Ramp Test

[Diablo]

Hi all,

When carrying out a ramp test on a 30 mA RCD, what would be the acceptable point that the RCD should trip. I would have thought that for a 30 mA RCD it should be at the 30 mA point. I've tried looking for relevant information on acceptable levels but cant find anything. i tested mine at home and it tripped at 21 mA. I think this makes it a little to sensitive.

I look forward to all your wise thoughts !!!!

Steve

 

[electricAl]

21mA is more sensitive than most perhaps, but perfectly permissible.

26-27mA would probably be the most typical value you`ll come across, but strictly speaking, so long as it trips at x1 (30mA) but not at x0.5 (15mA) it`s compliant

 

[Darkwood]

rcd's trip anywhere between 50% and 100% of their rated value it is common and perfectly normal for a 30ma rcd to trip between 15ma and 30ma but on average in their lower 20's, when ramp testing if their is already an existing leak on the circuit this can reduce the reading further as the existing leak will just add to the meter ramp effect giving a false trip value.If their is no existing leakage on the circuit giving a false value then a reading less than 15ma is prone to nuisence tripping and would consider replacing the rcd.

 

[Mr Mark Sparks]

rcd's trip anywhere between 50% and 100% of their rated value it is common and perfectly normal for a 30ma rcd to trip between 15ma and 30ma but on average in their lower 20's, when ramp testing if their is already an existing leak on the circuit this can reduce the reading further as the existing leak will just add to the meter ramp effect giving a false trip value.If their is no existing leakage on the circuit giving a false value then a reading less than 15ma is prone to nuisence tripping and would consider replacing the rcd.

i agree
did a ramp test under load the other week and it went in 15ms and with no load 27ms

 

[Diablo]

Thanks for the information Guys, all very useful. I will bear this in mind in the future.

 

[zupos40]

Hi all,

When carrying out a ramp test on a 30 mA RCD, what would be the acceptable point that the RCD should trip. I would have thought that for a 30 mA RCD it should be at the 30 mA point. I've tried looking for relevant information on acceptable levels but cant find anything. i tested mine at home and it tripped at 21 mA. I think this makes it a little to sensitive.

I look forward to all your wise thoughts !!!!

Steve

No steve 21mA is fine this is within tolerance, I once read an old BBC document which was based on BS standards of the time and ramp test was only required on German installations, but the standard quoted 18mA to 30mA, but I have found ramp testing very useful, when faultfinding nuisance tripping as a result of a large number of electronic equipment installed on 30 mA RCD.

It great to test each item of leakage current, then RCD and explain the because of the large amount of leakage current due to number of item installed, this is why RCD is tripping.

 

[c.boy]

rcd's trip anywhere between 50% and 100% of their rated value it is common and perfectly normal for a 30ma rcd to trip between 15ma and 30ma but on average in their lower 20's, when ramp testing if their is already an existing leak on the circuit this can reduce the reading further as the existing leak will just add to the meter ramp effect giving a false trip value.If their is no existing leakage on the circuit giving a false value then a reading less than 15ma is prone to nuisence tripping and would consider replacing the rcd.

Changed alot of d/bs in the past few months, and all of my fuses are rcbos for every circuit all type Bs.on my tripping times x1 both sides of the wave is norm 27.9 and x5 is always around 8.0 - 8.7. do you think these readings are fine??? always thought x1 is under 200ms and x5 under 40ms tripping times???? i dont do a ramp test tho!!!

 

[Darkwood]

Changed alot of d/bs in the past few months, and all of my fuses are rcbos for every circuit all type Bs.on my tripping times x1 both sides of the wave is norm 27.9 and x5 is always around 8.0 - 8.7. do you think these readings are fine??? always thought x1 is under 200ms and x5 under 40ms tripping times???? i dont do a ramp test tho!!!

The quicker the better i tend to get similar readings but just wondering if you getting confused because i was discussing ramp testing and mA needed to trip said device and you are discussing miliseconds trip time which as you mentioned x1 & x5 need to be within regs.

 

[TPES]

i agree
did a ramp test under load the other week and it went in 15ms and with no load 27ms

Is this how you would be testing for a faulty appliance? is this the method? switch each appliance on under load and take a reading of what the RCD is tripping at, if it is very low on one of the appliances and the rest average out then you have found your faulty appliance?... how low would it need to be.. less than 15ms? how relaible is this method.. is it 99% accurate?

 

[Darkwood]

Is this how you would be testing for a faulty appliance? is this the method? switch each appliance on under load and take a reading of what the RCD is tripping at, if it is very low on one of the appliances and the rest average out then you have found your faulty appliance?... how low would it need to be.. less than 15ms? how relaible is this method.. is it 99% accurate?

Bloody hell this is a blast from the past(the post i mean). You would be better using a clampmeter with mA range to locate an appliance this ramp test is best for checking faulty rcd,rcbo's but needs doing without load which is usually best to disconnect the circuit to ensure no inherent background leak is there, this way the ramp test is correct and not giving false results.

 

[m4tty]

i agree
did a ramp test under load the other week and it went in 15ms and with no load 27ms

If you dont have mA range on clamp meter only amps is it possible to use above method to check for faulty appliance causing rcd to trip

Thanks

 

[ian.settle1]

If you dont have mA range on clamp meter only amps is it possible to use above method to check for faulty appliance causing rcd to trip

Thanks

Depends upon the type of clamp on ammeter you use as there are ones to measure mA and leakage current.

 

[m4tty]

sorry didnt explain myself very well there. Can you do rcd ramp tests under load then not under load to measure leakage current with MFT

Cheers

 

[Darkwood]

sorry didnt explain myself very well there. Can you do rcd ramp tests under load then not under load to measure leakage current with MFT

Cheers

This method isnt always conclusive as earth leakage within the circuit may corrupt your readings even when all appliances are unplugged, although an insulation test prior should give you an idea to the integrity of the wiring then this method could be used if your insulation test is ok, but is crude as you dont see the leakage as a reading but as a calculation and because the leakage may not be stable or steady you can only estimate the tripping point of the device which in some cases could be several miliamps out.
The best way if you need to rely on this test is to take 5 readings add them altogether then devide by 5 to get the average, do this for loaded and then unloaded and you should be as near as dammit.