PIR Test high Zs on 32 Amp RCBO

[Guest 004]

Hi people

I had an high Zs of 0.85 on a 32 Amp type C ring circuit, which was on an RCBO. My first thought was to give it a code 2 'requires improvement', and then change it to a type 'B' so it would conform. Then I thought it is on an 30mA RCBO, where the max Zs in theory can be 1667 ohms. Just asking what you guys would do and why.

 

[tony mc]

If no RCD protection then it would fail in the disconection time but as you say a RCD is now covering the cct so it has additional protection so IMO no code.

Is there any reason for the type C on the cct.

 

[Deleted member 9648]

All other tests being satisfactory I would not code it,the RCD will ensure disconnection times are met.

 

[Guest 004]

what about Phase to Neutral faults?

 

[Chr!s]

what about Phase to Neutral faults?

Seeing as its TNCS id advise checking thermal constraints, mcb might be a bit slow to disconnect LOL

 

[tony mc]

Is that not something different as the neutral is not part of the ZS loop.

On a line to neutral fault it would be the PSCC which would blow the MCB

 

[Guest 004]

Seeing as its TNCS id advise checking thermal constraints, mcb might be a bit slow to disconnect LOL

thanks Chr!s never thought of that. Seriously please guys

 

[Guest 004]

Is that not something different as the neutral is not part of the ZS loop.

On a line to neutral fault it would be the PSCC which would blow the MCB

dont know, thats why a I am asking

 

[Guest 004]

The impedance between P N is high also.

 

[Chr!s]

Is that not something different as the neutral is not part of the ZS loop.

CNE? or PEN?

On a line to neutral fault it would be the PSCC which would blow the MCB

Indeed, though if we have three conductors all the same csa Neutral and Earth connected at the link, if we have a high Zs then we could also assume a high L -N loop reading.

Ive seen A very similar thread somewhere else

 

[Amp David]

Could be loose connections somewhere then

 

[Guest 004]

everything is tight, circuit just a little too long for a type 'C' to work in time

 

[Chr!s]

Could be loose connections somewhere then

I think mrenigma may be referring to where the Ze is high, though it may be down to poor design or as David says a loose connection

 

[telectrix]

for what reason is it on a type C?. if no need for it, fit a type B.

 

[Guest 004]

No the Ze is good, 0.15 ohms