Final Circuits - Ring or Radial?

[OldskoolUpNorth]

I was speaking to an Electrical Engineering suit not too long ago,

He reckons that there's talk of Ring Final Circuits being done away with and the preference to install Radials only.

Anyone else heard this little gem.

Whats the general preference of everyone for the two systems????

Anyone already doing just Radials??


Ta,

 

[Guest55]

If rings are being phased out it will have to wait until the 18th regs then
They are of use in kitchens but i still prefer radials.

* Gets popcorn , could be a loooong thread lol.

 

[SW1970]

It's under the high integrity earthing section mainly used for IT where cumulative earth leakage is an issue
J

But can also be a problem in domestic with the amount of gadgets we plug in these days. A few PCs here and there, games units, LCD TVs, modern hifi, under desk home UPS units etc and it all adds up. Have seen 17mA on a domestic radial before. Does anyone actually check protective conductor currents on a routine basis other than when on a tripping RCD call out?

 

[Jimmy Boy]

But can also be a problem in domestic with the amount of gadgets we plug in these days. A few PCs here and there, games units, LCD TVs, modern hifi, under desk home UPS units etc and it all adds up. Have seen 17mA on a domestic radial before. Does anyone actually check protective conductor currents on a routine basis other than when on a tripping RCD call out?

Don't suppose they do, a good point tho, although I would say if you had 17mA on one Radial I would want to know what the hell was that leaky. I did look in to buying a clamp meter for this purpose as I am unsure if my normal clamp will measure low values like that.
J

 

[SW1970]

Not all clamp meters do; need one that can measure mA. Although can put a multimeter in series if able to safely disconnect earth for the test and able to turn all the gadgets on.

 

[Jimmy Boy]

Not all clamp meters do; need one that can measure mA. Although can put a multimeter in series if able to safely disconnect earth for the test and able to turn all the gadgets on.

Is that safe ha ha ha ! I'm off to look at my clamp
J

 

[Jimmy Boy]

Well I have the fluke 321, specs say for Amps 0-400.00 it has a 3 digit display, just out of interest I put it around a tail and pulling 11A put it on the main E get a reading of 00.6 switch the kettle on goes up to 02.1 is this right ? or is the meter out of range ? how can it register 400A if I only have two digits a decimal point then one digit ?
TNCS PME supply
J

 

[SW1970]

It can't measure mA. This is the spec from the fluke website:

Range: 0-400A Resolution 0.1A
Range 0-40A (Fluke 322 only) Resolution 0.01A

A spec for a mA meter will be something like a 3mA range with resolution of 0.01mA and 30mA with resolution of 0.01mA, etc.

Not sure what's going on with your readings there.

 

[PC Electrics]

I generally prefer radials, but the rfc has its uses. For example, i am currently wiring a small work area for a company. The heavy duty kit has its own 3ph supply or runs on air. But they need sockets to plug in some lights and over a small bench area. I would normally have put the sockets on a radial, especially as the area is only the size of a single garage, however I cannot avoid running some cable in insulation, method 103. This reduces 2.5 to 17A. So I cannot put in a 20A radial, so instead I'm putting in a 20A rfc (I would have made it 25A but couldn't get a 25A RCBO without special ordering it).

In domestic and commercial the rfc also has the advantage of "reach". With it's substantially reduced volt drop compared to a radial and it's ability to share the load over two legs, an rfc can be installed in a largish area that might require several radials (IT considerations aside). Or it can be used to reach third floor bedrooms involving long initial runs.

Rfcs are also useful for high integrity earthing, as you don't need to install an extra g/y return cpc as you do with radials.

Don't forget that an rfc does not have to be 32A/2.5mm. Other ocpd/cable combinations are available!

Viva la rfc! (even though I prefer radials)

 

[Jimmy Boy]

It can't measure mA. This is the spec from the fluke website:

Range: 0-400A Resolution 0.1A
Range 0-40A (Fluke 322 only) Resolution 0.01A

A spec for a mA meter will be something like a 3mA range with resolution of 0.01mA and 30mA with resolution of 0.01mA, etc.

Not sure what's going on with your readings there.

Thanks buddy I couldn't quite work out the zero-400 zero is just that isn't it ?

Steve

 

[rich.250]

My Megger earth
Leakage clamp has found me leakage causes double time
Highly recommended!!