimun csa for ring circuits a1 ring 32a 2.5mm max floor are 100m2

 

[GStueyXR]

I cannot find any regs stating 1.5 is unacceptable for a RF. Not good practice imo, but can anyone show me the regs to show it dosent comply?

Even with a 32A pull voltage drop is still <5% too.

Still shoddy though.

OP, why would you even consider altering the circuit ? Just pull some shiny new copper !

 

[martynb01132]

Had a look at said table but does not say wired as a ring. Sockets can be wired in 1.5mm but only spurred off a ring through a fuse spur and wired in a radial not a ring, does not comply.

 

[martynb01132]

BS7671 Appendix 15 page 362

 

[GStueyXR]

OSG Appendix 8 table8a Minimun csa for ring circuits a1 ring 32a 2.5mm max floor are 100m2

Got it... Nothing in 7671 tho, unless I am goin blind!

 

[GStueyXR]

Got it... Nothing in 7671 tho, unless I am goin blind!

LOL, seems I am goin blind!

 

[GStueyXR]

anyway... i was not condoning use of 1.5.. just stating it was safer in a ring than in radial.

 

[martynb01132]

Got it... Nothing in 7671 tho, unless I am goin blind!

Thing is if the BS7671 stated what a ring could not be wired in it would be a very very big book

 

[Guest123]

Take a look at table 4D2A (p276) of bs7671.

Using Ref method C 1.5mm will safely pull 19.5A....

If you ring it, you effectively double it's CCC. No you dont, not in CCC aspect.

So, A ring circuit using 1.5mm protected by a 32A MCB is more than safe ( Ib<In<It)Sorry mate but that bit is nonsense. (but does it comply?)

Wrong table Stuey.....flat T+E is table 4D5, P282.

Applying the correction factors a 1.5mm T+E at it's best (not clipped direct as it wont be) will just about take 16A.

In theory you can have a ring circuit of any size.....caravan parks for example, and the rule of thumb for sizing a cable to an OCPD is to mutiply the OCPD by 0.67 to give you the minimum CCC of the cable to be installed as the ring, i.e - 32 x 0.67 = 21.44A, well above the max for a 1.5.

This is how I arrived at 20A in my previous post, 20 x 0.67 = 13.4A, below the max for a 1.5. I personaly still would not do that though, and would ideally rip it all out and start again.

 

[eco-tech]

Gulp........... After reading all that im lost what to do now..............

What is the best action for it to be safe for a couple of weeks or so

1: Spilt the ring into 2 radials and put on 16amp breakers ?
2: Keep the ring and put on a 20 amp breaker ?

Just dont want a fire .................
2:

 

[Des 56]

As a ring circuit, it is at the best unconventional, at worst it is not permitted
The Brb may not state that,but it is not a standard circuit

The discussions over the current carrying capacity has not mentioned the cpc
This being 1.0mm would definitely make me decide to split the ring and 16amp the radials
You will need then to split the circuit where loading and circuit readings allow

 

[eco-tech]

Ok so it's 16 amp radials then ?

 

[GStueyXR]

As a ring circuit, it is at the best unconventional, at worst it is not permitted
The Brb may not state that,but it is not a standard circuit

The discussions over the current carrying capacity has not mentioned the cpc
This being 1.0mm would definitely make me decide to split the ring and 16amp the radials
You will need then to split the circuit where loading and circuit readings allow

But as a ring it has 2mm of cpc.... Pah, boring myself now.

Personally I would not touch the circuit until the customer agrees to rewiring it.