Mem Alb321 Rcbo Not Tripping

[marky1]

Hi Guys

installed new circuit for shower (7.8kW 230v/8.5kW 240v) in 6mm today. I also installed a mem alb321 rcbo. Test results were r1+r2 0.07, I/R 500+ Zs 39.68. RCBO test button works but fails to trip during test. I removed the load & tried RCD test again but no trip. 

Installation is a TT system with 100a 100mA RCD main switch (Ze 36 ohms). 6mm main earthing conductor, 10mm bonds to gas & water.

During RCD tests the 100mA tripped at 17.6ms at x5.

Out of curiosity i then tested the rcbo for the hob & socket circuits. Both failed to trip during test, yet the 100mA tripped during x5.

I even turned off all circuits except circuit being tested & same results, none of the 3 rcbo's will trip whether tested at the rcbo or at hob/shower or sockets.

Any help appreciated

Thanks

 

[steptoe]

where did you test at?

some RCBOs will NOT test at ther terminals, something to do with where the current is measured is after the terminal,

use a couple of short jumper wires and test outside the body of the RCBO

the other thing,

is the earth fly-lead connected?

 

[kerching]

where did you test at?

some RCBOs will NOT test at ther terminals, something to do with where the current is measured is after the terminal,

use a couple of short jumper wires and test outside the body of the RCBOthe other thing,

is the earth fly-lead connected?

Well,done that man!

Buy him some bread and butter.

I read somewhere that the MEM ones can be a bit moody if you test at the terminals

Just remembering

 

[marky1]

I tested both at the rcbo & shower (also hob isolator & socket outlets ref other existing two rcbo's)

Yes the earth fly leads are connected

 

[steptoe]

is your polarity correct?

 

[marky1]

yes, even double checked before i left, 

 

[steptoe]

• where did you check at?

you may have reverse polarity running through the rcbo and it 'seems' ok cos its been connected backwards, so to speak
 

 

[NozSpark]

I've had this happen where another circuit has a N-E fault

 

[marky1]

i tested at the terminal screws on the rcbo, also on the terminals of the shower.

I will try the jumper wire idea & see what happens.

  :signthankspin:

 

[Evans Electric]

He,s tested at shower terminals  , which is where it counts and it doesn't trip .    I'd get the MEM Tech. Rep in ...sharpish , they can't be that old .  Worrying  eh!      Not another re-call is it ?

When this happens I often jam my old Drummond mains tester across L- E   if  that  doesn't trip  it , it has to beggered. 

The "Proper"  RCD  ( 100mA   DP  main switch )  is tripping .  HHmmmm  .

I was looking at the new MEM range of accessories coming into Denmans and noticed that they are ( of course)  made in China ,

Just noticing . Not commenting  :C

 

[Rob_the_rich]

might be the rcd tester?

I mean the machine, not the person. Worth checking on another installation.

Also, it is not clear to me whether the other two rcbos are the same make and model.

Hopefully marky1 will update us.

 

[Evans Electric]

Ah  yes  good point .... could be the tester ( as in tester ,,not the tester as in the person :innocent ) 

Could try it out on the 100mA   ....is it calibrated ?  Can you trip them with  test lamp?

 

[Steve3948]

What is the make of the tester.

My Megger 1730 will not perform test if parameters are not met.