The Value of R.C.D.s

davezawadi (David Stone): 
 

You beat me zoom, I hope that was only one at a time! Old TVs were live chassis, but two of them at once were a serious risk depending on which way around the two-pin plug was inserted.

It didn't even have to be 2-pin plug - most TVs had the chassis connected to supply N - but a few models were designed to have the chassis connected to L instead (the give away was an isolating transformer on the aerial socket) - so one of each of those side-by-side could be very interesting if both on the same supply (isolated or not). A separate isolation transformer for each TV of course would be better (perhaps where the idea of a separated supply for one item of equipment comes from?)

   - Andy.

I know there's was one particular TV that had an auto transformer for its HT and most of the heater supply's except the efficency diode which was fed from the LOPT anyway with the plug in one way round the chassis was at mains  voltage the other way it was at 455 Volts DC can you imagine it bloody lethal  if one of those bites you

and later the hybrid semicondtor and valve sets, there was at least one  Phillips model with a bridge, so the negative chassis was L and then  N on alternate half cycles. There was another model from the same era that  had 2 thyristors to do some clever switch-mode like thing to get a regulated rail. If anything went wring with that it usually involved changing all the silicon and the electrolytics, before powering on again, if not you soon had a sad pile of dead bits, and a PCB with bits of coloured wire replacing the blown out tracks.

Oddly, even without RCDs we managed to live.

Mike.

 

Oddly, even without RCDs we managed to live.

I didn't.

Z.

More on the subject here……..

Do Landlords Need To Fit RCDs? Latest 2020 Regulations (electricblu.co.uk)

Z.

More what Z? Do you mean more doubt and uncertainty? In my experience, the only reason for any uncertainty is poor EICRs. I have seen many where the “Inspector” says that an RCD needs to be fitted without any specific information on the non-compliance, usually with a high quote for the work. There is zero data on how many people are “saved” by RCDs and going by the accident statistics there cannot be very many.

If an installation needs an RCD because of specific non-compliance then it seems that everyone wants to “Upgrade” the CU. This is not necessary or in many cases desirable. Why not just fit an RCD in the tails, job done in an hour and for £40 maximum for materials? But no that is apparently not good enough, and there is much hand waving. Almost immediately a new board full of RCBOs is “necessary”, for a cost of £600-£1000 at least, in Bristol anyway. Does this make the installation one tiny bit safer than a single RCD? It does not, so why is it apparently necessary? Then when you see the mess that is made trying to extend all the old wiring and trying to fit a new bigger board in a small space and even bonding all the pipework when this is not necessary, has anything improved at all?

Here is a good one too. An advert in a local ad magazine:

*** Electrical, NICEIC approved contractor and Domestic Installer. 

(I'm still not sure why you would be both, they are different in requirements)

Call in the Professionals

-Electrical Inspection Condition Reports (EICR)

Keep people safe with an inspection every 5 years

Would you trust that level of competence? They haven't even got the name right! The content will probably be equally imaginary.

Maybe because it’s not good practice to always put a single RCD on the supply to a consumer unit? 

And, Good practice has NOTHING to do with safety.

Why won’t you think safety is a consideration when deciding on installing a 30mA upfront RCD to a consumer unit?

What is happening here is a choice (Good practice maybe, possibly convenience) is being made by the installer without consultation with the customer, at the customer's expense, on the alleged grounds of safety when in fact it is convenience, or actually profit. This is fraud by any name because the reason is a lie. 314.1 is often cited, but this is about individual circuits, not RCDs, and relates to faults in the Installation not particularly connected appliances. If one took this implicitly it would mean that every circuit had to have a separate RCD, which is certainly not in the regulations anywhere. It is pushed as RCBOs by manufacturers, which can be helpful in some cases but are not mandated in any way. Good  Practice is often quoted, but which regulation uses those words, Good Workmanship is not the same thing at all?