max zs over.

[KNIPEX]

hi guys, was doing a periodic today and a number of circuits were over max zs for a type c mcb what would you code that??

i was thinking a code 3 myself.

also a number of light fittings couldnt not be tested as they were the chandler type so ive noted this on the test sheet. do u see any issues with that??

thanks

 

[scotsparky]

If its over maqx Zs i would code 1 it as it means the Disconnection time isnt acheeved. double check with your time current curves. If its in a house of office you may get away with changing MCB to B type to sort out the problem.

As for Light take a ZS at the light switch and note what you did.

 

[Guest123]

Hi mate.

What earthing system did you have??

If it was TT was there an RCD present?? if so max is 1667ohms for 30mA lets not forget.

 

[electricAl]

I`d of thought code 1/2 for high Z`s, but not `requires further investigation`(3)

Wouldn`t argue with anyone putting a 1 for this, but i tend to reserve 1`s for items which present a danger without requiring a fault conditions to arise (ie Basic Protection)

For me it`d be a Code 2 as ADS would be required in the event of a fault.

 

[KNIPEX]

tncs mate with 30ma rcd upfront.

 

[scotsparky]

How high is the ZS? if its TH-C-S then it should be easy to reach max Zs Mind you it may be the lenght of run in which case consider your voplt drop. Code 3 it as you have an RCD for fault protection and your MCB will cover overload protect5ion.

 

[baldsparkies]

If the Zs is protected by an RCD ie 1667 ohms then your disconnection time in the event of an earth fault will be shown by your RCD x1 and x5 times readings which if good will cover your type C cus your gonna be under 40ms 0.4
Also if it satisfies disconnection time why code it, it complies.

 

[scotsparky]

I would code it as a 3 just incase its a dodgy earth causing high readins. no harm in having a look.

 

[professional]

Hi mate.

What earthing system did you have??

If it was TT was there an RCD present?? if so max is 1667ohms for 30mA lets not forget.

What about testing your sockets at 150mA?

 

[Guest123]

1533ohms

 

[baldsparkies]

I would code it as a 3 just incase its a dodgy earth causing high readins. no harm in having a look.

Agree with you mate,but if its a number of circuits then the Ze would have shown something pointing towards a common earth problem, it could be handy if knipex shared his readings with us, in fairness there is a big differance between max Zs for B and C types, and have seen situation in large refrigeration systems where a type D as been specified but unable to be used due to Zs being way to high for them. You raise a good point though and where earthing integrity is concerned should we be looking at 1667 as per all these RCD installed circuits go,or max Zs as per the breaker itself. If the readings would satisfy requirements for say a B type then I suspect all is good , just have to see.