Bi directional protection devices

[binky]

thought this was an interesting watch.

 

[Fleeting]

Good video that.

 

[truffle pig]

Good helpful video, however, by replacing an RCBO with a MCB & RCD would only be satisfactory if the RCD is bidirectional

 

[runningpiglet]

Yes, my understanding is this arises from modern RCDs and RCBOs and AFDDs being chock full of electronics which in some designs get upset if the terminals they had disconnected remain still energised. To get A B or F (or arc) sensitivity requires electronics in the breaker. Older units with type AC sensitivity often had no electronics - just the imbalance sense coil, some timing and a trip so weren't bothered which terminals remained live after opening. Is that right?

 

[Ronski]

I'm not an electrician, but I watched an efixx video on this recently, they explained that if the rcbo tripped and the power remained on the output, it would burn out the coil for the relay.

The thing is that PV inverters stop generating when they lose grid connection, so surely they won't remain supplying power and this not burn out the relay coil???

When I had more solar added last year my CU was replaced, and I doubt very much that a bi-directional RCBO was used.

I will be having the electrician back in a month or two, so I will mention it to him, but it'd be interesting to get your thoughts.

 

[binky]

If pv burnt out coils I'm sure I would have seen that by now. The inverter shuts down in seconds, officially upto 3 seconds, but in reality much faster than that, on loss of mains supply. The contacts within the rcbo will be far enough apart to prevent any arcing, so I don't see how the coil could be affected, except perhaps with a serious DC fault within the inverter, except inverters have built in protection against that as well I believe.

 

[Murdoch]

Me thinks BEAMA are pushing for more product sales courtesy of regs updates

The question is “is this actually necessary”

Wonder if the next update will mandate dedicated double pole RCDs for PV like it does for EV points ?

 

[NozSpark]

The only change that I’ve noticed on the wiring diagram of the bi-directional RCD’s & RCBO’s is that the test button is also isolated when they’re switched off

 

[ProDave]

I have seen even an old school no electronics RCD go up in smoke when the input was connected to the output terminals.