RCD Ramp test

[schoe]

Hi all could someone explain what a ramp test is and how they are carried out, ive heard the term but not really sure what it is,

Thanks a lot

Chris

 

[GLENNSPARK]

Good feature on MFTs this one...it increases the earth fault current in milliamps by increments of 5 milliamps untill the RCD/RCBO trips....gives you the true tripping current of the device so you can see if its sh&gged or not...

 

[Engineer54]

Good feature on MFTs this one...it increases the earth fault current in milliamps by increments of 5 milliamps untill the RCD/RCBO trips....gives you the true tripping current of the device so you can see if its sh&gged or not...

If an MFT increases earth fault current in 5mA steps, how can it give a true tripping current?? If the MFT is one of the new latest models, it may increase the fault current in 1mA steps which will give a far more accurate final value than the latter 5mA MFT kit!!

 

[Deleted member 19807]

my fluke dose 3mA steps on a 30mA test, most of the time on new mk rcds i get 24mA

 

[Rockingit]

I think mine must do it in 1mA steps because the other week I tested a few and they all had 21-25 values. But yes, a really handy way to test what happens.

 

[Darkwood]

My metrel does in 0.1mA steps and consider this very usefull, as for th O/P i'll explain that its only a usefull function if you know how to use it fully as you can work out normal leakage on circuits.
If you first switch of all mcb's so as to drop all loads then ramp test your rcd you will get a trip-mA readout, this is the normal tripping point of your device, lets say 24mA which is common for a 30mA rated device. Then switch your circuits back on and whatever loads you want and re-take the test if you now get a reading of 15mA you can attain that 9mA is naturally leaking under load conditions.
Very useful when sourcing the cause of nuisence tripping as even though its not breaking the threshold of the rcd trip while your there you can figure out by isolating circuits where the offending leakage is likely coming from.

 

[Rockingit]

Darkwood - there's a clamp meter for sale on another thread!! :juggle2:

 

[Darkwood]

Darkwood - there's a clamp meter for sale on another thread!! :juggle2:

Know where you coming from but they have there draw-backs and are space restrictive not always the solution and alot of clamp meters dont have mA ratings... my way same meter can accurately show trip threshold and source leakage, we all can achieve same results if we start carrying 10 different meters around, i already have 8 meters on top of the MFT including 2 clamp meters but as ive just said a clamp meter comes second best against a ramp test :49:

 

[telectrix]

at least with a clamp meter, the batteries don't run out half way through testing.:82:

 

[Engineer54]

My metrel does in 0.1mA steps and consider this very usefull, as for th O/P i'll explain that its only a usefull function if you know how to use it fully as you can work out normal leakage on circuits.
If you first switch of all mcb's so as to drop all loads then ramp test your rcd you will get a trip-mA readout, this is the normal tripping point of your device, lets say 24mA which is common for a 30mA rated device. Then switch your circuits back on and whatever loads you want and re-take the test if you now get a reading of 15mA you can attain that 9mA is naturally leaking under load conditions.
Very useful when sourcing the cause of nuisence tripping as even though its not breaking the threshold of the rcd trip while your there you can figure out by isolating circuits where the offending leakage is likely coming from.

Think you'll find 0.1mA is your testers resolution, not the ramp stepping rate. If you have the top of the range Metrel (didn't check the rest), then the O to 50mA is 1mA steps/ 50 to 100mA is 5mA steps / 100 to 1000mA is 10mA steps.

But i certainly agree with your other comments above!!

 

[Engineer54]

Know where you coming from but they have there draw-backs and are space restrictive not always the solution and alot of clamp meters dont have mA ratings... my way same meter can accurately show trip threshold and source leakage, we all can achieve same results if we start carrying 10 different meters around, i already have 8 meters on top of the MFT including 2 clamp meters but as ive just said a clamp meter comes second best against a ramp test :49:

Oh no it's not, a leakage clamp meter is by far a better tool for getting to the bottom of a leakage problem on a circuit/installation...

 

[Darkwood]

Oh no it's not, a leakage clamp meter is by far a better tool for getting to the bottom of a leakage problem on a circuit/installation...

Again yes only when you can get them in due to their physical solid size and shape ... but having said this ive seen a recent one, fluke i think with detachable flexible loop like rubber so if you got one of them then will agree.

 

[Rockingit]

Can't remember what make my little one is (and it's raining outside so not going to find out!) but it does everything it should, is small enough to get into most places (can't think when it's not fitted), has all the right settings and resolutions and cost me about £45.

 

[telectrix]

mine's an alphatek, has a 1mA resolution. does for me.

 

[Engineer54]

Again yes only when you can get them in due to their physical solid size and shape ... but having said this ive seen a recent one, fluke i think with detachable flexible loop like rubber so if you got one of them then will agree.

Never had a problem yet!! There is always more than one way to skin a cat so to speak, same thing with using a clamp leakage tester on a circuit.