~Here is an odd one

[electrizion]

Doing some repairs at a school after a P.I.R.

One of the problems the report bought to light was the failure of a 61009 rcbo to trip when the test button is pressed.

The rcbo feeds some socket outlets in a classroom into which are plugged four pc`s and 4 crt monitors. To cut a long story short unplug any two of the monitors or pc`s the rcd operates correctly plug them in again and it fails to operate when the button is pressed it chatters but will not trip.

The wiring is old 7.029 no cpc conduit system ( as is most of the school)

The ELI is within spec the rcd operates within spec under test.

I have replaced the rcbo with no effect, connected the ring to a different rcbo and phase still no effect.

Any ideas please

 

[Andy™]

what type are the RCD's? the computers may have a DC effect stopping it from tripping (similar to how some test kits saturates it with DC when doing EFLI)

What are the trip results with a test kit?

 

[electrizion]

what type are the RCD's? the computers may have a DC effect stopping it from tripping (similar to how some test kits saturates it with DC when doing EFLI)What are the trip results with a test kit?

Have not got the results with me there at the school will post them later.

The rcbo is a MEM C 32

 

[SPECIAL LOCATION]

Are the computers switched on when doing test?

or just plugged in BUT swirtched off?

If PC's are on... have you got much Earth leakage from the IT equipment?

 

[electrizion]

They are plugged in but switched off, i have not checked them for earth leakage yet.cheers

 

[binky]

Try contacting the RCD manufacturer's technical helpline - they might be able to shed some light on this. Failing that try a different make (ie a decent one) and see if that makes a difference

 

[kme]

Try contacting the RCD manufacturer's technical helpline - they might be able to shed some light on this. Failing that try a different make (ie a decent one) and see if that makes a difference

:^O :^O:^OApplaud SmileyApplaud SmileyGuiness DrinkGuiness Drink

 

[electrizion]

Try contacting the RCD manufacturer's technical helpline - they might be able to shed some light on this. Failing that try a different make (ie a decent one) and see if that makes a difference

MEM not decent then?

Problem still exists but manufacturer is looking into it oddly enough they have never had this type of fault reported and it is not in their database.

 

[SLIPSHOD & SLAPDASH]

Forget that. Andy is correct in as much as lots of electronic equipment has power supplies that 'put out' a DC current as leakage which will stop an RCD operating. The RCD should be tested with no outgoing cables connected. Try that and tell us whats happens.

 

[Nicky Tesla]

Forget that. Andy is correct in as much as lots of electronic equipment has power supplies that 'put out' a DC current as leakage which will stop an RCD operating. The RCD should be tested with no outgoing cables connected. Try that and tell us whats happens.

it was said earlier that they were plugged in but switched OFF

 

[electrizion]

Rcd with phase and neutral disconnected works fine

RCD phase and neutral connected nothing plugged into sockets works fine

RCD with 2 pc`s 2 crt monitors plugged in but not switched on works fine

RCD with 3 pc`s 3 crt monitors plugged in not switched on slight hesitation when test button is presses.

RCD with 4 pc`s 4 crt monitors plugged in but switched off test fails

I imagine that these monitors and pc`s are in their standby mode rather than completly switched off.

Incidently if i disconnect the neutrals leaving the phase connected to the rcd and the four pc`s and four monitors plugged in the rcd still fails to trip when pressing the test button.

 

[batty]

If you read most books about testing RCD's they say load should be disconnected during tests. So I would think you need to unplug whats on the circuit.

Batty

 

[Andy™]

it was said earlier that they were plugged in but switched OFF

switched off in what way

socket switched off, of computer 'switched off' but still on drawing power

 

[electrizion]

switched off in what waysocket switched off, of computer 'switched off' but still on drawing power

both monitors and pc`s switched off but power still applied to their iec sockets