UK Do MFTs that test Type A/AC also test type F, type S, and Type G RCDs

[Jefferson steelflex]

Just bought an ethos 8400 mft, it's very simple, but as a trainee just wanted to know if it's possible to test Type A, AC, F, S,G RCDs with this tester, it says it tests only type S and type G.

So I'm just a bit confused.

 

[Andy78]

The type S and G referred to on your tester will be for Selective or General types, ie time delayed or not.

This is different and additional to the current characteristics of RCD type such as AC, A, F, and B.

Looking online quickly I think your tester is capable of testing type AC and A.

 

[Andy78]

I've popped this up as it's good reading regarding RCD types

RCD handbook

General RCD information

www.electriciansforums.net

 

[Jefferson steelflex]

The type S and G referred to on your tester will be for Selective or General types, ie time delayed or not.

This is different and additional to the current characteristics of RCD type such as AC, A, F, and B.

Looking online quickly I think your tester is capable of testing type AC and A.

Thanks for your message Andy, so does that mean I can test Type F, and Type S RCDs? I'm aware I'd need a higher range rcd testing mft to test Type b.

Also, I tried to open the rcd resource you uploaded but it says I'm not allowed to download

 

[pc1966]

I could download it today OK.

There is an updated version here though:

The RCD Handbook - Guide to The Selection and Application of Residual Current Devices (RCDs)

www.beama.org.uk

no idea how stable that URL is, so a copy on this site would be a good idea!

 

[Andy78]

Thanks for your message Andy, so does that mean I can test Type F, and Type S RCDs? I'm aware I'd need a higher range rcd testing mft to test Type b.

Also, I tried to open the rcd resource you uploaded but it says I'm not allowed to download

No idea about my resource I'm afraid, but the link by pc1966 works.

I think it's vital you look at the differences between RCD types as you seem to be mixing them up a bit.

Your tester will test type AC and A, but I don't think it will test type B or F.
It will likely test both AC and A in either general or selective setting.

 

[pc1966]

That is an interesting point: is testing on a AC/A waveform sufficient for a B or F RCD?

I would argue that it is, as you are not characterising the RCD as you might in a development lab, but simply verifying that it is detecting current at the appropriate level, and then disconnecting in the acceptable time-scale.

While I guess there might just be some corner-case fault that would removed DC/HF detection and leave AC trip OK, or you might have a knock-off module that fakes its B/F rating and really is an AC RCD inside, but I guess those are probably very rare situations to worry about.