Maximum Number of PC Outlets According to BS

BS7671 places no limits on the number of socket outlets that can be added to a ring circuit.

BS7671 places a maximum floor area that a ring circuit can supply.

You are totally right about what you said.

I've already read what you said, but I was checking if it is stated in any other reference different than the Electricians Guide.

Thank you a lot.

What is the floor area limit for ring circuit i think it is adjusted as per 100w per outlet and voltage drop and other calcs.

regards

The total floor area is 100 m2 per ring circuit

This is correct.

This is incorrect.

then , What is correct ?

#4 is correct.

hello, Go back to the basic of electrical installation. What are your total maximum load in one ring? what is the appropriate wire size for that load? What is the size of the circuit breaker you used? In Short you need to consider the safety side of the system and your machine. Then you can tell the number of outlets you can install.

Regards,

erel

The total maximum load in 1 ring is 32A. The wire size for a ring is 2.5mm² twin-and-earth. The circuit breaker is 32A. All this is given in BS7671. And BS7671 doesn't care how many sockets are attached to the ring, so long as the floor area each ring services is 100m² or less. That's in BS7671 as well. So as long as the original poster follows BS7671, all will be well.

The regulation mentions floor area(50/100m2),wire size(2.5/4mm2),MCB(20/32A) for ring/radial/spur circuits.The Engineer based on his experience can decide the number of sockets in a circuit provided the total leakage current in that circuit do not exceed the tripping current(30mA) of the RCD.As wiring practice varies from nation to nation one should adapt to rules followed in that country.

4mm² twin-and-earth is not used in rings under BS7671 as 2.5mm² twin-and-earth is adequate for a 32A ring.

20A breakers are used for 2.5mm² twin-and-earth radials.

32A breakers are used with 4mm² twin-and-earth radials, though it can be difficult to get 2 x 4mm² conductors into the terminals of some fittings.

<...provided the total leakage current in that circuit do not exceed the tripping current(30mA) of the RCD...>

BS7671 does not contain an algorithm for working this out:

• If one had 25mA leakage in one ring and 25mA in another, would the 30mA leak trip in a split-load distribution unit support the load, or would it trip [rhetorical question]?

so the concept is absurd.

It is always advisable to load a circuit protected by a RCD to 50% of tripping current(30mA) of the device as computers and other electrical devices manufactured in some countries may have high leakage currents.When testing RCD it should not trip for 50% of its tripping current.Further in power distribution system of an installation there is a maximum allowable leakage current expressed as a (around 5%)percentage of the current rating of the main incoming CB.Some principles have been found appropriate by experience and not by any rules or regulations.

If the total leakage exceeds 30mA RCD should trip.

first of all

those people who have NOT read the 17th Ed IEE reg BS 7671, not worked with 17th Ed, not from the UK need not answer. Second read the regulations and the guide and remember that you can also add as many spur outlets as there are outlets in the ring main.

PW slack has given you the correct answers, so no need for further discussion.

for my Asian friends, no offence intended, but this is a very exact question requiring no generalisations, but a defined answer that only those with experiance and the qualification in the 17th Ed IEE Regs from the UK can answer.

The "guide to the wiring regulations" by Darrell Locke published by ECA says the total leakage current in circuits protected by a 30mA RCD should not exceed 25% of the rated tripping current(30mA)

its a guide, how many ring mains have you installed in the UK?

do you have a current qualification in the 17th Ed of the Elect Regs for the UK? Have you read the 17th Ed?

Being well read is not the same a being well practiced!