Max floor area of a ring main?

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Crosswire

I always thought that you were allowed "unlimited socket outlets within 100m Sq."

I got told today that if the floor area was above 75m Sq it required an addittonal ring and this was the "new Regs" .

Is this correct?
 
BG will tell him it's dangerous and needs replacing, before putting the socket tester away.
 
is this helpful.. 75sq.m. = bullsh!te. IMO.
 
Just to be helpful - nothing has changed with 'historical' rec's - but that has been frowned upon by anyone who is familiar with modern demands on a ring. I'ts not rocket science to know that as telectrix says, it's bull. Use initiative and calcs.
 
Hi Crosswire
As you can probably tell, the general consensus here is that the info you've been given is bull poo.
is there a job you're on with more than said floor space? also, who told you this duff info?
 
terminator said:
Just to be helpful - nothing has changed with 'historical' rec's - but that has been frowned upon by anyone who is familiar with modern demands on a ring. I'ts not rocket science to know that as telectrix says, it's bull. Use initiative and calcs.
Click to expand...

Thanks for that, I though so but wanted confirmation
 
dan86 said:
Hi Crosswire
As you can probably tell, the general consensus here is that the info you've been given is bull poo.
is there a job you're on with more than said floor space? also, who told you this duff info?
Click to expand...

It was another sparks on the job who is putting two general rings into a 3 bed flat that has atotal of 12 double sockets, on the basis that the floor area is 84 sq meters. (also kitchen ring, so three in total)
 
Crosswire said:
I always thought that you were allowed "unlimited socket outlets within 100m Sq."

I got told today that if the floor area was above 75m Sq it required an addittonal ring and this was the "new Regs" .

Is this correct?
Click to expand...

There used to be guidelines many moons ago, but i cant remember what they were, and they are irrelevant now anyway.
When you construct a ring (or any other circuit), you need to consider the loading, so if you were to install a ring into 4 bedrooms, and put 4 twin outlets in each room, and SFCU for a boiler or whatever, you wont have problem with loading, no matter how many tellys, laptops etc etc gets plugged in, you will not exceed the cable rating. But put a kitchen, utility room, garage on one circuit with unlimited outlets than you may encounter problems.

It all comes down to using a bit of common sense, and looking at the info available to you. If you look in the electricians guide to the building regs, there are guidelines as to how many outlets you should provide in each location, but they are only guidelines. You need to consider inconvenience in the event of a fault, so would it be a good idea to shove a 125m ring in? i doubt it, cos all the sockets might go off at once. You are correct in your assumption that you can have unlimited sockets on a ring, you can on a radial as well, but it all comes down to common sense. You can also spur from each unlimited socket once. When you design and construct any circuit, you need to ensure compliance to the regs, so think about Zs values and volt drop when calculating the length.

Cheers..........Howard
 
SirKit Breaker said:
There used to be guidelines many moons ago, but i cant remember what they were, and they are irrelevant now anyway.
When you construct a ring (or any other circuit), you need to consider the loading, so if you were to install a ring into 4 bedrooms, and put 4 twin outlets in each room, and SFCU for a boiler or whatever, you wont have problem with loading, no matter how many tellys, laptops etc etc gets plugged in, you will not exceed the cable rating. But put a kitchen, utility room, garage on one circuit with unlimited outlets than you may encounter problems.

It all comes down to using a bit of common sense, and looking at the info available to you. If you look in the electricians guide to the building regs, there are guidelines as to how many outlets you should provide in each location, but they are only guidelines. You need to consider inconvenience in the event of a fault, so would it be a good idea to shove a 125m ring in? i doubt it, cos all the sockets might go off at once. You are correct in your assumption that you can have unlimited sockets on a ring, you can on a radial as well, but it all comes down to common sense. You can also spur from each unlimited socket once. When you design and construct any circuit, you need to ensure compliance to the regs, so think about Zs values and volt drop when calculating the length.

Cheers..........Howard
Click to expand...

I agree with everything you have said, except for unlimited sockets on a radial circuit.
 
How standards have dropped!!, any experienced sparky I hope would not wire 12 s/o 0n 20 amp radial on 2.5mm cable.so you would say that's good practice then?
 
7029 dave said:
How standards have dropped!!, any experienced sparky I hope would not wire 12 s/o 0n 20 amp radial on 2.5mm cable.so you would say that's good practice then?
Click to expand...

yeah ?
well where did you get your numbers from ?
only 2 on a radial ? dont be daft.
seeing as the circuit device will prevent cable overload there is no maximum.
 
What's happening this evening, it must be the high pollen count. Some of these posts this evening are bordering insanity, why don't we just prevent the customer from using electricity just incase they alter something.

Give it a break, work to the regs and let the rest of the world go by.
 
Crosswire said:
I always thought that you were allowed "unlimited socket outlets within 100m Sq."

I got told today that if the floor area was above 75m Sq it required an addittonal ring and this was the "new Regs" .

Is this correct?
Click to expand...

if you have a look in onsite guide (amendment 1)

100m is the recomended max length for a 2.5 ring feeding sockets.

also mentions 50m for lights if i remember correctly, havent used onsite guide for a while
 
Rumour has it that the next BS7671 recommends that socket outlets be wired in 16mm T&E, be protected by a 6A breaker and the total number of SO's be limited to 0!
 
Surely if you only put 2 SO on a radial with a 20a breaker, there is FAR more likely hood of mr DIY adding sockets thus creating the circuit you fear so much, oh and he can also change the breaker to a 63a so why ain't you wiring in 16mm ' just in case'
 
Rampantchilli said:
Surely if you only put 2 SO on a radial with a 20a breaker, there is FAR more likely hood of mr DIY adding sockets thus creating the circuit you fear so much, oh and he can also change the breaker to a 63a so why ain't you wiring in 16mm ' just in case'
Click to expand...

Theres nothing stopping any numpty changing a breaker so that's a non starter - you can't legislate for the idiots, nor can you be held responsible for DIY antics later.
 
Last edited by a moderator:
shanky887614 said:
if you have a look in onsite guide (amendment 1)

100m is the recomended max length for a 2.5 ring feeding sockets.

also mentions 50m for lights if i remember correctly, havent used onsite guide for a while
Click to expand...

Okay guys, we need to put this one to bed. It's not "100m is the max length for a 2.5 ring feeding sockets." It's Maximum FLOOR AREA per 100 square metres. In the BGB they clearly state that "Historically, a limit of 100 square metres has been adopted". This is where the "ring final circuit starts and finishes at the distribution board, where it is connected to a 30A or 32A overcurrent protective device".

It is clearly a recommendation (historical). 433.1.103.
This can be achieved by:
(i) locating so's to provide reasonable sharing of the load around the ring.
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit.
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit.
(iv) taking account of the total floor area being served. (historically , a limit of 100m squared).

And it's not 50m length for lights - It's, for a Radial final circuit with a 20A protective device in 2.5mm (historically the floor area served is limited to 50m squared)

And for a Radial final circuit with a 30A or 32A protective device in 4mm (historically the floor area served has been limited to 75m squared.

I probably muddied the waters with my tongue in cheek comment that "mr diy would come along and uprate the breaker" This was meant as a throw-away quip - but obviously some peeps have taken it as verbatim. For that I apologise. I'll be more careful in future with my attempts at comedy.

I ought to add that the above quoted Regs are not aimed at the many regulars on here who are familiar with them - But those who may not have updated may find them helpful.

Ok, I'll put my tin hat on.
 

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