RCD Verification Device, Advice would be appreciated

[calltronics]

Hi,

Nice to read some familiar names and lots of new ones on here.

I do not know if any of you familiar names remember but I launched my CalCard on this site many years ago and learnt a lot from people like yourselves.

Lockdown and time on my hands has prompted me to do both an online record tool and an RCD verification device.

The latter is currently commercially sensitive hence I am limited to what I can tell you for the immediate future. The issue I am facing is the requirements of the RCD verification device and the pre-sets of the device.

Basically, it is a box. You plug it into a socket and then plug your RCD tester in. Then set the parameters on the device to emulate the operation of an RCD. A test instrument would see it and measure it as an RCD.

The main difference between my solution and a pre-defined socket; is that I have four set levels of trip current and four set trip times. All of which are highly stable and accurate. Achievable in stable electronics not mechanical relays. In addition to these four settings, I have also included four settings for the Ze Loop impedance.

Now my question is simple as I cannot find anywhere a definitive answer or best practice guide. So, I am calling on your experienced input.

What would be your suggested pre-set parameters to verify an RCD instrument?

1. Current Trips.
   
   
   6mA
   
2. 30mA
   
3. 100mA
   
4. 300mA
   

[*]Trip Times

1. 
   
   5mS
   
2. 40mS
   
3. 200mS
   
4. 400Ms
   

[*]Ze

1. 
   
   0.5Ω
   
2. 1 Ω
   
3. 5 Ω
   
4. 25 Ω
   

 

[Murdoch]

Who do you think would buy such a device?

For what purpose?

If successful, it would also need calibrating, so doubling my overhead per year.

Or maybe I am misunderstanding

 

[calltronics]

Who do you think would buy such a device?

For what purpose?

If successful, it would also need calibrating, so doubling my overhead per year.

Or maybe I am misunderstanding

I think you might be misunderstanding.
it is a device for "ongoing verification calibration" of your RCD tester in line with the requirements for use of instrument for test and inspection.

No calibration is necessary as its a verification device that requires relative not absolute values.

As per the CalCard.

 

[Murdoch]

I think you might be misunderstanding.
it is a device for "ongoing verification calibration" of your RCD tester in line with the requirements for use of instrument for test and inspection.

No calibration is necessary as its a verification device that requires relative not absolute values.

As per the CalCard.

as I said maybe I was misunderstanding .....

 

[boltonsparky]

Just done my calcard check on my meter this afternoon on one of your cards which is a great little idea.

The RCD ma setting on your machine. Mine starts at 10ma then 30, 100, 300, 500, 1000. It's a megger 1552 (yes an older MFT) not sure how that compares to the newer ones. Time settings seem logical to me but I find a lot of RCDs seem to trip around the 10ms area so might be worth having that option in there too. 

Ze Might be worth, if it's possible, using the most common 60898 B type values maybe. Although if it's to check ongoing calibration the values don't really matter I guess as you're checking against a known value and looking for change. 

Depending on price point it'd be good to have something with a Ze test function as in the past this has been the measurement that has wondered away from calibration on my previous meters. 

Back to RCDs with the newer types now available covering DC will your contraption include a DC test for RCDs too?

 

[binky]

I've always used a 'known RCD' for such purposes or just relied on getting multimeter cailbrated on a regular basis.

Something I've always been interested in, is a means of checking MCBs are working properly, especially old ones. WE have no means of knowing if an MCB would operate under fault conditions or not, and as some of the ones I encounter are 30/40 years old, that has to be doubtful at best. 

 

[Andy™]

Something I've always been interested in, is a means of checking MCBs are working properly, especially old ones. WE have no means of knowing if an MCB would operate under fault conditions or not, and as some of the ones I encounter are 30/40 years old, that has to be doubtful at best. 

good idea. maybe it could also be used to test fuses

 

[Geoff1946]

good idea. maybe it could also be used to test fuses

If it blows at rating times X  it was a good one?    

