rapid reply please.

[amckay]

Just tested a bus shelter and am getting zs of 1.49.
Tns supply. 61009 rcbo 6A 30mA. Ze is .17
Ir tests all read >999Mohm.
Can anyone tell me if zs complies? Osg is in the office
Cheers

 

[amckay]

Oh and rcbo tests @ 42.6/1 & 20.3 /5

 

[malcolmsanford]

Yes 1667 for an RCBO

What size cable is it and approx length

 

[amckay]

Line conductors 1.5 bonding6mm.
Maybe just having a brain fart as were otrackered and jobs are timed couple that with holding in a turd....lol

Thanks very much

 

[malcolmsanford]

I know you are only a trainee but what as bonding got to do with it ..............

 

[telectrix]

Just tested a bus shelter and am getting zs of 1.49.
Tns supply. 61009 rcbo 6A 30mA. Ze is .17
Ir tests all read >999Mohm.
Can anyone tell me if zs complies? Osg is in the office
Cheers

ever heard of ohms law?

trip current for 6A RCBO (type B) is 30A.... (5 x In) . so

Zs Max = 230/30 = 7.667 oms ( without correction factor/s)


SIMPLESS....

 

[Leesparkykent]

ever heard of ohms law?

trip current for 6A RCBO (type B) is 30A.... (5 x In) . so

Zs Max = 230/30 = 7.667 oms ( without correction factor/s)


SIMPLESS....

Subtract 5% :53: Lol

 

[telectrix]

Subtract 5% :53: Lol

Smartarse. is that before or after the 20% in the osg?

 

[Leesparkykent]

Smartarse. is that before or after the 20% in the osg?

Either way will do :wink5:

 

[amckay]

Thanks for your help guys, tel I should have known better!! Thinking cap is on lol

 

[malcolmsanford]

If we use ohms law then the actual EFLI is 230/0.03 which is 7666 recurring. On a TN system where the maximum Ze would be 0.8 to achieve 7666 would be quite a challenge.

411.4.9 clearly tells us that we use table 41.5 when we are using an RCD to satisfy Regulation 411.3.2.2 which is the case here. So the Zs would be 1667.

 

[Leesparkykent]

1667ohms is a bit of a get out of jail free card for bad design on a TN system IMO :earmuffs:.