RCD not tripping on test

[jmc1683]

I am doing complete installation test on domestic house, working off two dual RCD distribution boards. There are socket rings as well as other circuits connected on DB1 and everything seems to be testing ok.

on DB2 I have the following circuits on one RCD,
Utility Ring, Downstairs sockets, Kitchen appliance, Lights kitchen, lights stairs.

the ring sockets are not tripping the RCD. Here are their details,

Utility Ring
L-L 0.26
N-N 0.26
E-E 0.41
R1 + R2 0.27
Ins Res +999 +999

Downstairs sockets
L-L 0.26
L-L 0.26
E-E 0.48
R1 + R2 0.25
Ins Res +999 +999

Kitchen App
L-L 0.19
N-N 0.19
E-E 0.28
R1 + R2 0.16
Ins Res +999 +999

 

[telectrix]

test RCD with all it's circuits disconnected.

 

[jmc1683]

sorry, forgot to mention I did that, also changed swapped RCD's from DB1 for peace of mind. RCD is fine.

 

[Plonker 3]

Did you disconnect all circuits or just switch the MCBs off?

 

[jmc1683]

I removed the bus bar and neutral

 

[SPARTYKUS]

What are the test results for "lights kitchen", "lights stairs"................

 

[jmc1683]

ooops, just realised i listed the wrong circuits!
sorry, been a long day.

here are all 5 circuits on affected RCD

Heating
R1 + R2 0.16
Ins Res +999 +999

Immersion
R1 + R2 0.28
Ins Res +999 +999

1st floor sockets
L-L 0.79
N-N 0.79
E-E 0.52
R1 + R2 0.55
Ins Res +999 +999

2nd Floor sockets
L-L 0.75
N-N 0.76
E-E 1.20
R1 + R2 0.54
Ins Res +999 +999

Study socket ring
L-L 0.36
N-N 0.36
E-E 0.55
R1 + R2 0.28
Ins Res +999 +999

 

[Octopus]

What make of RCD is it?

 

[jmc1683]

Wylex, 80A 30ma

 

[Plonker 3]

Did you swap both RCDs over? Or just the one that wouldn't trip onto the other side?

Have you tried testing with all the circuits connected?

 

[jmc1683]

I swapped the RCD that was not tripping with the one from DB1

 

[Plonker 3]

Did it test fine with the new RCD?

 

[jmc1683]

I swapped the RCD that was not tripping with the one from DB1 that I knew was, I then retested socket circuits form DB1 and they tripped the RCD fine

then the RCD from DB1 wont trip on DB2 same like the original, hope that makes sense

 

[Octopus]

Will the RCD set and trip using the test button?

 

[SPARTYKUS]

How are DB1 & DB2 configured, as in is DB2 fed by an MCB from DB1?

 

[jmc1683]

Yeah, should have mentioned that earlier. sorry

 

[Plonker 3]

Sounds like a duff RCD to me then, unless I am reading it wrong.

 

[jmc1683]

No, DB1 and DB2 are fed from henley block, fed from meter

 

[SPARTYKUS]

Have you got the figures for each RCD - x1/2 times, etc and ramp

 

[jmc1683]

well the results from original RCD on DB1,

utility ring
times 1 - 27.2 ms
times 5 - 8.18 ms

downstairs sockets
times 1 - 27.4 ms
times 5 - 7.98

I didnt record the results after i swapped RCD, just that it did trip on test

 

[GLENNSPARK]

why is there .79 on the live conductor end to ends and .52 end to end on the CPC on the first floor sockets?

- - - Updated - - -

and whats the Zdb?

 

[Octopus]

Whats the Ze at the "duff" Db - sounds like you haven't got an earth.

 

[Plonker 3]

I would like to think the OP has done a R1+R2 before energizing the DB,or is that asking for too much?

 

[GLENNSPARK]

I would like to think the OP has done a R1+R2 before energizing the DB,or is that asking for too much?

well...it appears he`s done it on the finals....
but the sub?

hence my post at #21

 

[jmc1683]

I was looking at that aswell, didnt investigate, you think that has something to do with it? RCD should still trip on test right?

 

[Plonker 3]

It should yes, try answering the other questions too please.

 

[LED Lighting]

I had this lastnight - went to a house - RCD tripping on split 2.
Tested split 1 and no trip upto 550mA

Hit the test button and then ramped it again - tripping at 10mA now - RCD replaced

 

[jmc1683]

got Ze reading of 0.19, thats the extent of the testing i've done this far

 

[Octopus]

I was looking at that aswell, didnt investigate, you think that has something to do with it? RCD should still trip on test right?

