Testing RCDs Confusing Information. Time Delay and B types.

Sparkymania said:

(1)
The On Site Guide, referring to RCD testing, has two different tripping times.
For BSEN 61008 & 61009 it’s 300mS and BS 4293 it’s 200mS. I have never been able to find the reason why the newer ones are allowed a longer trip time. Surely if 300mS is allowable for one it should be okay for the other, even if originally manufactured to trip within 200mS

If the BS 4293 RCDs don't trip in 200 ms, they don't meet the standard they were originally manufactured to, and the test specification for their production line test. The only thing we know, is, therefore, the RCD may be defective. That's all there is to it. This is nothing new ... it's been around since we moved from BS 4293 to BS EN 61008.

Sparkymania said:

The other thing is time delayed ones. For the BSEN it’s stated as 130 to 500mS but the test for the BS it’s stated as 50% of rated time delay plus 200mS to 100% of rated time plus 200mS. What is the “rated time delay”?. It can’t be the 200ms as this is the max trip time, not the rated time delay. It doesn't make sense if you use to 200ms as that is 300mS to 400mS.

Again, product standard differences.

Sparkymania said:

(2)
I haven’t yet come across a type B RCD but as my tester is capable I looked up the test in the manual (Megger MFT1700 series).
It says to do a type A first. Then you need 3 leads to do the B and only on times 1.
Okay so far as this suggests that it’s a special test only using smooth DC which was confirmed on doing a search on Google for this test.
The confusing thing, though, is that it states the result is in mA; not mS. No explanation for this.
There is nothing on YouTube about this test, which is surprising.

... and to do a Type A test, you need to do a Type AC test first.

This is all cleared up in the 9th Ed of GN3 (288 March 2022), the tests going forward are "Type AC only", 1/2 times and 1 times, 0 and 180º, record the longest 1 times trip time.

Rating of S type = 300ms for  BS 4293

50%of 300 = 150ms + 200ms = 350ms

100%of 300ms = 300ms+ 200ms = 500ms

so as long as the device trips between 350 -500ms then the device is acceptable.

BS 4293 is for an earlier version of RCDs which were electro-mechanical; BS EN 61009 and 61008 are electronic devices and assumed to be 'more reliable'

No idea what's  going on with the test results for type B RCDs

Thanks Paul. It seems strange that they state it the way they do. Why not just say 300mS to 400mS instead of 50%/100% plus 200mS if that's what they mean?

That's the sort of thing you do when the first value is variable. 300 to 400 seems a small difference between the higher and lower value. Are they really referring to the 200mS max trip time because I would not have called that the "rated time delay" but the "maximum trip time" of the non time delayed RCD?

Legh Where are you getting the 300mS for the BS4293? You referred to "S type" but that's only the BSEN types. The BS types are referred to as "time delayed". I know it's the same thing but the On Site Guide differentiates between them. Look at the reply I gave to Paul.