0.00 ohms r1+r2 on radial circuit?

[Newbie90]

Hi all,

I've tested several radial circuits and only getting 0.00 ohms on the r+r2 test (zero'd leads)

2 of the radials only supplies one socket each and are approx. 3 metres in total length. (zs 0.25 and 0.21)
Another radial only supplies one socket and is appox. 5m in length. (zs 0.35)
The final radial supplies 2 sockets and approx. 7m in total length. (zs 0.53)

Are the readings due to the length of the run or could it be the batteries need changing on my Fluke Multifunction (even though no battery warning)

Thanks

 

[Plonker 3]

Have you removed the link and carried the same to test?

 

[telectrix]

3m of 2.5/1.5 will have a R1+R2 of 0.06. probably too low for your meter's resolution. try witout nulling the leads, then subtract the lead resistance from the measurement.

 

[Pete999]

Do you have a low ohms scale on your MFT?

 

[Newbie90]

Thanks for the quick replies.

The Fluke Multifunction is auto ranging for the continuity tests and according to their website, on the 20 ohms scale for continuity testing it's resolution is 0.01 ohms.

So I would of thought it could read as little as 0.01 ohms.

I've heard they produce funny readings when they need new batteries but I've had no warning.

 

[Pete999]

Just to prove your MFT how about fitting some replacement batteries, and see if that make any difference

 

[telectrix]

and you've been a member long enough that you should know there's no such thing as r1+r2 on a radial . :6:

 

[Silly Sausage]

Or try your instrument on some lengths of spare cable and see what you get.
Compare your readings against the theoretical values in the back of the OSG.


Ha, missed that one Tel!

 

[Newbie90]

and you've been a member long enough that you should know there's no such thing as r1+r2 on a radial . :6:

What do you mean?

You do an r1+r2 test on every circuit.

 

[telectrix]

rubbish. r1,rN, and r2 are end/end resistances of a RFC.

 

[Hobsoni]

telectrix is being sarcastic

 

[Newbie90]

rubbish. r1,rN, and r2 are end/end resistances of a RFC.

Agreed, but when testing the continuity of cpc's by linking out line and earth and testing at each point, the measurement obtained is r1+r2.

 

[brucelee]

R1+R2 is what your looking for

 

[Plonker 3]

That's R1+R2

 

[Pete999]

and you've been a member long enough that you should know there's no such thing as r1+r2 on a radial . :6:

Missed that one mate teach me to note the diff in r1+r2 and R1+R2 wont it?

 

[Hobsoni]

Although technically its R1+R2 for your radial circuits. Whereas you record r1+r2 around your RFC with the highest value being classed as R1+R2. Is this a play on the capital 'R' telectrix?

 

[Plonker 3]

R1+R2 and r1+r2 on a RFC are two different values.

 

[Silly Sausage]

Although technically its R1+R2 for your radial circuits. Whereas you record r1+r2 around your RFC with the highest value being classed as R1+R2. Is this a play on the capital 'R' telectrix?

Don't forget your divide by 4 now!

 

[Hobsoni]

Thanks gents. Bring on the onslaught

 

[Silly Sausage]

I'm off to dig out my GN3 so I don't make a balls up!

 

[Plonker 3]

Quick quiz for you

A RFC has continuity values of r1=0.4 ohms, rn=0.4 ohms and r2=0.4 ohms

What is r1+r2?
What is R1+R2?

 

[Geoffsd]

Why does RFC stand for Ring FC and not Radial FC?

 

[telectrix]

Although technically its R1+R2 for your radial circuits. Whereas you record r1+r2 around your RFC with the highest value being classed as R1+R2. Is this a play on the capital 'R' telectrix?

no. with a rfc, you measure end/end of each conductor. these values are denoted by lower case r. when you cross connect on a RFC, or just connect L-E on a radial, you then measure R1+R2. ( denoted by upper case R ).

 

[Hobsoni]

Quick quiz for you

A RFC has continuity values of r1=0.4 ohms, rn=0.4 ohms and r2=0.4 ohms

What is r1+r2?
What is R1+R2?

Ok. Here it goes. I would take r1 (0.4) and r2 (0.4) add them together (0.8) and then divide by 4 (=0.2). This would be the reading I would expect for all outlets within the ring main. So I test and I test, and test some more jotting down all my values as r1+r2. As I test, I notice I have what I think is a spur as the value is greatest and is actually 0.36ohms. This value being the greatest of the circuit is recorded as my R1+R2 for the ring circuit. PS: with the values you gave, I'm guessing the cables used are singles. Did I Pass?

 

[Newbie90]

no. with a rfc, you measure end/end of each conductor. these values are denoted by lower case r. when you cross connect on a RFC, or just connect L-E on a radial, you then measure R1+R2. ( denoted by upper case R ).

I get it now haha :willy_nilly:

 

[Silly Sausage]

Why does RFC stand for Ring FC and not Radial FC?

Because higher beings than us say so!

 

[telectrix]

it also stands for Rugby Football Club, but i wouldn't like to attempt an IR test on a prop forward.

 

[telectrix]

Ok. Here it goes. I would take r1 (0.4) and r2 (0.4) add them together (0.8) and then divide by 4 (=0.2). This would be the reading I would expect for all outlets within the ring main. So I test and I test, and test some more jotting down all my values as r1+r2. As I test, I notice I have what I think is a spur as the value is greatest and is actually 0.36ohms. This value being the greatest of the circuit is recorded as my R1+R2 for the ring circuit. PS: with the values you gave, I'm guessing the cables used are singles. Did I Pass?

yes, but cable could also be SWA with the armour earthed but not used as cpc. the cpc core is the same size as the L and N.

 

[Silly Sausage]

it also stands for Rugby Football Club, but i wouldn't like to attempt an IR test on a prop forward.

Don't you fancy testing your wind up Megger on MDJ's goolies?

 

[Hobsoni]

it also stands for Rugby Football Club, but i wouldn't like to attempt an IR test on a prop forward.

Not necessarily a prop forward, but you might have some luck probing a hooker