Testing of exposed RCD.

[eveares]

Just a RCD operating with the front cover removed, 20w load connected between line out and neutral in. Shot at 50 FPS using my Panasonic HDC-SD600.

Also before the video, I wired a Plug to the Input of the RCD and a 20w CFL lamp to the output of the RCD, I then wired a switch in between the line in and the line out; surprisingly the RCD did not trip when I turned the switch on and the bulb stayed illuminated!?

Either the switch had a high impedance relative to through the RCD letting very little current bypass the RCD, or something else is going on which I don't understand.

 

[PrenticeBoyofDerry]

I don't understand the demo, I could visual see the trip switch moving between on/off. But could not see when it was on/off load. Nor could I see any path to earth.

 

[eveares]

But could not see when it was on/off load

Before it tripped it was on, after it tripped it was off; repeated from 4 different angles.

Nor could I see any path to earth.

20w load connected between line out and neutral in. Effectively recreating what the test button does.

 

[PrenticeBoyofDerry]

Correct me if I am incorrect, but if you by-pass the coil with both line and neutral does this not defeat the object of the test? or have you managed to recreate in some way the imbalance on the coil?

 

[Lectrician]

He bypassed one, not both.

 

[AndyPRK]

The problem is that the light is staying on then ?

Maybe the pole of the RCD you are using is staying closed? The obvious answer. Can you check continuity.

 

[Spark123]

Also before the video, I wired a Plug to the Input of the RCD and a 20w CFL lamp to the output of the RCD, I then wired a switch in between the line in and the line out; surprisingly the RCD did not trip when I turned the switch on and the bulb stayed illuminated!?

Either the switch had a high impedance relative to through the RCD letting very little current bypass the RCD, or something else is going on which I don't understand.

With the setup described there'll be two paths (via the switch and via the coil) so resistance of each path comes into play as to how much current goes each way and also there'll be no inrush current.

 

[AndyPRK]

So you are saying once the lamp has struck there is enough current thru the coil to keep it on.

U could try a proper lamp

 

[JohnW2]

Or it could be to do with 20w only being around 8.3mA ...

Surely 83 mA, not 8.3 mA - i.e. plenty enough to trip a 30 mA RCD.

Kind Regards, John

 

[PrenticeBoyofDerry]

He bypassed one, not both.

Well if that be true, you would expect it trip!

 

[333rocky333]

Be carefull, I once had a problem testing earth loop as it kept tripping an rcbo in an enclosure, as it was single pole I thought id just link live in to live out rather than force the cables out as it was tight, not sure what happened next or why , but i turned the supply mcb back on, and the rcbo started smoking,

 

[kai]

A safe way to functionally test an RCD, before connection to any supply, is to use a 200mA Continuity tester. Set the RCD to the ON position first. Place one probe of the Continuity tester onto the Phase input of the RCD, and the other probe onto the Phase output of the RCD. Press the Measure button on the Continuity tester. The RCD should trip at once, as 200mA is effectively passing through only one side of the device. Reset the RCD, and repeat the excercise with the Neutral Input and Outputs instead. It should trip at once.
Give it a try yourself - note that it only works on electro-mechanical RCD's and NOT RCBO's which tend to be electronic in nature, and needs mains power to operate.

 

[JohnW2]

A safe way to functionally test an RCD, before connection to any supply, is to use a 200mA Continuity tester. ..... note that it only works on electro-mechanical RCD's and NOT RCBO's which tend to be electronic in nature, and needs mains power to operate.

One problem there is that I personally have not come across a non-electronic consumer RCD for many years, although I gather that some are still being made/sold. However, if you do have one, another safe way to test is simply to use a low voltage AC source - an electro-mechanical RCD knows nothing about voltage, only current, so it can be tested at, say, 12V just as well as at 230V.

Kind Regards, John

 

[kai]

I did my test on various Wylex RCD's recently. (New 17th edition type).

 

[JohnW2]

I did my test on various Wylex RCD's recently. (New 17th edition type).

What is a "17th edition RCD"?

Do you believe they were electromechanical, rather than electronic?

Kind Regards, John