rcbo type b and c

C can be used if Zs is within the parameters that ensure disconnections times are met.

Now get back on da lash.

Cheers

 

get back on the drink i think

 

cheers

 

The new OSG Ch. 7 Final Circuits permits Type C for only TNCS with limits on total cable length. It then seems to contradict itself in App. 8 Standard Circuit Arrangments by stating that Table 8A is applicable for Type C with no mention of type of earthing...

 

50Hz, you need to keep in mind the simple fact that type C max permitted Zs is HALF that of a type B. So using a type C in circuits where anything other than PME earthing exists limits the length of the circuit. 0.35 ohms declared max for PME, but thats quite a chunk of impedance for a type C for starters. Thats probably why the OSG Ch 7 reference exists. But a check on the measured Zs will determine the final choice anyway. Type C breakers become more critical for loop impedance in the larger sizes, 20A upwards, smaller breakers will have more headroom.

 

Thats one problem with the starbreaker c/u at the moment, only type C RCBOs available

 

No mate Type B's now available. I purchased and fitted one yesterday. I commented on it to the wholesaler who confirmed Crabtree 6A RCBO type B's readily in supply now.

 

UP, I understand the reasons why, but what I find hard to fathom is the conflicting info in the OSG. A bit more thought has obviously gone into Chap. 7 but not elsewhere

 

Thanks for that unphased, must have happened in the past few weeks, will get some

 

I can't at the moment see why it matters whether they are c or b The criteria is disconnection times and surely the rcd is controlling the disconection times not the mcb ?

 

Im glad you said that lokkars as I was just thinking the same, but dident want to say anything incase I was missing something. If it was a tt system then it would normally always be imposible to meet the mas zs permitted for the over current device and so an rcd would be used to meet the required disconnection times. So what difference does it make using a type B or c rcbo with a pme system.

 

And I'm glad you said that Propper, cause I wasn't sure if I was missing something either :^O

 

Well can someone explain what difference it makes then?

 

I'm with Lokkers and propper spark on this.RCD element of RCBO provides earth fault protection so earth loop not such an issue. Line loop value becomes the governing factor to ensure enough fault current is generated to operate the overcurrent protection. Thats my understanding anyway flawed or otherwise.

 

Fabregas, why such the wealth of knowledge but low post count?

Please share some of the water from your overflowing well of knowledge.



p.s maybe your the sort who just prefers to watch with little manual involvement, you know, like voyeurism

 

Big L I have to reserve my energy for my last minute equalizers

 

Ah, so everything about you is the real deal.

I get it

 

Yes, type B and type C characteristics determine how the mcb behaves under load conditions as well as fault conditions. Type C and D withstand surges from high current loads for short drations, such as on start up from motors. However, the RCD element of the RCBO ensures fault protection from earth faults. I would have thought line faults would trip anything due to high urrent generated by fault of negligible impedence so type B, C or D in this instance really of no consequence. So I am open to explanation of why type B and C RCBOs matter in domestic situations. Perhaps they don't?