RCD not tripping at 0 Degrees

[gadget300]

Hi,
One of my electricians came across a fault today which we cannot fathom out.
New split load (dual RCD) board fitted, all insulation and continuity and earth loop readings are ok.
When testing the RCD's at 1/2 ,1 and 5 times at 180 degrees the test is as normal, i.e 1/2 no trip, 1 and 5 times it trips within 40ms.
However at 0 degrees the RCD does not trip at all.

This happens on BOTH RCDS, we though we cant be that unlucky with 2 faulty RCDs, but they were changed and it still does the same.

Is this a supply fault - contact the DNO????

ANY ideas????

 

[SirKit Breaker]

Have you tried the test kit on a known good RCD, or have you tried a different tester on the suspect RCD`s. I agree highly unlikely to have 2 duff ones. I can see no reason why the RCd only trips at 180' its only a coil and should trip which ever direction it is energised.
It has to be your tools..pardon the pun.
Cheers....Howard

 

[gadget300]

Have you tried the test kit on a known good RCD, or have you tried a different tester on the suspect RCD`s. I agree highly unlikely to have 2 duff ones. I can see no reason why the RCd only trips at 180' its only a coil and should trip which ever direction it is energised.

Cheers....Howard

Thanks, as its a long distance job - not yet. However the unit was only calibrated in November but I know this doesnt mean much in the real world.

 

[Graeme Harrold]

Have you got the tester set for the right type of RCD? Also try a ramp test if you can do it

 

[ian.settle1]

Have you tried the test kit on a known good RCD, or have you tried a different tester on the suspect RCD`s. I agree highly unlikely to have 2 duff ones. I can see no reason why the RCd only trips at 180' its only a coil and should trip which ever direction it is energised.
It has to be your tools..pardon the pun.
Cheers....Howard

It has been known for parts to be manufactured and found that batches to be defective and later recalled

 

[acvc]

Yeah like the RCDs on the cut-price Wylex c/u's that S***wf*x were doing till recently.

 

[sidekick]

Yeah like the RCDs on the cut-price Wylex c/u's that S***wf*x were doing till recently.

Are you saying that the wylex board has faulty RCDS ???

 

[orac77]

I fitted a wylex cu in march the RCD was defective cost me in time and head scratching and replacement.I just could not believe a new cu was defective.Also fitted a wylex rcbo on a circuit at anorther job,that then had nuisance tripping faults so fitted a new rcbo,same tripping,then wired circuit via rcd protected circuit and has been fine since.Tested two rcds in 10way board last week one had ramp test of 25ma the 2nd rcd was 15ma which seems a bit low to me,and why the big difference

 

[nrg]

I know this is an old post but I have had the same issue today. The property in question has two consumer units. Testing one RCD on Board 1 all tests work as they should @1/2, 1, 5 on both 0 and 180 degrees.

The RCD in board 2 will not trip at 1x on 0 degrees but will at 5x and does for 1x and 5x at 180 degrees.
I have replaces the RCD 3 times all with the same results,3 different makes of RCD. Ramp test comes back with >51

I k now my tester is working fine, and other suggestions ?

 

[sparkenter]

Sound like you may have a neutral to earth fault before the Rcd. Have you carried out insulation tests?

 

[Strima]

I know this is an old post but I have had the same issue today. The property in question has two consumer units. Testing one RCD on Board 1 all tests work as they should @1/2, 1, 5 on both 0 and 180 degrees.

The RCD in board 2 will not trip at 1x on 0 degrees but will at 5x and does for 1x and 5x at 180 degrees.
I have replaces the RCD 3 times all with the same results,3 different makes of RCD. Ramp test comes back with >51

I k now my tester is working fine, and other suggestions ?

Are you testing at the RCD with all loads isolated? Are there any ballast or other such devices on the circuits fed by the RCD?

 

[Marvo]

Sound like you may have a neutral to earth fault before the Rcd.

I don't understand your reasoning. What type of N-E fault are you referring to and why would it cause the RCD to fail the test as outlined by nrg above?

 

[moddeydhoo]

Had a prob like that a while ago, tried my spare meter worked ok, had other meter re cal

 

[dagrat]

Really can't think why it would trip at 180' but not at the other side of the waveform! does smack of test meter fault.

 

[Farmelectrics]

explain ramp test for me please