RCD/RCBO

[Chit]

Hi all,

I've read quite a few posts about RCD's and RCBO's - what is the actual difference between the 2? As I understand it, an RCBO is a type of RCD but has over-current protection built in - In layman's terms, what is this? Under which circumstances does this occur?

Is it more advisable to have RCDs or RCBOs? Or is that dependant on the usage of the circuit?

Thanks.

 

[riveralt]

http://en.wikipedia.org/wiki/Residual-current_device

 

[Chit]

Thanks for that - don't understand the over-current though? What is this? How does it occur? Are RCBOs the only way to combat this or are there other products which can be installed to combat this?

 

[sparkiemike]

http://en.wikipedia.org/wiki/Overcurrent

 

[Chit]

Paragraph headed "Mains power" -

http://en.wikipedia.org/wiki/Current_limiting

Does this mean the MCBs protect against over current?

 

[sparkiemike]

Yes, they do.

 

[EFLImpudence]

Yes.

MCB (Miniature Circuit Breaker) - does the same as a fuse.

RCCB (Residual Current Circuit Breaker) - detects Earth Leakage i.e. current flowing where it shouldn't.

RCBO (Residual Current (circuit) Breaker with Overload protection) - combines both of the above.

 

[Chit]

Good morning all,

just read the posts - does this mean that an RCD together with an MCB does the same job as an RCBO? Or is the RCBO the better device to use?

 

[riveralt]

Good morning all,

just read the posts - (a)does this mean that an RCD together with an MCB does the same job as an RCBO? Or (b) is the RCBO the better device to use?

Is this the last question?

(a) Yes
(b) Yes because if it trips only one circuit will go instead of several where the MCB and RCD are used side by side. No because if there is a fault it is more difficult to identify whether it is an overcurrent or earth leakage fault.

 

[Chit]

All becoming much clearer now - thanks for that.

I also read the following passage in the Wikipedia link - "In particular, an RCD alone will not detect overload conditions, phase to neutral short circuits or phase-to-phase short circuits"

Would using an RCD with an MCB detect these types of faults as these together would work as an RCBO?

Apologies for the lack of knowledge!

 

[securespark]

Yes!

RCD + MCB offers the same protection as RCBO.

HOWEVER......

In the case where an RCD protecting more than one circuit trips, more than one circuit will go down, whereas if an RCBO trips, only the circuit protected by that RCBO will fail.

RCBO's are the preferred solution, but the cost is much greater.

 

[Chit]

Cool - thanks all.