Ring final circuit Zs.

[Iona222]

Can you get the zs by using a earth loop impedance tester. I was taught if there's 2 rings circuits, you can do r1,r2, rn /4 on 1

On the other ring you can plug in the earth loop impedance tester and measure the zs. If you do it that way you must write in the observations you measured.

Have I been taught right?

 

[telectrix]

Can you get the zs by using a earth loop impedance tester. I was taught if there's 2 rings circuits, you can do r1,r2, rn /4 on 1

On the other ring you can plug in the earth loop impedance tester and measure the zs. If you do it that way you must write in the observations you measured.

Have I been taught right?

2 methods.
the 1st one you mentioned is by calculation... (r1+r2)/4 = R1+R2 and Zs = Ze+ (R1+R2). this is generally for initial verification and eliminates live testing.

2nd method is more accurate as it is a direct measurement and takes into account parallel paths such as bonding etc..

Both should be done IMO and the readings entered on the EIC.

 

[sinewove]

Can you get the zs by using a earth loop impedance tester. I was taught if there's 2 rings circuits, you can do r1,r2, rn /4 on 1

On the other ring you can plug in the earth loop impedance tester and measure the zs. If you do it that way you must write in the observations you measured.

⁰

 

[telectrix]

missing comment....got to be a C2.

 

[Dustydazzler]

Measuring all your little r readings is very useful because it A) verifies you actually have a ringadingding , and B) you can use these results later to calc your R1 R2 value.

once the circuit is energised you can plug in your efli tester to get your actual Zs reading

you should recorded all your values on the test sheet

 

[Lister1987]

As Tel says above; calculate then testing and compare.

Any idiot can press a button and wrote down a number, the skill comes in understanding the result, why/if the reading differs from the calculation and so on.

I don't know about everyone here but I like to know I should be getting, otherwise it's just ink on a page and has little meaning, bar filling box.

I had this same argument in college with the lecturer; I asked why are we not bring taught best practice, why they didn't find it necessary to go above the minimum requirement and just why they aren't challenging the ethos from the exam board of just doing the minimum.

 

[pc1966]

One thing I like about the RFC is you can verify it at the CU end with your r1,r2,rn readings (spurs excluded, obviously). During installation the figure-of-eight test allows very good checking of the condition/quality of connections to every sockets as any that differ by any significant amount are either on a spur or duff.

Of course if you have just installed a radial and know the end socket then you can achieve most of the same by checking against your calculations R1+R2 (to compute Zs), Rn+R2 and R1+Rn (to verify L & N are very similar and E is in the expected ratio for T&E).

When people complain the RFC testing is "more complicated" than a radial they often overlook the fact it offers very comprehensive fault coverage and they are usually skipping the neutral verification, etc, of a radial to the same degree.

Measuring Zs at the socket is easy and gives you the final check, but not as precise a measurement and I find the no-trip readings of Zs on my MFT are a bit variable (OK, maybe I should have got a Megger...).