Have you read that Technical Bulletin?Why would anybody go the trouble of inventing and manufacturing a unidirectional device?
... which, as you observe, is not only the opposite of what the Wiring Matters article says, but also makes absolutely no sense (whereas the Wiring Matters text does), since if a device has "Load" written at one end (and presumably something like "Supply" at the other end), it surely is intended to be regarded as ("uni") directional', isn't it?
Quite so - particularly given that, as have been discussed, to design such a device (with no obvious purpose/advantage I can think of) would seeming be very difficult (hence probably also expensive)Why would anybody go the trouble of inventing and manufacturing a unidirectional device?
Have you read that Technical Bulletin?
Interesting", perhaps, but of no relevance in relation to bi-directional and uni-directional RCDs, regs 134.1.1 and 510.3 probably being two of the most vague/general regs in the whole book.Interestingly from that Technical Bulletin: ....
BS 7671 requires persons to employ good workmanship and to use proper materials, as a fundamental principle in Regulation 134.1.1. Additionally, the installation of electrical equipment must take account of the manufacturer’s instructions as stated in both Regulation 134.1.1 and Regulation 510.3. Contravening these requirements could be deemed to be non-compliant with BS 7671 and not following manufacturer’s instructions will invalidate any device certification and warranty.
In trying to make some sense of that statement (if it is correct), the only thing I can think of is that the devices they refer to can only be reset 'electronically (or, at least, cn only be reset when the electronics are powered. If that were the case then, if they were installed such that the electronics were being powered from the 'load' side of the device, it would be impossible to reset them, so that would be a good the reason they could only be installed 'one way around' - but the obvious way of removing that problem would be for there to be provision for purely 'mechanical' re-setting (which, I must admit, I always thought was the case).These compact RCBOs contain electronic components and are typically unidirectional. Arc fault detection devices (AFDDs) are also typically unidirectional.
That seems very short sighted bearing in mind it does indicate the reason this whole thread can exist.
It is obviously desirable that, when current may flow 'either way' (as in solar installations etc.) that RCDs are capable of detecting and dealing with residual currents in both directions.
If you did understand, you might well be the only one who didI am not sure I understand all this.
I think it can be done with AC but, as bernard suggested, would probably be very complicated, and it would not seem to make any sense to expend considerable effort to create something which, as far as I can see (unless I'm missing something, would serve no useful purpose. I know that, at least a high frequencies 'it can be done with AC' because, in my youth, I used "Standing Wave Ratio" meters, which were able to distinguish between signals travelling to an antenna (then called 'aerial' ) via it's feeder cable and reflected signals which were 'coming back in the same cable. I confess that I never really understood how they achieved that!Leaving aside the fact that it is 'alternating current' so presumably going both ways everywhere anyway. .... Through the RCD, the Line current and Neutral current (while alternating) go in different directions. If this were not the case the RCD would not and could not work as there would be no residual current.... So how does the RCD know which way the current is travelling as it only detects - or more correctly reacts to - the difference (residual) between the two.
One wouldn't think so.Also, would the RCD notice if the Line and Neutral conductors were swapped?
I'm not so sure about that, so would need to think more carefullyThis must reverse the direction in the RCD.
Seemingly not (assuming that Hager actually wrote that), as I observed in post #26 - which would seem pretty extraordinary.And - as per post #23, why don't Hager even know what bidirectional means?
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local