Ramp test

[tom79bmth]

Just out of interest what reading do you normally get when doing a ramp test on rcd or rcbo 30 ma

Thanks

 

[Paul.M]

24mA - 27mA

 

[Darkwood]

Its load and installation dependent if their is no background leakage then it will normally trip from about 20mA upwards...

Too may variables to give a common answer as the rcd will also vary in its sensitivity give or take 5mA

 

[Paul.M]

Whilst we are on this subject...... Customer last year I added a few extra sockets to her house and all RCD tests were as expected. I put in an outside socket the other month and the RCD test results came back as 31mA FAIL. Tested it a dozen times and results were 31mA every time.

Would you advise a new C/U (old MeM board) just for 1mA over??? I am torn in between Regs and common seance, she is not a rich woman and I dont think it makes a difference.......... Tin hat on for this one Paul

 

[Darkwood]

What are we talking when you got this result... were you ramp testing?

The ramp test is really only for faulting a circuit does the device operate with the required rcd testing and is your meter calibrated?

 

[Paul.M]

What are we talking when you got this result... were you ramp testing?

The ramp test is really only for faulting a circuit does the device operate with the required rcd testing and is your meter calibrated?

x 1 and x 5 are fine. Ramp test gave me 31mA a dozen times? I ramp tested because it was an outside socket for an elderly person that will be using it, plus it is the mother of one of this forum sponsors. He knows a few things about testing (lol) and we came to the conclusion of "it is ok, leave it for now". I will be going back in the next week or so to test it again just for my own piece of mind. A reconditioned RCD is not out of the question but a board change for this house will be expensive, more than what it is worth.

Darkwood you know I fully trust you and your knowledge. Question:- would you leave an RCD at 1mA over the current regs? I know it needs doing but it is going to be an expense all because of 1mA.

Checked this on two MFT's, same results.

 

[Richard Burns]

If you were doing the prescribed testing regime then you would not know that the actual trip current is 31mA, however if the 1x test is OK this should be applying 30mA only and so I would say this is just a slight delay in the tester stopping the ramp, there is probably a +/- 5% error on ramping in the meter specifications or something.

 

[Darkwood]

In the real world taking a few mA across the heart is enough to stop it but we have to have a compromise that avoids unwanted nuisance tripping while still affording a good level of protection now I can see what your saying but I could never condone on an open forum to cut corners or fudge the results as it would be poor advice.:leaving:

Where did you test from, the O/S socket or the rcd itself?

 

[Paul.M]

Mr. DW I tested at the new outside socket first (as you would) to discover the ms readings were higher than 4 months before. Ramp tested the new o/s skt and got 31mA. Knowing the circuit within the house I then ramp tested the new sockets in the bedroom that I installed 4 months prior and received the same results. I then went onto unplugging everything and taking off any load on the up front RCD. Same results.

Personally I think it is time for this RCD to shake hands with St. Peter and walk through the pearly gates.

 

[Darkwood]

Yes as Richard points out and I touched on too your looking to comply with a trip 'time' when your meter give out 0.5, 1, and x5 rated tripping current. The ramp test is for diagnostic purposes and subject to many factors like existing leakage etc... but dropping all the load off would not have decreased this value as any mA leakage on appliances would be an addition to the result on your meter.

Tripping occurs at 24mA on ramp with loads connected
Tripping occurs at 20mA on ramp without loads connected therefore background leakage due to appliances is 4mA

Im confused why your expressing a value that is not part of the test procedure, if you pass the .5/1/x5 test then the meter has created the correct leakage and the trip times are shown.

 

[SirKit Breaker]

If it is for additional protection, and in your case it is, then as long as reg 415.1.1 is met, your RCD is fine.

Cheers.................Howard

 

[nickblake]

I always ramp test mainly for my own records if an RCD then fails i can re ramp and check with the records and combine this with earth leakage tests , Aids fault finding on an RCD

 

[MDJ]

Just out of interest what reading do you normally get when doing a ramp test on rcd or rcbo 30 ma

Thanks

last one I did a few days back was 22

 

[Badged01]

Where do you draw the line? As lots of previous posts have stated, if you're testing to regulations and it passes .... otherwise you could end up opening a whole can of worms for allsorts!

 

[Darkwood]

The issue with ramp testing is the accuracy of the reading, you are often testing against unknowns like load leakage and background leakage on cables... although this would reduce the trip value and not the case for the OP's problem. Ramp testing is a function that should be used in tandom with other diagnosis and not taken at face value on its own merits hence no requirements to use it, you have to remember it is producing a rising 'ramping' current over several seconds - the nature of the electronics and accuracy of the meter have all to be taken into account as well as the time index for voltage to disappear once the rcd has tripped this can be delayed if you have any capacitive effects on the circuit...long enough for the meter just clock up a few mili-amps.

 

[Engineer54]

Give me a leakage clamp meter every time, over a MFT ramp test. Far too many variables regarding the accuracy of a ramp test. It's only been relevantly recently, that MFT's ramped up in 1mA steps, on earlier models, it could be anything between 3 to 5mA steps, not exactly very beneficial when fault finding.

Not sure why anyone would find it remotely necessary to ramp test an RCD device after it had passed all it's standard obligatory tests eg X 0.5, X1, X5, ...seems a pointless exercise to me!!

 

[telectrix]

Yes as Richard points out and I touched on too your looking to comply with a trip 'time' when your meter give out 0.5, 1, and x5 rated tripping current. The ramp test is for diagnostic purposes and subject to many factors like existing leakage etc... but dropping all the load off would not have decreased this value as any mA leakage on appliances would be an addition to the result on your meter.

Tripping occurs at 24mA on ramp with loads connected
Tripping occurs at 20mA on ramp without loads connected therefore background leakage due to appliances is 4mA

Im confused why your expressing a value that is not part of the test procedure, if you pass the .5/1/x5 test then the meter has created the correct leakage and the trip times are shown.

is it not the other way round?

 

[Darkwood]

is it not the other way round?

Must have been tired tel.... I knew the right way round in my head my fingers just typed it wrong