Continuity Assistance - Lighting Circuit with readings!

riveralt · Posted: Tue Mar 13, 2012 1:45 pm

dizz wrote:

Now I'm getting a bit hacked off - Continuity on the circuits, and finnaly started to attck the ring. Cross connect CPC and neutral at the CU and took a reading of 0.85 ohms. Checking for bridges, so cross connect both phase and neutral at CU, and go round the sockets, 0.21, 0.24, 1.74, 0.22, 1.55, ... and on one double socket I get a reading of 0.22, and on the same socket, over 1 ohm. Click the switches and the reading changes a bit, sometimes I can get it down to just over 0.2 ... it's all looking a bit problematic.

We have had this discussion before.....
If you are going to conduct tests do them properly in the proper order.
What where you end to end readings? r1 r2 rn.

Do the cross connect (figure of eight) readings equate to 1/4 r1+r2?
What radials do you have running off the ring final circuit - the end of which can give you higher readings.

dizz · Posted: Tue Mar 13, 2012 2:39 pm

Hi Riveralt - R1+R2 was 0.85 ohms as stated, now I'm moving on by cross connecting L1/N2 and L2/N1 at the CU, which is about 0.21, a quarter of the 0.85 I was getting!

HOWEVER, the pertinent "discussion" we had before though was when you said "BTW new switches are sometimes sticky and a few seconds flicking them on and off sometimes clears the cobwebs".

After doing what Holmslaw suggested by connecting the probes together and "wiggling" the wires, it revealed nothing, the reading was as solid as a rock - so I thought I'd flick the switches a number of times (and I mean a number - it took about 40-50 switches to "clear the cobwebs"), and now I get readings between 0.19 and 0.23 on every socket.

I guess that the manufacturing process might mean that some sort of coating gets on the metal which adds resistance, and the constant flicking of the switches wears that away??!!, until you get a perfect connection??!!

PS - only have two "small" spurs from the ring, which increased the reading to 0.25/0.26

ADDED - Sorry meant R1 + R2 = 0.85/4 - no haven't done r1, r2, rn separately!! oops

RF Lighting · Posted: Tue Mar 13, 2012 8:31 pm

riveralt wrote:

We have had this discussion before.....
If you are going to conduct tests do them properly in the proper order.

17thman · Posted: Fri Mar 16, 2012 10:32 pm

dizz wrote:

Hi Riveralt - R1+R2 was 0.85 ohms as stated, now I'm moving on by cross connecting L1/N2 and L2/N1 at the CU, which is about 0.21, a quarter of the 0.85 I was getting!

R1 +R2 is the resistance of the line conductor(s) and cpc(s). if you have .85 ohms as a R1 + R2 on a ring final socket circuit then you really need to check your supply type as its its sqeeky bum time if you are measuring at non operational temperatures.

Secondly, if you are cross linking Line and Neutral and comnparing it with R1 + R2 without knowing r1 r2 and rn, what is it worth.

consider not correctly crossing L and E then the measurements wiill differ depending on where in the circuit you measure.

dizz · Posted: Mon Mar 19, 2012 8:39 am

Thanks 17thman - I was quoting R1 and R2 loosely - from my post, that was the reading of the L2-N1 reading from cross connect of L1-N2 at the board, so R1+R2 should be 1/4 of 0.85 ohms, so when I do the external loop I hope that it won't be "sqeeky bum time".

Regarding the Zs - I plan to measure the Zs for the ring and radial, as I have a plug, but for the other circuits I plan to just add the R1+R2 to the Ze - is that acceptable, and normal practice?

kevindgas · Posted: Mon Mar 19, 2012 8:49 am

@dizz, yes i've had a few issues with those double sockets and now don't buy them. buy from TLC now as although still cheap switches are slightly better quality and their cable is cheaper too!