RCD,Rcbo tripping on earth loop impedance test

[tuckermot]

Hi every one
I have a robin 1620 multifunction meter and i am commencing my 2391 in march.My meter does not have a D,lock so when doing earth fault loop testing on circuits protected with rcds and rcbos the test current some time trips the breaker before the meter can get a reading has any one had this problem and what can i do to get round this problem the meter is new back from calibration can a D,lock be fitted to my meter help!!
thanks

Rich

 

[Guest123]

Hey.

The way I used to get around it before I got a new meter, was to replace the RCD with a main switch during the test and also to replace the RCBO with a standard MCB, again only during the test. Obviously this is done on site and I dont know how your course provider would view this method.

Other than that it's a new meter with D-lok I'm afraid.

Cheers

 

[tuckermot]

Hi leenytheloon
Thanks for response are you saying before d,loks were put in meters you had to do this all the time ,can the rcd/rcbo be bypassed anyway or linked out other wise durring my practical i am going to run out of time
thanks
Rich

 

[WarrenG]

If your meter doesn't have D-lok then I think you can use the measured values of Ze and R1+R2 and apply the 80% rule.

Most modern testers have the D-lok now in place.

 

[mrloy99]

Hi every one
I have a robin 1620 multifunction meter and i am commencing my 2391 in march.My meter does not have a D,lock so when doing earth fault loop testing on circuits protected with rcds and rcbos the test current some time trips the breaker before the meter can get a reading has any one had this problem and what can i do to get round this problem the meter is new back from calibration can a D,lock be fitted to my meter help!!
thanks

Rich

will your college not supply you with one for your practical test?
mine did.

 

[tuckermot]

Hi do you mean zs= ze + (R1+R2) of final circuit being tested multiply it by 0.8 for ambient temps then compare with max readings in regs for the breaker/mcb is this acceptable to put down on test sheet ??

 

[WarrenG]

Yes - it states in GN3


Earth fault loop impedance Zs may be determined by:

1) direct measurement using an earth loop impedance measurement instrument, or​

2) measurement of R1 + R2 during continuity testing and adding to Ze, i.e.​

Zs = Ze + (R1 + R2)​

Mines an old copy - P53?​

 

[Guest123]

If your meter doesn't have D-lok then I think you can use the measured values of Ze and R1+R2 and apply the 80% rule.

You're right, but the only thing I would say is that as he is doing his 2391 course in the practical exam they'll probably want to see him carry the proper test to show he knows how to do it.

Just a thought

 

[WarrenG]

lol............yes agreed....forgot about that bit

Looks like you may need to borrow a meter!

 

[super spark]

Hi do you mean zs= ze + (R1+R2) of final circuit being tested multiply it by 0.8 for ambient temps then compare with max readings in regs for the breaker/mcb is this acceptable to put down on test sheet ??

Ambient temperature factors are found in table 4B1, the factor of 0.8 is the rule of thumb and is applied to the max Zs values on tables 41. to account for operating temperatures under fault conditions and to err on the side of safety.

Zs values can only be taken on an energized circuit, as such in many situations this could be un-safe (i.e, shower- whilst stood outside the bath reaching over) and it is not a requirement of gs38 to have a D-lock. In this case I would describe how I would take a Zs test with a meter incorporating a D-lock or similar device and then carry out the r1/r2 test & Ze test respectively and show them the calculation, they will be much more impressed.

 

[tuckermot]

Thank you super spark yes i do understand that the zs reading can be measured or done by calculation and as i have allready got ze and R1 + R2 of the circuit being testedted i beleive both examples are acceptable and can be recorded on the test sheet
cheers

 

[hughesy]

I short out the live and neutralof the rcd then test dont think this is an approved method though

 

[gerry jones]

Hi..

Suggest you start spending and get a new tester with D lock.. less bother.

 

[brucegenerator]

There is no time for messing about just get a decent meter.

 

[gerry jones]

Hi... Don't mess about .. spend some money and get yourself a `D` lock test meter.. Megger 1552, or similar.