RCD not tripping on x1In but does on x5n

[crisbie]

Hi - hope someone can help.

Installed a new Wylex CCU. Dual RCDs.

When I test the RCDs with the test button - no problem, they both trip.

Testing via my meter at x1In they dont trip.

Testing via my meter at x5In they trip on 0/180 within 18-25ms - so fine.

Insulation resistance tests on circuits >200Mohm except for a couple which are around 6Mohm. (Quite old 20+yrs installation).

r1+r2 all way within tolerances.

CPC continuity all checked out well.

Ze 0.14ohm

Earthing system TNS.

I am using a Dilog 9083P meter which has the plug which can be used for testing RCDs at the nearest convenient socket. But I get the same results if I take cover off CCU and test a circuit directly.

There is a SWA supply down to garden shed with RCD protected sub board - not sure if this is relevant or if discrimination is affecting this in some way.

Both RCDs behave in exactly the same way.

Any advice on what I am missing/or can break this down to diagnose better.

many thanks in advance.

 

[sparkytim]

Try disconnecting ALL circuits from RCDs and test straight of RCD terminals.

 

[crisbie]

Will do. thanks for coming back so quick.

 

[ianmacd]

When was your meter last calibrated and when did you last change the batts?

 

[SPECIAL LOCATION]

Try disconnecting ALL circuits from RCDs and test straight of RCD terminals.

:Salute :x :Applaud:Applaud

Hi - hope someone can help.Installed a new Wylex CCU. Dual RCDs.

When I test the RCDs with the test button - no problem, they both trip.

Testing via my meter at x1In they dont trip.

Testing via my meter at x5In they trip on 0/180 within 18-25ms - so fine.

Insulation resistance tests on circuits >200Mohm except for a couple which are around 6Mohm. (Quite old 20+yrs installation).

r1+r2 all way within tolerances.

CPC continuity all checked out well.

Ze 0.14ohm

Earthing system TNS.

I am using a Dilog 9083P meter which has the plug which can be used for testing RCDs at the nearest convenient socket. But I get the same results if I take cover off CCU and test a circuit directly.

There is a SWA supply down to garden shed with RCD protected sub board - not sure if this is relevant or if discrimination is affecting this in some way.

Both RCDs behave in exactly the same way.

Any advice on what I am missing/or can break this down to diagnose better.

many thanks in advance.

Will do. thanks for coming back so quick.

TBH a lot of what you have written above is irrelevant to the problem..

Are you a qualified spark or DIY or still training?

Do you have a copy of the On-Site-Guide?

If so why is it that so few electricians actual read the 'guidance' in the "ON-SITE-GUIDE"?

Chapter 11 would be your first port of call for any RCD questions..

read paragraph 11.1 General Test Procedure out load to yourself..

something along the line of....

Tests on load side of RCD near to its point of installation WITH loads disconnected.

So as Sparkytim points out..test them in the board with nothing else connected.

as per the recommended IEE BS7671 Guidance!!!

:C

 

[crisbie]

Thanks. Will try the ramp test meter has that facility.

Meter was calibrated at Xmas just gone.

SparkyTim, so you know, yes have followed Guidance Note 3 and tested, single circuit with load disconnected from RCD load side to appropriate CPC. Same problem.

 

[SPECIAL LOCATION]

single circuit with load disconnected from RCD load side to appropriate CPC. Same problem.

??

If an RCD fails with power but no other items connected then its most probably a manufactures warranty replacement job no?

Consider one of those plug in RCD adaptors...

If you plug your tester in

You just have power on one side direct onto your tester..

Nothing else in the equation?

except the RCD

Have you got your earth probe connected to earth.. as in the main earth bar?

Any dodgy parallel paths around N-E causing errors..

Test the RCD out of the board with a fly lead to a plug.

:|

 

[ianmacd]

I could accept one failed RCD but not 2 as that would suggest a whole batch issue and that would have been picked up by now by other installers too. Logically, issue is a local problem causing them not to trip. Can you ramp test as previously suggested? What about your batts, tried fresh ones? Tested the tester on a known rcd (e.g. one in your house)?

 

[mikep]

I always test them on their own straight on the busbar neutral and earth, sounds like a dodgy RCD.

 

[batty]

Perhaps its the weather my Fluke is playing up refusing to trip memshield 3 RCBO's on the four DB boards I have just fitted. Have tried them at the boards and at sockets makes no difference. So I have tried them with my old Robin tester and they are tripping out fine, out of the four I fitted only one would trip as it should with the Fluke not sure what to make of it.

 

[ianmacd]

As has been said before, its a fluke if it works

 

[steptoe]

PICNIC

DHTNT

 

[crisbie]

Changed batteries - no change. Batteries were pretty fresh anyway.

Did ramp test and first RCD tripped at 34mA.

Repeated tests and now getting compliant results on both RCDs at CCU. (have abandoned testing via nearest socket)

Repeated tests several times on both RCDs with consistent results.

All seems fine.

---------- Post Auto-Merged at 19:58 ---------- Previous post was made at 19:58 ----------

Thanks everyone for help and ideas.

 

[steptoe]

Changed batteries - no change. Batteries were pretty fresh anyway.Did ramp test and first RCD tripped at 34mA.

Repeated tests and now getting compliant results on both RCDs at CCU. (have abandoned testing via nearest socket)

Repeated tests several times on both RCDs with consistent results.

All seems fine.

---------- Post Auto-Merged at 19:58 ---------- Previous post was made at 19:58 ----------

Thanks everyone for help and ideas.

good, cos you are meant to be testing the RCD, not the circuit.

why oh why oh why do people not read testing procedures.?

not just you crisbie, this comes up all the time.

 

[NozSpark]

So how do we go about testing a RCD while being assessed and using safe isolation techniques,,, because you aren't meant to have the cover removed with the power on, but manufacturers say that you should test the RCD as close to the source as possible (that would be the bus bar)???.

 

[steptoe]

I have never had any issue with assessors testing the RCD at the CU, or even for that matter having the cover off live in certain instances,

I think sometimes they like to see just what method of approach you use with a live busbar/CU.

last year he had me test one RCD at the lights, and the other one at CU, then asked me what I preferred and why.

 

[ianmacd]

Think I may have refused testing at the lights, steps, on h&s grounds. also, as you said, it's not then in isolation either.

 

[steptoe]

I think that may have been why he got me to do both, then explain to him where I test and why, TBH, I get on really well with him and have no issues with how he does things, usually do more chatting than work. I think they can tell by a quick chat and how you simply go about the approach to the procedure as to your ability rather than the text book approach and have you test everything in sight.

 

[Andy™]

good, cos you are meant to be testing the RCD, not the circuit.why oh why oh why do people not read testing procedures.?

not just you crisbie, this comes up all the time.

i always test at a socket. its a well knwon fact that some loads etc can effect the operation of the RCD. if you knowingly 'remove' said problem to get the RCD to pass test, then your probably one of those who adds some liquid to an earth rod to get an acceptable reading. it looks fine, but as soon as your gone, you may have left it dangerous.

 

[Lee321]

but andy the installation doesn't include items plugged into it! ??

if its correct as an installation then you plug something in and nuisance tripping starts its an outside of what is tested