 

[NozSpark]

How about adding RDDC emulation??

 

[calltronics]

Thank you for all your replies. Especially boltonsparky

Yes, it does the DC level values. In line with new specifications.

Not so sure of your suggestion at testing fuses, it is a bit of a onetime test is it not ?!

As for MCB testing, not sure if the overload test incurs repeat damage to the MCB. Plus, how big would the load have to be for a 32A MCB? You would have to carry a brick sized heat sink.

 

[Geoff1946]

As for MCB testing, not sure if the overload test incurs repeat damage to the MCB. Plus, how big would the load have to be for a 32A MCB? You would have to carry a brick sized heat sink.

 I think an MCB test may be best done "out of circuit", using a low voltage source. This would allow a relatively low energy tester and avoid or at least reduce potential arc damage to the MCB contacts.

Is there any evidence that  in-service testing is actually needed?

 

[phil d]

I already own one of these 'check boxes' and to be honest the biggest pain in the arse was having to install the special socket to use it which makes it's usefullness somewhat limited.

For those who haven't used one let me briefly explain how they work, the idea is this, you have your meter calibrated professionally and then on getting it back you run it through the 'box', and record the results, there are a series of resistance values for both low ohms and IR tests, there is also one for earth loop impedance, in the case of my device it has two settings, source loop value and source loop plus one ohm, it also has facility to test the RCD test on the meter.

So, we have just had our tester returned from the calibration house and connect it to our box, we run the tests and note the values, if this is done on a weekly basis we are able to spot any error in our equipment, all very well and good, but why does it need a special socket I hear you ask, simple, if it isn't connected to a non rcd protected outlet you cannot perform high current loop tests, or indeed RCD tests, as it trips the device feeding the circuit.

Now in my own home it wasn't a problem, I simply fitted a round pin socket marked 'test equipment only' on it's own breaker (no rcd) adjacent to the consumer unit, but as I said earlier, it does limit the usefullness of the tester, say a freind wanted to borrow it, they'd need a non RCD protected supply too, I did try connecting it to an isolating transformer, but that was no use, the initial value of loop was too low as to be read, plus it adds a lot of weight, as I said, in my case it wasn't an issue, but it's hardly practical for someone who was say going working away for a few months.

 

[Andy™]

if it isn't connected to a non rcd protected outlet you cannot perform high current loop tests, or indeed RCD tests, as it trips the device feeding the circuit.

easy way around that. and if its being sold as a calibration / check box, id expect it to be wired in such a way that it wont trip other RCD's. if it does trip other RCD's then quite simply it isnt fit for purpose

 

[phil d]

easy way around that. and if its being sold as a calibration / check box, id expect it to be wired in such a way that it wont trip other RCD's. if it does trip other RCD's then quite simply it isnt fit for purpose

Exactly what I thought, there was nothing in the manual about it needing to be connected to a none RCD supply, I am not too bothered now, I bought it off a guy who was coming off the tools so I got it for about a quarter of the 'new' price, and it had hardly been used.

 

[calltronics]

Hi,

That was the prime reason for designing this unit.

It has no effect on the circuit it is pluged into. It will not trip the instalation.

It emulates an RCD and provides the same test results (ie time and trip current) no matter where you plug in into.

I use the mains supply for power only.

One point that has been raised is the the interface to conect to an instrument is a mains plug.

Should I also include 4mm test sockets?

 

[phil d]

personally i'd do one or the other, either a 13a socket or 4mm sockets, it keeps it smaller, does it do loop values too?

 

[calltronics]

personally i'd do one or the other, either a 13a socket or 4mm sockets, it keeps it smaller, does it do loop values too?

Yeh, it simulates the values: -  25, 5, 1, 0.5Ω

Which I think is fairly representative of various types of installations.

 

[Sidewinder]

@calltronics, I will let this go, but, I am unhappy about it because this is fundamentally advertising and you are no longer a forum sponsor which is unfair on those who are , plus it robs the forum of much needed funding for it to continue.