help!!!!

[mikeymoo]

while testing the Zs on a upstairs lighting circuit it keeps tripping the rcbo??? I'm using a megger 1557 with 3 leads. Line, neutral and earth and have it set on no trip. Yet it still trips? All other tests are fine.. Any ideas?? its just the one lighting cct..

 

[Mr Mark Sparks]

is it a 6a if so make sure all lts on that circ are off
lets say its 6a and with lts on its already pulling 5a then the aditional current induced by the tester could cause circ to overload

 

[Spudnik]

Swap out the RCBO for an MCB for the test.

 

[mikeymoo]

Yeah its a 6. Also tried it without load. The total load was only 1.8amp anyway. Tried with another RCBO. Does the same. Insulation resistance >299. 0.55 R1+R2. Trips at 26mA, 18.1ms.

 

[Mr Mark Sparks]

in that case as j said use mcb for test or calc zs from ze r1 r2 and put a note to say why

 

[Spudnik]

Meggers use 25mA for the no trip loop test.

 

[MikeK]

Meggers use 25mA for the no trip loop test.

Hi Jason

Sorry they dont.

Meggers use 25ma for current L to earth, but ramp to 10A for L/N. (Even on 3 lead non trip test)

Megger themselves do not guarentee they will not trip 6A MCBs.

I beleive Megger do offer software upgrade for this.

MikeK.

 

[Spudnik]

Hi Jason

Sorry they dont.

Meggers use 25ma for current L to earth, but ramp to 10A for L/N. (Even on 3 lead non trip test)

Megger themselves do not guarentee they will not trip 6A MCBs.

I beleive Megger do offer software upgrade for this.

MikeK.

Interesting you say that as i had Megger separates a while ago and im sure it said it tested at 25mA .

Oh well, i stand corrected!

 

[old dog]

hi a loop test will sometimes trip a 6amp MCB as it delivers a high current for a short period of time.
this actually comes up as a 2391 question.
part b of the question how do you overcome this.
by calculation

 

[mikeymoo]

hi a loop test will sometimes trip a 6amp MCB as it delivers a high current for a short period of time.
this actually comes up as a 2391 question.
part b of the question how do you overcome this.
by calculation

Cheers for that old dog.. That explains the matter.