RCD Fault - can't figure it out!

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davetheglitz

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Just tested an RCD that passes x0.5 (no trip), x1 (23.5ms) 0 degrees x5 (4.4ms) but fails 180 degrees x 5 (Touch voltage >50v - error 4).

Zs at the socket where I measured is 0.39ohms.

Meter is Fluke 1651 - but using the plug and not the dreaded croc clips! Passes the other RCD in the 17th edition board.

Any ideas? Can't think how an RCD could be so selective on what it fails!

Will replace RCD soon!

 

steptoe

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Just tested an RCD that passes x0.5 (no trip), x1 (23.5ms) 0 degrees x5 (4.4ms) but fails 180 degrees x 5 (Touch voltage >50v - error 4). Zs at the socket where I measured is 0.39ohms.

Meter is Fluke 1651 - but using the plug and not the dreaded croc clips! Passes the other RCD in the 17th edition board.

Any ideas? Can't think how an RCD could be so selective on what it fails!

Will replace RCD soon!
have you tried testing at the RCD? direct at the CU?

although I dont think would make any difference in this case, sounds like the coil is burnt on bottom side of the wave..... no idea why it would be like this tho.

 

davetheglitz

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Hi Steps,

Just to say I went back and re-tested yesterday and everything was working. Can only think that I'd exercised the RCD a few times so it wasn't so 'sticky'. I reckon I'm going to have to get a new set of leads for the Fluke to eliminate any other sources of error!

Cheers

Dave

 

davetheglitz

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Hi Binky - are you psychic or what!

Denmans Basic range!

Previously I've been so impressed with their RCD's in that in a dual board each RCD would trip within a couple of milliseconds of each other. Good quality control I thought - but your post has made me ask a few questions!

Were these the boys that caused your Zs hassle at Salcombe?

Cheers

Dave

 

davetheglitz

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Dave..........Change the RCD. Steptoe correctly idents a duff "half-cycle" on the amp section of the RCD.

May test ok now that you`ve "lubricated" it, but it has an inherent fault.

Change it mate.
Hi KME

I can't see why this would be if the device was tripping correctly at x1 on both half cycles.

I'm not familiar with RCD construction, but I would presume that the amp is fed by a diode - which would be proved operational by the x1.

Too low a gain - x1 wouldn't trip.

Too high a gain - would trip at 0.5x.

Am I missing something?

 

steptoe

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but you need to remember that a fluke 1651 will only pass or fail the RCD, after a certain time span it auto fails it.

and at 5x it needs to trip much much faster to pass.

I use a 1652 which fortunately has a ramp facility on it to show at what current the actual trip occurs.

 

davetheglitz

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but you need to remember that a fluke 1651 will only pass or fail the RCD, after a certain time span it auto fails it.and at 5x it needs to trip much much faster to pass.

I use a 1652 which fortunately has a ramp facility on it to show at what current the actual trip occurs.
Thanks Steps - but in this case I don't think that would have helped because although it tripped at x1 I had the dreaded >50v message at x5 (though what I neglected to say however was that the RCD did trip - just that I didn't have a reading I could use). Perhaps this is the one and only application for a reverse ramp? :)

 

YogiM

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There seems to be a problem with Flukes lately when speaking to another engineer.

I have the 1653, few weeks a go doing installation testing, on a rewired house. Doing the ramp test,

X1/2 = 2000 ohms

but X1 = >310 ohms

X5 = >51 ohms

Retested the ramp test on another installation same result which i had passed.

I asked Fluke for a repair cost and that was

 
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