What is the Ze?

 

[adslev]

I had this lastnight - went to a house - RCD tripping on split 2.
Tested split 1 and no trip upto 550mA

Hit the test button and then ramped it again - tripping at 10mA now - RCD replaced

Tripping at 10mA??
You sir have replaced a faulty RCD with another faulty RCD
Anyway to the op have you ramp tested the faulty RCD yet?

 

[GLENNSPARK]

I was looking at that aswell, didnt investigate, you think that has something to do with it? RCD should still trip on test right?

eh?.....

 

[LED Lighting]

No faulty unit tripped at 10mA after hitting Test Button - new unit tripping at 28mA

By the way this RCD was less than 6 months old!!!
I installed it last September - Ze 0.18 on a TN-S

 

[jmc1683]

no, will do that. RCD seems fine though. I'm gonna look into that earth reading from 1st floor sockets though, didnt get chance to yet

 

[GLENNSPARK]

no, will do that. RCD seems fine though. I'm gonna look into that earth reading from 1st floor sockets though, didnt get chance to yet

and what makes you think its the CPCs?

 

[GLENNSPARK]

so..once youv sorted out your end to ends....you can just jolly well go round the points again on that circuit for a real value of (R1 R2)....cant you...

- - - Updated - - -

this is sounding more and more like the same old farce....

 

[jmc1683]

well i noticed the readings from 1st floor sockets were strange, and someone else pointed it out here just few mins ago....

L-L 0.79
N-N 0.79
E-E 0.52

 

[Octopus]

no, will do that. RCD seems fine though. I'm gonna look into that earth reading from 1st floor sockets though, didnt get chance to yet

What is the Ze? Surely you got this reading first!

 

[LED Lighting]

well i noticed the readings from 1st floor sockets were strange, and someone else pointed it out here just few mins ago....

L-L 0.79
N-N 0.79
E-E 0.52

Those readings are R1, R2, Rn readings and they look fine to me!

R2 is 66% of R1/Rn

 

[GLENNSPARK]

Those readings are R1, R2, Rn readings and they look fine to me!

R2 is 66% of R1/Rn

eh?....try 1.67 for a 2.5/1.5...

 

[jmc1683]

0.19, already answered that

 

[spark 68]

Those readings are R1, R2, Rn readings and they look fine to me!

R2 is 66% of R1/Rn

It is r1, r2 and rn for a start on the end to ends, and his r2 is lower than is r1 and rn, it should be 66% higher for 2.5/1.5 T&E

 

[LED Lighting]

It is r1, r2 and rn for a start on the end to ends, and his r2 is lower than is r1 and rn, it should be 66% higher for 2.5/1.5 T&E

Sorry just seen my mistake - sorry!

 

[spark 68]

Deleted: blonde moment Lol

 

[Octopus]

0.19, already answered that

I'm guessing you mean that the Ze is 0.19. Can you set the RCD and does the test button work? I would now venture to suggest that the CPC has a voltage on it.

 

[jmc1683]

sorry mate, you must have joined us late. i already answered everything your asking in the first posts. RCD is setting, test button working, all circuits working fine. checked all connections, swapped RCD....

 

[Octopus]

sorry mate, you must have joined us late. i already answered everything your asking in the first posts. RCD is setting, test button working, all circuits working fine. checked all connections, swapped RCD....

Voltage on the CPC?

 

[dagrat]

It is r1, r2 and rn for a start on the end to ends, and his r2 is lower than is r1 and rn, it should be 66% higher for 2.5/1.5 T&E

Not necessarily, I would agree on an initial verification it should be 1.67 higher, but from what the op says this is an existing installation and the low r2 is probably due to parallel earth paths so not really a problem

 

[Risteard]

well the results from original RCD on DB1,

utility ring
times 1 - 27.2 ms
times 5 - 8.18 ms

downstairs sockets
times 1 - 27.4 ms
times 5 - 7.98

I didnt record the results after i swapped RCD, just that it did trip on test

One RCCB can't have two different trip times.

 

[spark 68]

Not necessarily, I would agree on an initial verification it should be 1.67 higher, but from what the op says this is an existing installation and the low r2 is probably due to parallel earth paths so not really a problem

Agreed, but as this is domestic and subject to being tested properly (end to ends) ie. disconnected at the CU/DB end, you would need at least two parallel paths to lower the reading, it should warrant further investigation to rule this in or out when you do not get the expected readings, especially while fault finding.