Pfc / pscc

uksparks · Dec 5, 2014

Hi,

If you have a TNS supply, you would have a separate earth path by way of lead pipe or split concentric etc... true?

Ok, so if you have a PME / TMC-S supply, the earth connects to the neutral at the service head, yes... true?

Ok, so just out of interest, if you had an overhead TT thats now been converted into a PME, would you expect the PFC and PSCC readings to fluctuate if you keep taking the reading?

I just changed a board yesterday on this supply, and it was overhead TT, now PME, and im getting fluctuating readings anywhere from 0.22 to 0.28, ive checked my meter and checked again etc, and its all ok, but its fluctuating.

The only reason I say this is because, i also changed a board i dont know 6 months ago, i put it down as TNC-S / PME as thats exactly what I saw, the readings between PFC and PSCC were 0.1 ohms different. The NICEIC bloke said You are wrong, its not TNC-S and marked me down.

I said ok, well what is it then? He said its TNS on split concentric cable...ok fair point I said, he said that if its PME / TNC-S the readings will be exactly the same.

Now this one I have just done, its quite clean cut, theres two lines and one neutral, its NOT TNS, its not possible, but I am getting fluctuating readings.

Can anyone with a bit more knowledge enlighten me please.

I have connected the Earth into the left hand side as instructed by WPD as its been converted to PME and even has a sticker on it saying TNC-S / PME.

telectrix · Dec 5, 2014

have you checked to see if there's a link from N to the earth terminal?

uksparks · Dec 5, 2014

No I have not physically checked but can confirm there is 230v between line and earth and line and neutral.

uksparks · Dec 5, 2014

The new tails are approx 1.2m long, have checked it all 10x. The head was only changed a couple of days ago. Like I say it used to have a stake.

ruston · Dec 5, 2014

Tell him to mark down the DNO lol , it's marked up on the sticker.

Re read post , only read to bottom of your pic , but still it's marked up, did he see that.

uksparks · Dec 5, 2014

telectrix said:
have you checked to see if there's a link from N to the earth terminal?

I I can only assume there is due to getting 230v line to Earth

telectrix · Dec 5, 2014

perhaps DNO have a dodgy stake. have to ask joan of arc or hungry horse pub fo better info.

Scotford14 · Dec 5, 2014

Which readings are fluctuating? L-E Fault current or L-N short circuit current?

Guest77 · Dec 5, 2014

Have you tested between neutral and earth chuckle.

uksparks · Dec 5, 2014

MDJ said:
Have you tested between neutral and earth chuckle.

Yes it was zero volts

Guest77 · Dec 5, 2014

uksparks said:
Yes it was zero volts

Yes but was there continuity?

uksparks · Dec 5, 2014

Scotford14 said:
Which readings are fluctuating? L-E Fault current or L-N short circuit current?

I'm going back Tuesday so can say exactly but I think the LN was 0.28 and LE was 0.22 or 0.23 I think but when I tested both a couple of times and both figures were within 0.1 each time as in each figure goes up or down a peg.

uksparks · Dec 5, 2014

MDJ said:
Yes but was there continuity?

I can only say I didn't check if there was continuity but surely the fact that I've got 230v line to earth would that not suggest there's continuity?

uksparks · Dec 5, 2014

If my memory serves me correctly it was 909A LE and 855A LN, but may be wrong.

Guest77 · Dec 5, 2014

Dunno mate I wasn't there, if there is one cable coming into the neutral terminal and you confirmed continuity to the earth side of the cut out then thats the evidence you need to confirm it is indeed linked.